The most important application of semiconductor lasers is, without doubt, optical communication, the backbone of the information age. In the past few decades, incoherent optical communication with conventional semiconductor lasers, the III-V distributed feedback (DFB) lasers, has successfully fulfilled the global demand for the data rate. However, in order to support the rapidly growing Internet traffic of the 21st century, the transition from incoherent to coherent optical communication is inevitable, requiring new types of lasers, as the conventional III-V DFB lasers lack the phase coherence needed to serve as the light sources in coherent optical communication. The existent alternatives with high phase coherence are external cavity lasers (ECLs) and fiber lasers, whose high price and bulky size effectively thwart the upgrade of the current communication networks. This is the main motivation for us to develop high-coherence semiconductor lasers.
\r\n\r\nTo achieve the goal, we shall rethink and redesign semiconductor lasers. Advanced modern fabrication technology helps us to turn bold ideas into reality. Not only do we build semiconductor lasers on hybrid platforms, but also engineer elaborately the optical mode to enhance the lasers\u2019 phase coherence. The newly developed semiconductor lasers, hybrid Si/III-V lasers, are the core of the entire thesis. Their design principles, fabrication process, properties and performance in the coherent optical communication system will be presented and discussed. The experimental results show the Si/III-V lasers' superiority to their conventional counterparts.
\r\n\r\nAside from possessing high phase coherence, the Si/III-V lasers have great potential to be the light sources on the integrated photonic platforms. The fundamental obstacle thwarting photonic integration is optical feedback, to which the conventional semiconductor lasers are very sensitive. Without the protection provided by optical isolators, which unfortunately cannot be fabricated on chip, the performance of the conventional III-V DFB lasers could get significantly degraded by optical feedback. The Si/III-V lasers, with their built-in high-Q resonators, are very robust against optical feedback and can function properly in the isolator-free coherent optical communication systems. Thus, the cost of future optical networks can be further reduced by monolithically integrating passive photonic devices such as modulators and demodulators with the Si/III-V lasers.
\r\n\r\nFinally, all the studies centered on laser coherence trigger us to think deeply about the underlying relation between different means of characterizing laser coherence. A rigorous mathematical relation, the Central Relation, has been derived here, which not only unveils the fundamental relation between laser lineshape and frequency noise power spectral density (PSD) but also provides new methods of frequency noise controlling like optical filtering.
", "doi": "10.7907/y85t-nj39", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:10538", "collection": "thesis", "collection_id": "10538", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10242017-104926655", "type": "thesis", "title": "The Coherence Collapse Regime of High-Coherence Si/III-V Lasers and the Use of Swept Frequency Semiconductor Lasers for Full Field 3D Imaging", "author": [ { "family_name": "Harfouche", "given_name": "Mark", "orcid": "0000-0002-4657-4603", "clpid": "Harfouche-Mark" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "The semiconductor laser is the linchpin of optical communication and is now also penetrating a wide spectrum of new applications such as biomedical sensing, coherent communication, metrology, and time keeping. These require a higher degree of temporal coherence than is available from the present generation. Recently, it has been proposed and shown that heterogeneously integrated lasers on silicon and InGaAsP can be used to design high coherence single mode lasers with a much narrower linewidth than their all InGaAsP counterparts. Unfortunately, these lasers suffer from large thermal impedances and their optical feedback characteristics have not yet been explored. In the first part of this thesis, we will explore how flip chip bonding can help decrease the thermal impedance of these lasers to improve their overall performance and show that these lasers can provide up to 20 dB of optical isolation compared to their all III-V counterparts.
\r\n\r\nIn the second part of this thesis, we will report on the use of commercially available semiconductor lasers, in conjunction with an optical modulator to obtain high-resolution tomographic images in one shot without any moving parts. The electronic control over the imaged depth of this novel tomographic imaging camera enables it to monitor arbitrary depth slices in rapid succession over a depth range limited only by the coherence length of the laser. Not only does this imaging modality acquire the transverse image intensity (x,y) distribution of the light reflected from a particular depth, but also the phase of the reflected light enabling imaging beyond the conventional depth of field of the lens. This has important implications in applications requiring high lateral resolution images where the shallow depth of field would often require mechanical scanning of the lens elements to change the imaged depth.
", "doi": "10.7907/Z9W66J07", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10540", "collection": "thesis", "collection_id": "10540", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10262017-003847721", "type": "thesis", "title": "Frequency Noise Control of Heterogeneous Si/III-V Lasers ", "author": [ { "family_name": "Kim", "given_name": "Dongwan", "orcid": "0000-0002-5661-2503", "clpid": "Kim-Dongwan" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Narrow-linewidth lasers have many applications including optical telecommunication, laser spectroscopy, atomic clocks, and light detection and ranging. Conventionally, narrow linewidth lasers have been realized in the form of fiber-based or solid-state lasers. These lasers are bulky and relatively expensive, limiting their usage as bench-top systems in laboratory environments. Historically, semiconductor lasers, also known as laser diodes, have served applications where size and cost are important factors, including fiber optic communications. The linewidth of the semiconductor lasers, however, has been limited to the MHz-level, due to high loss in laser cavities and small size.
\r\n\r\nRecently, reduction of the frequency fluctuations in the semiconductor lasers has been achieved, obtaining tens of kHz linewidth, using the heterogeneous Silicon/III-V platform with a new design strategy. In this design, the majority of the optical energy is stored in the low-loss high-Q silicon resonator away from the high-loss III-V active region, requiring the minimal gain from the active region to overcome the reduced modal loss.
\r\n\r\nThis work explores the new design strategy further, and demonstrates theoretically and experimentally that the strategy eliminates the frequency fluctuations arising from the amplitude-phase coupling by placing a relaxation resonance frequency at frequencies of a few hundred MHz. Consequently, it becomes possible to obtain a semiconductor laser device possessing sub-kHz quantum-limited linewidths at frequencies of a few GHz (the frequencies of interest in optical telecommunication).
\r\n\r\nIn addition to the frequency noise reduction, the strategy turns out to have the additional benefit of accomplishing a coherent and stable lasing operation, even under external reflections. Thus, the new design strategy has the potential to replace the costly, but currently indispensable external optical isolators, which have been traditionally used to maintain the consistent performance of semiconductor lasers in the presence of external reflection.
\r\n\r\nThis work paves the way for the design of narrow-linewidth and stable semiconductor lasers that can function without the use of the bulky and costly external components, such as external cavities or optical isolators.
", "doi": "10.7907/Z90Z71G6", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:9597", "collection": "thesis", "collection_id": "9597", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03022016-094235703", "type": "thesis", "title": "Advanced Monte Carlo Simulation and Machine Learning for Frequency Domain Optical Coherence Tomography", "author": [ { "family_name": "Zhao", "given_name": "Sinan", "clpid": "Zhao-Sinan" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Ng", "given_name": "Willie", "clpid": "Ng-Willie" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical Coherence Tomography(OCT) is a popular, rapidly growing imaging technique with an increasing number of bio-medical applications due to its noninvasive nature. However, there are three major challenges in understanding and improving an OCT system: (1) Obtaining an OCT image is not easy. It either takes a real medical experiment or requires days of computer simulation. Without much data, it is difficult to study the physical processes underlying OCT imaging of different objects simply because there aren't many imaged objects. (2) Interpretation of an OCT image is also hard. This challenge is more profound than it appears. For instance, it would require a trained expert to tell from an OCT image of human skin whether there is a lesion or not. This is expensive in its own right, but even the expert cannot be sure about the exact size of the lesion or the width of the various skin layers. The take-away message is that analyzing an OCT image even from a high level would usually require a trained expert, and pixel-level interpretation is simply unrealistic. The reason is simple: we have OCT images but not their underlying ground-truth structure, so there is nothing to learn from. (3) The imaging depth of OCT is very limited (millimeter or sub-millimeter on human tissues). While OCT utilizes infrared light for illumination to stay noninvasive, the downside of this is that photons at such long wavelengths can only penetrate a limited depth into the tissue before getting back-scattered. To image a particular region of a tissue, photons first need to reach that region. As a result, OCT signals from deeper regions of the tissue are both weak (since few photons reached there) and distorted (due to multiple scatterings of the contributing photons). This fact alone makes OCT images very hard to interpret.
\r\n\r\nThis thesis addresses the above challenges by successfully developing an advanced Monte Carlo simulation platform which is 10000 times faster than the state-of-the-art simulator in the literature, bringing down the simulation time from 360 hours to a single minute. This powerful simulation tool not only enables us to efficiently generate as many OCT images of objects with arbitrary structure and shape as we want on a common desktop computer, but it also provides us the underlying ground-truth of the simulated images at the same time because we dictate them at the beginning of the simulation. This is one of the key contributions of this thesis. What allows us to build such a powerful simulation tool includes a thorough understanding of the signal formation process, clever implementation of the importance sampling/photon splitting procedure, efficient use of a voxel-based mesh system in determining photon-mesh interception, and a parallel computation of different A-scans that consist a full OCT image, among other programming and mathematical tricks, which will be explained in detail later in the thesis.
\r\n\r\nNext we aim at the inverse problem: given an OCT image, predict/reconstruct its ground-truth structure on a pixel level. By solving this problem we would be able to interpret an OCT image completely and precisely without the help from a trained expert. It turns out that we can do much better. For simple structures we are able to reconstruct the ground-truth of an OCT image more than 98% correctly, and for more complicated structures (e.g., a multi-layered brain structure) we are looking at 93%. We achieved this through extensive uses of Machine Learning. The success of the Monte Carlo simulation already puts us in a great position by providing us with a great deal of data (effectively unlimited), in the form of (image, truth) pairs. Through a transformation of the high-dimensional response variable, we convert the learning task into a multi-output multi-class classification problem and a multi-output regression problem. We then build a hierarchy architecture of machine learning models (committee of experts) and train different parts of the architecture with specifically designed data sets. In prediction, an unseen OCT image first goes through a classification model to determine its structure (e.g., the number and the types of layers present in the image); then the image is handed to a regression model that is trained specifically for that particular structure to predict the length of the different layers and by doing so reconstruct the ground-truth of the image. We also demonstrate that ideas from Deep Learning can be useful to further improve the performance.
\r\n\r\nIt is worth pointing out that solving the inverse problem automatically improves the imaging depth, since previously the lower half of an OCT image (i.e., greater depth) can be hardly seen but now becomes fully resolved. Interestingly, although OCT signals consisting the lower half of the image are weak, messy, and uninterpretable to human eyes, they still carry enough information which when fed into a well-trained machine learning model spits out precisely the true structure of the object being imaged. This is just another case where Artificial Intelligence (AI) outperforms human. To the best knowledge of the author, this thesis is not only a success but also the first attempt to reconstruct an OCT image at a pixel level. To even give a try on this kind of task, it would require fully annotated OCT images and a lot of them (hundreds or even thousands). This is clearly impossible without a powerful simulation tool like the one developed in this thesis.
", "doi": "10.7907/Z9X63JVM", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:8991", "collection": "thesis", "collection_id": "8991", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042015-232226135", "primary_object_url": { "basename": "Thesis_Yaakov_Vilenchik_2015.pdf", "content": "final", "filesize": 2835041, "license": "other", "mime_type": "application/pdf", "url": "/8991/1/Thesis_Yaakov_Vilenchik_2015.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Narrow-Linewidth Si/III-V Lasers: a Study of Laser Dynamics and Nonlinear Effects", "author": [ { "family_name": "Vilenchik", "given_name": "Yaakov", "clpid": "Vilenchik-Yaakov" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Narrow-linewidth lasers play an important role in a wide variety of applications, from sensing and spectroscopy to optical communication and on-chip clocks. Current narrow-linewidth systems are usually implemented in doped fibers and are big, expensive, and power-hungry. Semiconductor lasers compete favorably in size, cost, and power consumption, but their linewidth is historically limited to the sub-MHz regime. However, it has been recently demonstrated that a new design paradigm, in which the optical energy is stored away from the active region in a composite high-Q resonator, has the potential to dramatically improve the coherence of the laser.
\r\n \r\nThis work explores this design paradigm, as applied on the hybrid Si/III-V platform. It demonstrates a record sub-KHz white-noise-floor linewidth. It further shows, both theoretically and experimentally, that this strategy practically eliminates Henry\u2019s linewidth enhancement by positioning a damped relaxation resonance at frequencies as low as 70 MHz, yielding truly quantum limited devices at frequencies of interest.
\r\n\r\nIn addition to this empirical contribution, this work explores the limits of performance of this platform. Here, the effect of two-photon-absorption and free-carrier-absorption are analyzed, using modified rate equations and Langevin force approach. The analysis predicts that as the intra-cavity field intensity builds up in the high-Q resonator, non-linear effects cause a new domain of performance-limiting factors. Steady-state behavior, laser dynamics, and frequency noise performance are examined in the context of this unique platform, pointing at the importance of nonlinear effects.
\r\n\r\nThis work offers a theoretical model predicting laser performance in light of nonlinear effects, obtaining a good agreement with experimental results from fabricated high-Q Si/III-V lasers. In addition to demonstrating unprecedented semiconductor laser performance, this work establishes a first attempt to predict and demonstrate the key impact of nonlinear effects on silicon-based lasers.
", "doi": "10.7907/Z9513W57", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8254", "collection": "thesis", "collection_id": "8254", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05212014-113511509", "primary_object_url": { "basename": "Steger-S-T-electronic-updated.pdf", "content": "final", "filesize": 4202621, "license": "other", "mime_type": "application/pdf", "url": "/8254/1/Steger-S-T-electronic-updated.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "A Fundamental Approach to Phase Noise Reduction in Hybrid Si/III-V Lasers", "author": [ { "family_name": "Steger", "given_name": "Scott Tiedeman", "clpid": "Steger-Scott-Tiedeman" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Spontaneous emission into the lasing mode fundamentally limits laser linewidths. Reducing cavity losses provides two benefits to linewidth: (1) fewer excited carriers are needed to reach threshold, resulting in less phase-corrupting spontaneous emission into the laser mode, and (2) more photons are stored in the laser cavity, such that each individual spontaneous emission event disturbs the phase of the field less. Strong optical absorption in III-V materials causes high losses, preventing currently-available semiconductor lasers from achieving ultra-narrow linewidths. This absorption is a natural consequence of the compromise between efficient electrical and efficient optical performance in a semiconductor laser. Some of the III-V layers must be heavily doped in order to funnel excited carriers into the active region, which has the side effect of making the material strongly absorbing.
\r\n\r\nThis thesis presents a new technique, called modal engineering, to remove modal energy from the lossy region and store it in an adjacent low-loss material, thereby reducing overall optical absorption. A quantum mechanical analysis of modal engineering shows that modal gain and spontaneous emission rate into the laser mode are both proportional to the normalized intensity of that mode at the active region. If optical absorption near the active region dominates the total losses of the laser cavity, shifting modal energy from the lossy region to the low-loss region will reduce modal gain, total loss, and the spontaneous emission rate into the mode by the same factor, so that linewidth decreases while the threshold inversion remains constant. The total spontaneous emission rate into all other modes is unchanged.
\r\n\r\nModal engineering is demonstrated using the Si/III-V platform, in which light is generated in the III-V material and stored in the low-loss silicon material. The silicon is patterned as a high-Q resonator to minimize all sources of loss. Fabricated lasers employing modal engineering to concentrate light in silicon demonstrate linewidths at least 5 times smaller than lasers without modal engineering at the same pump level above threshold, while maintaining the same thresholds.
", "doi": "10.7907/91CD-6H86", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:7820", "collection": "thesis", "collection_id": "7820", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06032013-060508409", "primary_object_url": { "basename": "Arseny_Vasilyev_Thesis_CompleteThesis.pdf", "content": "", "filesize": 10762891, "license": "other", "mime_type": "application/pdf", "url": "/7820/1/Arseny_Vasilyev_Thesis_CompleteThesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Optoelectronic Swept-Frequency Laser and Its Applications in Ranging, Three-Dimensional Imaging, and Coherent Beam Combining of Chirped-Seed Amplifiers", "author": [ { "family_name": "Vasilyev", "given_name": "Arseny", "clpid": "Vasilyev-Arseny" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis explores the design, construction, and applications of the optoelectronic swept-frequency laser (SFL). The optoelectronic SFL is a feedback loop designed around a swept-frequency (chirped) semiconductor laser (SCL) to control its instantaneous optical frequency, such that the chirp characteristics are determined solely by a reference electronic oscillator. The resultant system generates precisely controlled optical frequency sweeps. In particular, we focus on linear chirps because of their numerous applications. We demonstrate optoelectronic SFLs based on vertical-cavity surface-emitting lasers (VCSELs) and distributed-feedback lasers (DFBs) at wavelengths of 1550 nm and 1060 nm. We develop an iterative bias current predistortion procedure that enables SFL operation at very high chirp rates, up to 10^16 Hz/sec. We describe commercialization efforts and implementation of the predistortion algorithm in a stand-alone embedded environment, undertaken as part of our collaboration with Telaris, Inc. We demonstrate frequency-modulated continuous-wave (FMCW) ranging and three-dimensional (3-D) imaging using a 1550 nm optoelectronic SFL.
\r\n\r\nWe develop the technique of multiple source FMCW (MS-FMCW) reflectometry, in which the frequency sweeps of multiple SFLs are \"stitched\" together in order to increase the optical bandwidth, and hence improve the axial resolution, of an FMCW ranging measurement. We demonstrate computer-aided stitching of DFB and VCSEL sweeps at 1550 nm. We also develop and demonstrate hardware stitching, which enables MS-FMCW ranging without additional signal processing. The culmination of this work is the hardware stitching of four VCSELs at 1550 nm for a total optical bandwidth of 2 THz, and a free-space axial resolution of 75 microns.
\r\n\r\nWe describe our work on the tomographic imaging camera (TomICam), a 3-D imaging system based on FMCW ranging that features non-mechanical acquisition of transverse pixels. Our approach uses a combination of electronically tuned optical sources and low-cost full-field detector arrays, completely eliminating the need for moving parts traditionally employed in 3-D imaging. We describe the basic TomICam principle, and demonstrate single-pixel TomICam ranging in a proof-of-concept experiment. We also discuss the application of compressive sensing (CS) to the TomICam platform, and perform a series of numerical simulations. These simulations show that tenfold compression is feasible in CS TomICam, which effectively improves the volume acquisition speed by a factor ten.
\r\n\r\nWe develop chirped-wave phase-locking techniques, and apply them to coherent beam combining (CBC) of chirped-seed amplifiers (CSAs) in a master oscillator power amplifier configuration. The precise chirp linearity of the optoelectronic SFL enables non-mechanical compensation of optical delays using acousto-optic frequency shifters, and its high chirp rate simultaneously increases the stimulated Brillouin scattering (SBS) threshold of the active fiber. We characterize a 1550 nm chirped-seed amplifier coherent-combining system. We use a chirp rate of 5*10^14 Hz/sec to increase the amplifier SBS threshold threefold, when compared to a single-frequency seed. We demonstrate efficient phase-locking and electronic beam steering of two 3 W erbium-doped fiber amplifier channels, achieving temporal phase noise levels corresponding to interferometric fringe visibilities exceeding 98%.
", "doi": "10.7907/YD38-BT07", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7812", "collection": "thesis", "collection_id": "7812", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312013-213433052", "primary_object_url": { "basename": "JS_Thesis.pdf", "content": "final", "filesize": 8183664, "license": "other", "mime_type": "application/pdf", "url": "/7812/1/JS_Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "On-Chip Integrated Label-Free Optical Biosensing", "author": [ { "family_name": "Sendowski", "given_name": "Jacob Benjamin", "clpid": "Sendowski-Jacob-Benjamin" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis investigates the design and implementation of a label-free optical biosensing system utilizing a robust on-chip integrated platform. The goal has been to transition optical micro-resonator based label-free biosensing from a laborious and delicate laboratory demonstration to a tool for the analytical life scientist. This has been pursued along four avenues: (1) the design and fabrication of high-$Q$ integrated planar microdisk optical resonators in silicon nitride on silica, (2) the demonstration of a high speed optoelectronic swept frequency laser source, (3) the development and integration of a microfluidic analyte delivery system, and (4) the introduction of a novel differential measurement technique for the reduction of environmental noise.
\r\n\r\nThe optical part of this system combines the results of two major recent developments in the field of optical and laser physics: the high-$Q$ optical resonator and the phase-locked electronically controlled swept-frequency semiconductor laser. The laser operates at a wavelength relevant for aqueous sensing, and replaces expensive and fragile mechanically-tuned laser sources whose frequency sweeps have limited speed, accuracy and reliability. The high-$Q$ optical resonator is part of a monolithic unit with an integrated optical waveguide, and is fabricated using standard semiconductor lithography methods. Monolithic integration makes the system significantly more robust and flexible compared to current, fragile embodiments that rely on the precarious coupling of fragile optical fibers to resonators. The silicon nitride on silica material system allows for future manifestations at shorter wavelengths. The sensor also includes an integrated microfluidic flow cell for precise and low volume delivery of analytes to the resonator surface. We demonstrate the refractive index sensing action of the system as well as the specific and nonspecific adsorption of proteins onto the resonator surface with high sensitivity. Measurement challenges due to environmental noise that hamper system performance are discussed and a differential sensing measurement is proposed, implemented, and demonstrated resulting in the restoration of a high performance sensing measurement.
\r\n\r\nThe instrument developed in this work represents an adaptable and cost-effective platform capable of various sensitive, label-free measurements relevant to the study of biophysics, biomolecular interactions, cell signaling, and a wide range of other life science fields. Further development is necessary for it to be capable of binding assays, or thermodynamic and kinetics measurements; however, this work has laid the foundation for the demonstration of these applications.
", "doi": "10.7907/2H9Y-AB63", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7800", "collection": "thesis", "collection_id": "7800", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312013-151934307", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 9140424, "license": "other", "mime_type": "application/pdf", "url": "/7800/1/Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "High-Coherence Hybrid Si/III-V Semiconductor Lasers", "author": [ { "family_name": "Santis", "given_name": "Christos Theodoros", "orcid": "0000-0001-8636-1613", "clpid": "Santis-Christos-Theodoros" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The relentlessly increasing demand for network bandwidth, driven primarily by Internet-based services such as mobile computing, cloud storage and video-on-demand, calls for more efficient utilization of the available communication spectrum, as that afforded by the resurging DSP-powered coherent optical communications. Encoding information in the phase of the optical carrier, using multilevel phase modulationformats, and employing coherent detection at the receiver allows for enhanced spectral efficiency and thus enables increased network capacity. The distributed feedback semiconductor laser (DFB) has served as the near exclusive light source powering the fiber optic, long-haul network for over 30 years. The transition to coherent communication systems is pushing the DFB laser to the limits of its abilities. This is due to its limited temporal coherence that directly translates into the number of different phases that can be imparted to a single optical pulse and thus to the data capacity. Temporal coherence, most commonly quantified in the spectral linewidth \u0394\u03bd, is limited by phase noise, result of quantum-mandated spontaneous emission of photons due to random recombination of carriers in the active region of the laser.
\r\n\r\nIn this work we develop a generically new type of semiconductor laser with the requisite coherence properties. We demonstrate electrically driven lasers characterized by a quantum noise-limited spectral linewidth as low as 18 kHz. This narrow linewidth is result of a fundamentally new laser design philosophy that separates the functions of photon generation and storage and is enabled by a hybrid Si/III-V integration platform. Photons generated in the active region of the III-V material are readily stored away in the low loss Si that hosts the bulk of the laser field, thereby enabling high-Q photon storage. The storage of a large number of coherent quanta acts as an optical flywheel, which by its inertia reduces the effect of the spontaneous emission-mandated phase perturbations on the laser field, while the enhanced photon lifetime effectively reduces the emission rate of incoherent quanta into the lasing mode. Narrow linewidths are obtained over a wavelength bandwidth spanning the entire optical communication C-band (1530-1575nm) at only a fraction of the input power required by conventional DFB lasers. The results presented in this thesis hold great promise for the large scale integration of lithographically tuned, high-coherence laser arrays for use in coherent communications, that will enable Tb/s-scale data capacities.
", "doi": "10.7907/M4KJ-8H56", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7074", "collection": "thesis", "collection_id": "7074", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05242012-174045229", "primary_object_url": { "basename": "Thesis_HsiChunLiu.pdf", "content": "final", "filesize": 2427683, "license": "other", "mime_type": "application/pdf", "url": "/7074/1/Thesis_HsiChunLiu.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Theory and Experiment of Slow-Light Coupled-Resonator Structures", "author": [ { "family_name": "Liu", "given_name": "Hsi-Chun", "clpid": "Liu-Hsi-Chun" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Slow light has been an inter-disciplinary topic and a rapidly growing area, especially over the last decade with the improvement of fabrication technology. The ability to slow down and control the group velocity of light may find applications such as optical buffers, optical delay lines, and enhanced light-matter interaction in optical modulator, amplifier, detectors, lasers, and nonlinear optics. The spirit of slow light is to replace a bulky device with a much shorter, compact structure.
\r\n\r\nThis thesis explores the design and experiment of coupled-resonator optical waveguides (CROWs), which consist of arrays of optical resonators in which light propagates through the coupling between resonators. The group velocity of light is dictated by the inter-resonator coupling strength. Light can be significantly slowed down if the inter-resonator coupling is weak. CROWs can be realized with various types of resonators. This thesis focuses on grating resonators in silicon waveguides, including grating-defect resonators and bandgap-modulated resonators. With the strong gratings, the grating resonators are only a few microns long. We control the inter-resonator coupling via the number of holes between adjacent resonators.
\r\n\r\nThe major limitations in the realization of CROWs have been various kinds of transmission losses, including the resonator losses, the discontinuity between CROWs and the coupling waveguides, and the fabrication disorder. These transmission losses limit the achievable group velocity and the maximum number of resonators. We address these transmission losses throughout this thesis. The resonator losses are overcome with the design and optimized fabrication of tapered grating-defect resonators and bandgap-modulated resonators. The discontinuity between CROWs and waveguides is reduced by tailoring the coupling along the CROW for adiabatic conversion. The optimization of the CROW response leads to the study of filter design based on CROW. Filter design formalism based on coupled-mode theory is presented. The effect of fabrication disorder on CROWs is analyzed, and the Butterworth filters are shown to be more robust against fabrication disorder. The fabrication and measurement of grating CROWs are presented, featuring high-Q (Q=105) grating resonators, coupling of up to 50 resonators, control of group velocity between c/13 and c/49, and Butterworth filters.
\r\n\r\nFinally, an optical analog of electromagnetically induced transparency is presented. The structure consists of two co-spatial gratings imposed on a three-mode waveguide. One of the supermodes, the Dark mode, possesses a group velocity which depends on the ratio of the grating strengths. The group velocity can be nearly zero if the two grating strengths are nearly identical.
\r\n", "doi": "10.7907/GVBF-4T29", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6364", "collection": "thesis", "collection_id": "6364", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04292011-221312708", "type": "thesis", "title": "Optoelectronic Control of the Phase and Frequency of Semiconductor Lasers", "author": [ { "family_name": "Satyan", "given_name": "Naresh", "clpid": "Satyan-Naresh" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis explores the precise control of the phase and frequency of the output of semiconductor lasers (SCLs), which are the basic building blocks of most modern optical communication networks. Phase and frequency control is achieved by purely electronic means, using SCLs in optoelectronic feedback systems, such as optical phase-locked loops (OPLLs) and optoelectronic swept-frequency laser (SFL) sources. Architectures and applications of these systems are studied.
\r\n\r\nOPLLs with single-section SCLs have limited bandwidths due to the nonuniform SCL frequency modulation (FM) response. To overcome this limitation, two novel OPLL architectures are designed and demonstrated, viz. (i) the sideband-locked OPLL, where the feedback into the SCL is shifted to a frequency range where the FM response is uniform, and (ii) composite OPLL systems, where an external optical phase modulator corrects excess phase noise. It is shown, theoretically and experimentally, and in the time and frequency domains, that the coherence of the master laser is \u201ccloned\u201d onto the slave SCL in an OPLL. An array of SCLs, phase-locked to a common master, therefore forms a coherent aperture, where the phase of each emitter is electronically controlled by the OPLL. Applications of phase-controlled apertures in coherent power-combining and all-electronic beam-steering are demonstrated.
\r\n\r\nAn optoelectronic SFL source that generates precisely linear, broadband, and rapid frequency chirps (several 100 GHz in 0.1 ms) is developed and demonstrated using a novel OPLL-like feedback system, where the frequency chirp characteristics are determined solely by a reference electronic oscillator. Results from high-sensitivity biomolecular sensing experiments utilizing the precise frequency control are reported. Techniques are developed to increase the tuning range of SFLs, which is the primary requirement in high-resolution three-dimensional imaging applications. These include (i) the synthesis of a larger effective bandwidth for imaging by \"stitching\" measurements taken using SFLs chirping over different regions of the optical spectrum; and (ii) the generation of a chirped wave with twice the chirp bandwidth and the same chirp characteristics by nonlinear four-wave mixing of the SFL output and a reference monochromatic wave. A quasi-phase-matching scheme to overcome dispersion in the nonlinear medium is described and implemented.
\r\n", "doi": "10.7907/24DM-VW62", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:5780", "collection": "thesis", "collection_id": "5780", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05072010-002329705", "primary_object_url": { "basename": "Xiankai.Sun_thesis_simplex_printing.pdf", "content": "final", "filesize": 1974789, "license": "other", "mime_type": "application/pdf", "url": "/5780/1/Xiankai.Sun_thesis_simplex_printing.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Supermode Si/III-V Lasers and Circular Bragg Lasers", "author": [ { "family_name": "Sun", "given_name": "Xiankai", "orcid": "0000-0002-9137-0298", "clpid": "Sun-Xiankai" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Semiconductor lasers are arguably the most important component in optical communications. This thesis investigates two types of semiconductor lasers that are useful in integrated optics. Part I focuses on supermode Si/III\u2013V lasers and Part II discusses circular Bragg lasers for the application as surface-emitting lasers.
\r\n\r\nJust as optical fibers have largely replaced the traditional copper wires in long-distance applications, people started to consider incorporating optical communication onto chips, primarily because the increased ohmic heating and RC delay associated with the metal interconnection prevent further increase in the data-processing rate. Si is well known to be the integration platform for electronics, and III\u2013V materials (GaAs, InP, etc.) are efficient light emitters. It is natural to bring them together to realize the on-chip optical communication. Among various Si/III\u2013V integration schemes the most promising is the hybrid Si evanescent platform in which a wafer-bonding technique that is compatible with current CMOS processing is used to bring Si and III\u2013V materials together. Part I of this thesis focuses on the application of a novel mode-control method to such hybrid waveguide system to enhance the modal gain, which makes for more efficient and, most importantly, shorter devices that may hold the key to the photonics/electronics integration. The supermode theory is derived, the shortest adiabatic mode transformer is theoretically and numerically studied, and the device design and fabrication are presented, followed by the experimental demonstration of the performance enhancement in the mode-controlled Si/InGaAsP laser devices.
\r\n\r\nVertical cavity surface emitting lasers are a commercial light source for optical communications, but their single-modedness and good emission pattern are guaranteed only over a very small mode area (diameter of several microns) thus they have limitations in high-power applications. As an alternative, circular Bragg lasers can be designed as a superior surface emitting laser that produces high output power with good beam quality. Part II of this thesis presents a comprehensive and systematic theoretical study on the surface-emitting Hankel-phased circular Bragg lasers in various geometries. The analytical and numerical mode-solving methods will be described, followed by near- and above-threshold modal analyses.
", "doi": "10.7907/6797-0136", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:2215", "collection": "thesis", "collection_id": "2215", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05282008-162123", "primary_object_url": { "basename": "linzhu_thesis.pdf", "content": "final", "filesize": 5368793, "license": "other", "mime_type": "application/pdf", "url": "/2215/1/linzhu_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Photonic Crystal Bragg Lasers: Design, Fabrication, and Characterization", "author": [ { "family_name": "Zhu", "given_name": "Lin", "clpid": "Zhu-Lin" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "On-chip, single mode semiconductor lasers are usually fabricated using conventional distributed feedback (DFB) structures. Due to the limitation of index guiding in the transverse direction, the width of these lasers has to be less than a few microns. Meanwhile, the laser output power is limited by catastrophic optical damage (COD) at the facets and thus large optical cavities are necessary for high power semiconductor lasers. Therefore, high power, single mode applications are challenging, due to the conflicting requirements for large modal volume (to prevent COD by reducing optical power density) and narrow width (to obtain the single mode operation). Increasing the width of single mode semiconductor lasers is fundamentally important for obtaining high spectral and spatial optical power densities.
\r\n\r\nThis thesis reports on achieving the single mode operation of large area, edge emitting semiconductor lasers, using the photonic crystal Bragg structure (two dimensional distributed feedback structure). Both theoretical and experimental results are presented. Two dimensional coupled mode approaches and transfer matrix methods are developed to analyze and design the photonic crystal Bragg structure. It is shown that the single mode lasing can be obtained by satisfying both the transverse and longitudinal Bragg conditions and a single lobe, diffraction limited far field can be obtained by optimizing the coupling coefficient of the photonic crystal.
\r\n\r\nElectrically pumped, large-area (100 um x 500 um), single mode semiconductor photonic crystal Bragg lasers are experimentally demonstrated in pulsed and continuous wave conditions with single lobe, diffraction limited far fields. Two dimensional lasing wavelength tuning is demonstrated, which proves that the lasing mode is truly defined by the photonic crystal lattice. Furthermore, a wavelength tuning sensitivity about 80 times smaller than a conventional DFB laser is also achieved, allowing for more accurate control of the lasing wavelength.
\r\n\r\nPhotonic crystal lasers based on effective index guiding are also studied. Single mode operation is achieved by combining the transverse confinement provided by an effective index guiding mechanism with the longitudinal mode selection provided by the Bragg reflection from the photonic crystal cladding. These devices represent an important first step toward using photonic crystals in a different way for the modal control of semiconductor lasers in planar optical circuits.
\r\n\r\n\r\n", "doi": "10.7907/7MMN-7Q15", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:1184", "collection": "thesis", "collection_id": "1184", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03272008-143400", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 3825487, "license": "other", "mime_type": "application/pdf", "url": "/1184/16/thesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Study of Optical Phase Lock Loops and the Applications in Coherent Beam Combining and Coherence Cloning", "author": [ { "family_name": "Liang", "given_name": "Wei", "clpid": "Liang-Wei" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical Phase-Lock loops (OPLLs) have potential applications in phase coherent optics including frequency synthesis, clock distribution and recovery, jitter and noise reduction, etc. However, most implemented OPLLs are based on solid state lasers, fiber lasers, or specially designed semiconductor lasers, whose bulky size and high cost inhibit the applications of OPLLs.
\r\n\r\nSemiconductor lasers have the advantages of low cost, small size, and high efficiency. In this thesis, I report on a study of OPLLs using commercial SCLs, and explore their novel applications in coherent beam combining and coherence cloning.
\r\n\r\nIn chapter 1-3, I will first introduce the theory of OPLLs and presents the experimental study of OPLLs made of different commercial SCLs. To improve the performance of OPLLs, electronic compensations using filter designs are also discussed and studied.
\r\n\r\nIn chapter 4-5, I will study the application of OPLLs in coherent beam combining. Using OPLLs, an array of slave lasers can be phase locked to the same master laser at the same frequency, their outputs can then be coherently combined. The phase variations of the element beams due to the optical path-length variations in fibers can be further corrected for by using multi-level OPLLs. This approach eliminates the use of the optical phase/frequency shifters conventionally required in a coherent beam combining system. In the proof of principle experiment, we have combined two lasers with a combining efficiency of 94% using the filled-aperture combining configuration. Furthermore, I will discuss the scalability of a cascaded filled-aperture combining system for the combination of a large number of lasers.
\r\n\r\nOPLLs can also be used to reduce the phase noise of SCLs by locking them to a low noise master laser. In chapter 6, I will describe the theory of coherence cloning using OPLLs and present the experimental measurements of the linewidths and frequency noises of a low noise fiber laser, a free-running and locked slave lasers.
\r\n\r\nIn chapter 7, the thesis concludes by proposing a novel OPLL configuration of large loop bandwidth and identifying future works that need to be done to advance the development of this technology.
", "doi": "10.7907/YHBF-KW11", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:2020", "collection": "thesis", "collection_id": "2020", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05242007-105741", "primary_object_url": { "basename": "PoonThesis.pdf", "content": "final", "filesize": 3158864, "license": "other", "mime_type": "application/pdf", "url": "/2020/1/PoonThesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Active and Passive Coupled-Resonator Optical Waveguides", "author": [ { "family_name": "Poon", "given_name": "Joyce Kai See", "clpid": "Poon-Joyce-Kai-See" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Bockrath", "given_name": "Marc William", "clpid": "Bockrath-M-W" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Coupled-Resonator Optical Waveguides (CROWs) are chains of resonators in which light propagates by virtue of the coupling between the resonators. The dispersive properties of these waveguides are controllable by the inter-resonator coupling and the geometry of the resonators. If the inter-resonator coupling is weak, light can be engineered to propagate slowly in these structures. The small group velocities possible in CROWs may enable applications in and technologies for optical delay lines, interferometers, buffers, nonlinear optics, and lasers.
\r\n\r\nThis thesis reports on achieving and controlling the optical delay in passive and active CROWs. Both theoretical and experimental results are presented. Transfer matrices, tight-binding models, and coupled-mode approaches are developed to analyze and design a variety of coupled resonator systems in the space, frequency, and time domains. Although each analytical method is fundamentally different, in the limit of weak inter-resonator coupling these approaches are consistent with each other. From these formalisms, simple expressions for the delay, loss, bandwidth, and a figure of merit are derived to compare the performance of CROW delay lines. Using a time-domain tight-binding model, we examine the resonant gain enhancement and spontaneous emission noise in amplifying CROWs to find that the net amplification of a propagating wave does not always vary with the group velocity but instead depends on the termination and excitation of the CROW.
\r\n\r\nCROWs in the form of high-order (> 10) weakly coupled passive polymer microring resonators were fabricated and measured. The measured transmission, group delay, and dispersive properties of the CROWs agreed with the theoretical results. Delays in excess of 100 ps and slowing factors of about 25 over bandwidths of about 20 GHz were observed. The main limitation of the passive CROWs was the optical losses. To overcome the losses and to enable electrical integration, we demonstrated active CROWs in the form of current injection InP-InGaAsP Fabry-Perot laser arrays. Even though the losses could be completely compensated, the transmission spectra and signal-to-noise ratio depended strongly on the injection current and resonator position. The signal-to-noise ratio degraded rapidly away from the input. Our results highlight possible avenues to operate laser arrays as loss-compensated or amplifying CROWs.
", "doi": "10.7907/MX8K-9V82", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:636", "collection": "thesis", "collection_id": "636", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02142007-151137", "primary_object_url": { "basename": "Choi_jm_2007.pdf", "content": "final", "filesize": 2712042, "license": "other", "mime_type": "application/pdf", "url": "/636/1/Choi_jm_2007.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Design, Fabrication, and Characterization of Semiconductor Transverse Bragg Resonance Lasers", "author": [ { "family_name": "Choi", "given_name": "John Myun", "clpid": "Choi-John-Myun" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Bockrath", "given_name": "Marc William", "clpid": "Bockrath-M-W" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Controlling the spatial modes of a laser cavity is fundamental for improving the beam quality of a laser and achieving highly efficient coupling of power into an optical system. High-power applications are particularly challenging due to the conflicting requirements for large modal volume, to prevent facet damage by reducing energy density, and narrow width, for single-mode operation of an index-guided waveguide. By replacing traditional index confinement with Bragg reflection in the transverse direction, single-mode operation can be achieved even for large modal volumes. These grating confined structures, transverse Bragg resonance (TBR) waveguides, have the unique ability to support localized modes above the light line. Such modes normally couple to radiation modes of the cladding when the confinement mechanism is total-internal-reflection and are too lossy to be considered guided modes. However, for Bragg resonance confined modes, the modal loss can be designed by careful optical mode engineering to introduce a large loss discrimination that can favor a single spatial, low-loss mode. Semiconductor TBR lasers in an InP/InGaAsP/InGaAs material system were designed, fabricated, and characterized to investigate this property. Two regions of operation are identified for TBR waveguides, and, while transverse mode selection is provided by a grating, longitudinal mode control is found to be also necessary to restrict operation to the region that supports modes above the light line.", "doi": "10.7907/NG25-BN55", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:2242", "collection": "thesis", "collection_id": "2242", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05292005-111904", "primary_object_url": { "basename": "W_Green_thesis_final.pdf", "content": "final", "filesize": 6389623, "license": "other", "mime_type": "application/pdf", "url": "/2242/1/W_Green_thesis_final.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "InGaAsP-InP Semiconductor Microcavity Geometries for Annular Bragg Reflection, Optical Switching, and Sensing", "author": [ { "family_name": "Green", "given_name": "William M. J.", "clpid": "Green-William-M-J" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "One of the key mandates of modern optoelectronic research is the development of compact photonic integrated circuits, capable of performing many diverse functions for the generation, manipulation, and detection of light, all on a single chip. A key practical requirement for such circuits is the development of optical devices for the localization and processing of light within extremely small dimensions. In recent years, planar microring and microdisk resonators, in which light is confined by total internal reflection, have emerged as versatile photonic elements for filling this role. The high quality factors and long photon storage times associated with the whispering-gallery modes supported by these microcavities result in several technologically useful characteristics, including narrow-band filter response, and large resonant enhancement of the circulating electric field. These properties have been exploited in numerous passive and active device applications, including optical add/drop multiplexers, all-optical switches, and tunable lasers.
\r\n\r\nThis thesis describes the study of several unique ring-based optical microcavity geometries based upon the indium gallium arsenide phosphide/indium phosphide alloy semiconductor material system, undertaken in an effort to explore new optoelectronic architectures for confining and manipulating light.
\r\n\r\nThe first portion of this work involves the analysis and demonstration of a new microcavity geometry, in which cylindrical Bragg reflection is used for radial optical confinement, as an alternative to total internal reflection. In this class of structures, collectively known as annular Bragg resonators, light can be guided within a ring or pillar defect layer surrounded by cylindrical Bragg mirrors. Several microcavities based upon this configuration are designed and fabricated using a thin InGaAsP quantum well membrane. Using pulsed optical excitation, the characteristics of these structures as low threshold vertically emitting lasers is explored.
\r\n\r\nSecond, a total internal reflection-based coupled waveguide-resonator geometry, having applications to low power optical switching and modulation, is analyzed. This geometry makes use of the hybrid integration of a Mach-Zehnder interferometer with a racetrack resonator. Switching takes place using the Mach-Zehnder to control the coupling parameters in the vicinity of the critical coupling condition. Characterization of the static and dynamic output response of a thermooptically actuated InGaAsP-InP hybrid switch device demonstrates good ON-OFF switching contrast, microsecond response time, and reduced switching power in comparison with a conventional Mach-Zehnder configuration.
\r\n\r\nFinally, this work concludes by examining both the annular Bragg resonator and hybrid switch geometries in application to chemical and biological sensing. Both microcavity devices are shown to possess unique characteristics making them ideal for sensitive monitoring of small changes in the refractive index of a chemical or biological analyte.
", "doi": "10.7907/GGH2-AQ53", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:1717", "collection": "thesis", "collection_id": "1717", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05102005-112605", "primary_object_url": { "basename": "GTPaloczi_PhD_Thesis.pdf", "content": "final", "filesize": 7131872, "license": "other", "mime_type": "application/pdf", "url": "/1717/1/GTPaloczi_PhD_Thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Polymer Integrated Optics: Device Architectures and Fabrication Methods", "author": [ { "family_name": "Paloczi", "given_name": "George T.", "clpid": "Paloczi-George-T" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Bockrath", "given_name": "Marc William", "clpid": "Bockrath-M-W" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Polymer materials are becoming increasingly important for integrated photonic circuits in optical communications networks. The optical and mechanical properties of polymers for integrated optics are explored in this thesis and it is shown that the manipulation of these properties leads to developments that in other optical materials could not be achieved as quickly or as easily, or not achieved at all.
\r\n\r\nSo that the benefits of a large range of operating wavelengths due to low material dispersion in polymers, are not lost to the wavelength dependence of optical couplers, we design wavelength-invariant couplers using a geometrical representation of coupled mode theory. Simulations of the resulting couplers confirm a virtually constant response over a large range of input wavelengths.
\r\n\r\nThe direct-write ability of electron beam sensitive polymers enables rapid fabrication of high-precision optical devices. Microring resonator optical filters and a compact microring-based inline reflector are fabricated by this method and characterized. Chaining multiple rings together results in the coupled resonator optical waveguide (CROW). A CROW-Mach-Zehnder interferometer is fabricated and the measured response corresponds well with the predictions based on the matrix theory.
\r\n\r\nPolymer materials can be patterned by a variety of methods not possible with traditional optical materials. Soft-stamp replica molding presents a means to further reduce the costs of implementing polymer materials. Demonstrating the potential of the method, microring resonators are fabricated, with excellent agreement between the responses of the original and the replica. To further demonstrate the effectiveness of the process, it is applied in the fabrication of Mach-Zehnder modulators. The modulators exhibit excellent properties, with single-arm modulation voltages of 8 V and extinction ratios better than 19 dB. Successive repetition of the molding process allows for multilayer polymer optical devices. Finally, the flexible properties of polymers are exploited for pliable, all-polymer freestanding optical circuits.
", "doi": "10.7907/W41G-2374", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:21", "collection": "thesis", "collection_id": "21", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01042005-110346", "type": "thesis", "title": "Bragg Reflection in Optical Waveguides", "author": [ { "family_name": "Ouyang", "given_name": "George Xiaoxi", "clpid": "Ouyang-George-Xiaoxi" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In this dissertation I explore the phenomenon of Bragg reflection in optical waveguides. Two specific waveguide structures are studied in detail: the Bragg fiber and a generic planar waveguide with a Bragg grating etched in it.
\r\n\r\nBragg fibers can be classified into two groups: the air-core Bragg fiber and the coaxial Bragg fiber. Whereas the former has a plain air core at the center, the latter contains an additional high-index column in the core. Using a perturbative approach I study and compare the dispersion properties of the two types of fibers, with special attention to their potential for truly single-mode transmission. As the result a large single-mode frequency window, which also includes a zero-dispersion point, is found for the TM mode in the coaxial fiber.
\r\n\r\nThe air-core Bragg fiber is also studied as a potential candidate for dispersion compensation. It is found that Bragg reflections in the fiber are capable of producing negative dispersion values at least as large as -20,000 ps/(nm\u2022km), which is a twenty-fold improvement over previous results. The fiber parameters used for this study are somewhat unrealistic however, and further improvement is necessary before a Bragg fiber can be deployed as a Dispersion Compensating Fiber (DCF).
\r\n\r\nOptical filters based on Bragg grating structures also involve Bragg reflections. While continuous Fiber Bragg Gratings (FBG's) have long been studied and deployed as practical reflection filters, the possibility of etching a discrete grating in a (planar) waveguide has to my knowledge, never been investigated. In this dissertation I propose a novel scheme for designing such a grating, which is implemented by discretizing its continuous counterpart into a series of air holes. The relationship between the two gratings (discrete and continuous) is established in terms of the grating strength and the local grating period.
", "doi": "10.7907/31V8-1J13", "publication_date": "2004", "thesis_type": "engd", "thesis_year": "2004" }, { "id": "thesis:1813", "collection": "thesis", "collection_id": "1813", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05152003-144457", "primary_object_url": { "basename": "thesis_mookherjea.pdf", "content": "final", "filesize": 4999524, "license": "other", "mime_type": "application/pdf", "url": "/1813/1/thesis_mookherjea.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Coupled-Resonator Optical Waveguides and Multiplexed Solitons", "author": [ { "family_name": "Mookherjea", "given_name": "Shayan", "orcid": "0000-0001-9864-2367", "clpid": "Mookherjea-Shayan" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Cohen", "given_name": "Donald S.", "clpid": "Cohen-D-S" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Whether over micron-long or kilometer-long distances, periodic phenomena can strongly affect both the propagation and the confinement of optical pulses. Periodicities can be engineered through the structural design of optical waveguides, or they may manifest self-consistently from induced nonlinear polarizations. In light of recent developments in fabrication technologies for semiconductor waveguides, polymeric materials, and optical fiber, we show that both strongly- and weakly-nonlinear channels are promising for new devices and systems in optical communications. This thesis proposes and discusses applications of guided wave periodicities in the framework of photonic crystals (coupled-resonator optical waveguides as well as transverse Bragg resonance waveguides and amplifiers), nonlinear phenomena in photorefractive semiconductors, and the nonlinear evolution of temporal solitons in dispersion-managed fibers.
\r\n\r\nCoupled-resonator optical waveguides (CROWs) are composed of a periodic array of electromagnetic resonators, typically on the micron or sub-micron length scales. A photon in such a waveguide sees a periodic potential, and according to the Floquet-Bloch theorems, has a wavefunction that reflects this periodicity. CROWs have a unique dispersion relationship compared to other semiconductor waveguides, and can be used to slow down the speed of propagation, enhance nonlinear interactions such as second-harmonic generation and four-wave mixing, and form frozen soliton-type field distributions that use the optical Kerr nonlinearity to stabilize themselves against decay via adjacent-resonator or waveguide-resonator coupling.
\r\n\r\nIn optical fibers that possess the optical Kerr nonlinearity in addition to group-velocity dispersion, it is possible to propagate pulses with envelopes that \"breathe\" with distance, typically at kilometer or longer length scales. Such waveforms are characterized by a set of parameters, e.g., amplitude, chirp, etc., that vary in a periodic manner as the pulse propagates. Borrowing an idea from field theory, e.g., of classical pendulums, or quantum-mechanical elementary particles, the pulse envelope may be viewed as a particle traversing a trajectory in a phase space defined by its characteristic parameters. Distinct, non-overlapping trajectories are assigned as symbols of a multilevel communication code. Since it is the periodicity, arising from the Kerr nonlinearity, that generates this diversity in phase-space, there is no analog of this multiplexed system in linear optical transmission links. The overall bit-rate can be improved several fold above the current limits.
", "doi": "10.7907/9BYR-7J64", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:7", "collection": "thesis", "collection_id": "7", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01032005-131558", "type": "thesis", "title": "Analytical and Numerical Studies of Waveguiding and Coupling in Periodic Dielectric Materials", "author": [ { "family_name": "Xu", "given_name": "Yong", "orcid": "0000-0001-5849-032X", "clpid": "Xu-Yong-Physics" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Mabuchi", "given_name": "Hideo", "clpid": "Mabuchi-H" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Using both analytical approaches and finite difference time domain simulations, we investigate different types of waveguiding and coupling mechanisms, including direct coupling between the optical resonators, waveguide-resonator coupling, indirect resonator coupling via waveguide modes, and Bragg reflection in cylindrically symmetric geometries.
\r\n\r\nBy coupling an array of high Q optical resonators together, we form a new type of waveguide, coupled resonator optical waveguide (CROW), where photons propagate by \"hopping\" from one resonator to its nearest neighbors. Using tight-binding approximation, we find that the CROW band dispersion can be simply characterized by a coupling coefficient \u03ba. The tight-binding results are confirmed by using the finite difference time domain algorithms to analyze two examples of CROW\u2019s: one is composed of coupled defect cavities in a two-dimensional triangular lattice photonic crystal, while the other is formed by coupling an array of dielectric microdisk cavities.
\r\n\r\nBy coupling a resonator to a waveguide, we significantly change the reflection and transmission characteristics of the waveguide. The waveguide dispersion can also be drastically modified by coupling an array of resonators to the waveguide, due to indirect coupling between the resonators via waveguide modes. Using a formalism based on the quantum scattering theory, we investigate how the waveguide-resonator coupling, resonator gain (loss), degeneracy and symmetries of the resonator modes influence the optical properties of such coupled waveguide-resonator systems.
\r\n\r\nBragg guiding can be achieved in cylindrically symmetric geometries by using cladding media with alternating high and low refractive indices. Examples include Bragg fibers and dielectric coaxial fibers. An asymptotic formalism is developed to study the dispersion, propagation loss, and field distribution of guided modes in such fibers. The results are compared with those obtained from numerical calculations, where excellent agreement is found between the two approaches.
", "doi": "10.7907/9988-YR54", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:2525", "collection": "thesis", "collection_id": "2525", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06092005-103556", "primary_object_url": { "basename": "Koumans_rgmp_2001.pdf", "content": "final", "filesize": 9416033, "license": "other", "mime_type": "application/pdf", "url": "/2525/1/Koumans_rgmp_2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Semiconductor mode-locked lasers : modeling, characterization and applications", "author": [ { "family_name": "Koumans", "given_name": "Roger Gerard Matthias", "clpid": "Koumans-R-G-M" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes the modeling and characterization of mode-locked semiconductor lasers. An enhanced dynamic model is developed to describe the startup and steadystate behavior of mode-locked lasers. Two new applications for mode-locked lasers are given and their potential is discussed. A new technique to characterize the optical pulses emitted from a mode-locked laser is analyzed and demonstrated.\n\nA combined time and frequency-domain dynamic model is introduced for semiconductor mode-locked lasers. The model includes both linear mode-coupling effects through carrier density modulation at harmonics of the mode-spacing as well as nonlinear effects like gain saturation and additional mode-coupling through four wave mixing. The model is used to study the behavior of a 2 mm long mode-locked semiconductor laser with a gain section of 1900 \u00b5m and an absorber section of 100 \u00b5m. Without the inclusion of spontaneous emission, steady state mode-locking is achieved after a few tens of nanoseconds producing chirped picosecond pulses. The inclusion of spontaneous emission disturbs the steady state mode-locking solution into a quasi-steady state which causes timing and amplitude jitter of the pulse train.\n\nThe potential of a semiconductor mode-locked laser with a dense mode spacing (~25 GHz) as an optical source for wavelength division multiplexing is studied. One of the locked modes is filtered out by a narrow band fiber Bragg grating and its use as a single wavelength source is examined. The bit error rate (BER) performance of the source is measured but no \"error free\" transmission is achieved due to mode competition noise. The laser is next used in an external feedback configuration where the feedback is provided by a fiber Bragg grating. Lasing only occurs when the fiber Bragg grating is tuned to one of the monolithic cavity modes leading to a discretely tunable single wavelength source whose channel spacing is determined by the mode spacing of the semiconductor laser. Single mode operation of the laser with more than 40 dB side mode suppression is obtained. The BER performance of several channels is examined by stretching the fiber Bragg grating. \"Error free\" performance is obtained for all channels.\n\nAs another new application, the use of semiconductor mode-locked lasers in a photonic analog to digital (A/D) converter is proposed. The method uses wavelength multiplicity to increase the sampling rate of A/D converters. The optical output of a number of semiconductor lasers each mode-locked at a different center wavelength is spectrally stitched and time-interleaved into a high repetition rate multi-wavelength sampling pulse train (MW-SPT) which can be used in a photonic A/D converter to sample a high-end microwave signal. The amplitude modulated high repetition rate MW-SPT is next wavelength demultiplexed into parallel pulse streams with a lower sampling rate which can be processed by conventional electronic state-of-the-art A/D converters in a parallel fashion.\n\nFinally, a new method for the characterization of ultrashort pulses called time resolved optical gating based on dispersive propagation (DP-TROG) is introduced and demonstrated. The DP-TROG technique is a new non-interferometric method for characterizing ultra-short optical pulses in amplitude and phase without the need for a short optical gating pulse. An algorithm is developed for the reconstruction of the pulse amplitude and phase from the measurements. The pulse train emitted from a mode-locked semiconductor laser at 1.5\u00b5m is characterized using this new technique and excellent pulse retrieval is achieved.\n", "doi": "10.7907/wx7b-6286", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:2568", "collection": "thesis", "collection_id": "2568", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06132005-083934", "primary_object_url": { "basename": "Provenzano_dr_2001.pdf", "content": "final", "filesize": 5016835, "license": "other", "mime_type": "application/pdf", "url": "/2568/1/Provenzano_dr_2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "From semiconductor lasers to fiber Bragg grating lasers in optical communications", "author": [ { "family_name": "Provenzano", "given_name": "Dan Raymond", "clpid": "Provenzano-D-R" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes the semiconductor laser signal and noise propagation effects in single mode fiber and fiber Bragg gratings. The capability to fabricate custom fiber Bragg gratings was developed, which enabled the design and fabrication of gratings for a number of applications. Finally, gratings were developed and specialized for use in a single mode fiber ring laser.\r\n\r\nA quantum mechanical description of laser noise is presented in order to discuss pump-noise suppressed semiconductor lasers capable of sub-shot noise, also known as \"squeezing.\" Experimental results for an 850 nm Fabry-Perot semiconductor laser are presented showing squeezing at room temperature of 29% below the shot noise limit measured using a balanced homodyne detector, corresponding to 41% below the standard quantum limit at the output facet of the laser. The side mode suppression ratio was varied with slight temperature tunings and correlated with the laser noise. It was found that the higher the sidemode suppression ratio, the lower the noise.\r\n\r\nNoise analysis was continued with 1540 nm distributed feedback semiconductor lasers. Laser parameters such as noise, chirp, and resonance frequency were characterized by propagation in dispersive fiber,and fitting the parameters to a model for the fiber. Again, a correlation was found between side mode suppression and laser noise, especially after several kilometers of propagation in fiber. The principles of signal and noise propagation were applied to fiber Bragg gratings. Theory and experiment indicated direct laser modulation enhancement by a uniform fiber Bragg grating by 7 dB at modulation frequencies, of up to 25 GHz, and also noise reduction of 2 dB at frequencies up to 15 GHz.\r\n\r\nFacilities were established to write and produce customized fiber Bragg gratings of various strengths in various fiber types as well as in ion-exchanged waveguides in bulk glasses. Analyses of writing times and strengths were performed and optimized for various applications. Uses for these gratings include dispersion compensation, noise reduction, beam or pulse shaping, and spectral filtering for dense wavelength division multiplexed (DWDM) optical networks. Amplitude and phase masks were developed and shown to produce arbitrarily apodized and chirped gratings.\r\n\r\nFiber gratings were next refined for use as key elements in a new type of single mode fiber ring laser. Some of the beneficial characteristics of this fiber laser include long cavity size (80 cm), 80 dB signal-to-noise ratio, high side mode suppression ratio, and white noise linewidth as narrow as 2 kHz. The laser noise was also nearly shot noise limited. This combination of low amplitude and low phase noise allowed the observation of extremely low noise enhancement after 50 km of standard, dispersive fiber up to 20 GHz frequency. A comparison was made between our fiber ring laser and a standard high grade distributed feedback semiconductor laser in transmitting 10 Gbits/sec data. Over a 50 km fiber, the fiber ring laser achieved the same signal to noise ratio with half the power as the semiconductor laser.\r\n", "doi": "10.7907/setx-7j50", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:6100", "collection": "thesis", "collection_id": "6100", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10052010-144834578", "primary_object_url": { "basename": "Peral_em_2000.pdf", "content": "final", "filesize": 53284556, "license": "other", "mime_type": "application/pdf", "url": "/6100/1/Peral_em_2000.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Some issues relevant to propagation of lightwave signals in optical fibers", "author": [ { "family_name": "Peral", "given_name": "Eva M.", "clpid": "Peral-E-M" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Fiber optics is a promising technology that can enable the high bit rates and long spans that are on increasing demand. Although the fiber bandwidth is as large as several terahertz, there are several phenomena, related to both intrinsic fiber properties and characteristics of the state-of-the-art transmitters and receivers, which seriously degrade the performance of fiber communication systems, imposing limits on the transmission bandwidths and distances that can be achieved.\r\n\r\nIn this thesis, some of the issues affecting linear and nonlinear propagation in optical fiber will be theoretically and experimentally studied. Schemes for compensation of some of these phenomena or amelioration of their effects will be presented.", "doi": "10.7907/PVBN-KY66", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:2540", "collection": "thesis", "collection_id": "2540", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06102005-082207", "primary_object_url": { "basename": "Lee_r_2000.pdf", "content": "final", "filesize": 11048866, "license": "other", "mime_type": "application/pdf", "url": "/2540/1/Lee_r_2000.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Lasing and modified spontaneous emission in photonic crystal structures and microcavities", "author": [ { "family_name": "Lee", "given_name": "Reginald K.", "clpid": "Lee-R-K" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\nSemiconductor light-emitting devices in the near-infrared (1.55 \u00b5m) based on microfabricated photonic crystal structures are demonstrated. The photonic structures consist of two-dimensional arrays of air holes patterned into an optically thin, airsuspended InGaAsP slab by high-resolution electron beam lithography and various dry etching techniques.\n\nTwo types of microcavities are examined. The first are larger hexagonally shaped cavities in the range of 10 to 20 \u00b5m in size and bounded by the photonic crystal structure. Cavity mode spontaneous emission at room temperature under optical pumping is used to demonstrate mode confinement due to the in-plane bandgap. No cavity mode peaks in the emission spectrum are seen if the in-plane bandgap is not spectrally aligned with the material emission. Pulsed lasing is also demonstrated with the lasing threshold at 66 mW peak incident optical pump power at a duty cycle of less than 1% in order to minimize membrane heating. Changes in the pump geometry is shown to result in controllable lasing mode switching. This behaviour is explained in terms of mode Q, lasing threshold and enhanced spontaneous emission into the mode.\n\nThe second type of microcavity consists of a single point defect into photonic lattice with a modal volume of [...]. Cavity quality factors up to 250 are demonstrated and suppressed spontaneous emission due to the bandgap except at the mode frequency is shown. Pulsed lasing at 143 K under optical pumping is demonstrated.\n\nThe fundamental modification of the spontaneous emission rate due to the in-plane bandgap in a photonic crystal slab structure with no microcavity is experimentally and numerically examined. Incomplete bandgaps are theoretically shown to be able to strongly inhibit spontaneous emission. High density of states points in the band-structure are seen to greatly enhance the spontaneous emission rate. Measurements using phase sensitive spectroscopy of the spontaneous emission rate from quantum wells in the photonic crystal slab show a greater than 10 times inhibition of the emission rate in the in-plane bandgap. Experimental evidence for saturation of the surface recombination at relatively low pumping levels is found.\n", "doi": "10.7907/kvvd-em02", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:2527", "collection": "thesis", "collection_id": "2527", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06092005-145119", "primary_object_url": { "basename": "Mcadams_ms_1998.pdf", "content": "final", "filesize": 5337589, "license": "other", "mime_type": "application/pdf", "url": "/2527/1/Mcadams_ms_1998.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Semiconductor laser signals and noise in fiber grating systems", "author": [ { "family_name": "McAdams", "given_name": "Matthew S.", "clpid": "McAdams-M-S" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis describes the effect of transmission through a fiber Bragg grating on the signal and noise properties of semiconductor laser light. We show that fiber gratings can be used to increase the modulation response of a laser, to improve the response of a laser/fiber system, or to decrease the intensity noise of a continuous-wave laser signal. The effects are the result of dispersive propagation and frequency discrimination, and depend on the nature of the grating and the laser dynamic properties. This connection is developed first by deriving the dynamic properties of semiconductor lasers, including the direct current modulation response, frequency chirp, and laser noise. The effect of propagation through an arbitrary medium is derived, with the conclusion that both dispersion and frequency discrimination result in conversion of frequency modulation into amplitude modulation and vice versa. These general results are applied to laser modulation and noise spectra to derive the transfer functions for dispersive optical fiber. Next we detail the experimental characterization of laser dynamics, from which we can determine the important laser parameters. We follow this with a discussion of fiber Bragg gratings and show that the phase of the grating transmittance, which is important in changing the characteristics of the signals being transmitted, can be inferred numerically from a measurement of the intensity transmission. Finally, we unite these topics with the demonstration of a 7 dB increase in the laser response at frequencies up to 25 GHz in transmission through a fiber grating. The result is well predicted by a numerical Fourier domain analysis of the laser signal and fiber grating. In addition, we investigate the effect of a fiber grating on the relative intensity noise (RIN) of a laser, showing that a model of grating as a linear frequency discriminator is sufficient for explaining much of the results. We show there exist conditions under which a grating can reduce the RIN, which depend on the phase relationship between correlated intensity and frequency fluctuations. We demonstrate a 2 dB reduction in RIN at frequencies up to 15 GHz. The combination of these effects is used in calculating signal-to-noise ratios for real systems incorporating gratings, and in showing that gratings can re-narrow pulses broadened by fiber dispersion.", "doi": "10.7907/9tcw-nq16", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:505", "collection": "thesis", "collection_id": "505", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02052008-083834", "primary_object_url": { "basename": "Tong_xl_1998.pdf", "content": "final", "filesize": 6858617, "license": "other", "mime_type": "application/pdf", "url": "/505/1/Tong_xl_1998.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Properties and applications of potassium lithium tantalate niobate", "author": [ { "family_name": "Tong", "given_name": "Xiaolin", "clpid": "Tong-Xiaolin" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes the physical and photorefractive properties of potassium lithium tantalate niobate (KLTN) single crystal material.\r\n\r\nThe top seeded solution growth method is reviewed. The phase transition temperatures and dielectric properties are related to the compositions of the KLTN crystals. A liquid/solid interface dynamics model is introduced to explain the experimental results which is that hydrogen ion concentration in KLTN crystals can be reduced dramatically by doping copper in the absence of titanium.\r\n\r\nDark conductivity of KLTN crystals are contributed by two species when the temperature is in the range of 250 K and 350 K. Two species are hydrogen ions and shallow trapped electrons (holes). These results have been confirmed by direct dc conductivity measurements and holograms fixing experiments. Hydrogen ion has two types of motion in the crystals: O-H vibration and O-H libration. We established a model to describe hydrogen ions motions and hopping in KLTN crystals. The theoretical prediction is in agreement with experimental results. Hologram thermal fixing for optical data storage is discussed. Hydrogen ions are identified as the mobile ion which is responsible for thermal fixing.\r\n\r\nIn ferroelectric phase KLTN crystals, spontaneous polarization of individual microdomains can be aligned throughout the entire crystal by the poling process. Photorefractive space charge fields play a role deploing the microdomains wherever space charge field opposing to spontaneous polarization. This may cause microdomain switching and lead to the generation of index grating. Experimental observation of Barkhausen current jumps is the signature of domain inversion.\r\n\r\nHolograms thermal fixing in potassium niobate crystals are also investigated. Because potassium niobate crystal has an orthognal structure with space group mm2, 3D polarization dependence of OH bands are observed. A special cut of iron doped potassium niobate crystal was designed to achieve the maximum exponential gain coefficient for thermal fixing of volume holograms. A significant enhancement of diffraction efficiency of the fixed grating 43% is measured.\r\n\r\nThe last part of this thesis discussed topological distribution of phase matching of three-wave mixing in biaxial crystals. Thirty possible distributions are illustrated. The optimum operating directions under phase matching condition in biaxial crystal can be obtained from the calculation of the effective nonlinear coefficients. A set of analytical expressions of effective nonlinear optical coefficient for the crystals with mm2 point group is given. The phase matching directions are in either x, y, or z plane in order to obtain maximum coefficient.", "doi": "10.7907/Y1N1-2V86", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:303", "collection": "thesis", "collection_id": "303", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01232008-110449", "primary_object_url": { "basename": "Engin_d_1998.pdf", "content": "final", "filesize": 4954646, "license": "other", "mime_type": "application/pdf", "url": "/303/1/Engin_d_1998.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Nonlinear spatial dynamics of double phase conjugation in photorefractive crystals and holographic dynamics of photopolymerization", "author": [ { "family_name": "Engin", "given_name": "Doruk", "clpid": "Engin-D" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Cross", "given_name": "Michael Clifford", "clpid": "Cross-M-C" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis explores spatial nonlinear optical effects in photorefractive crystals and photopolymers. In these materials upon exposure with spatially varying light, large refractive index changes occur. In the first part of the thesis Double Phase Conjugation in photorefractive crystals is studied both theoretically and experimentally. Various processes effecting the conjugation fidelity, such as fanning are quantified through a coupled multiple mode model which is an extension of the coupled mode theory. Predictions of the model such as phase conjugation is confirmed experimentally. Critical slowing down near the threshold is also predicted and experimentally confirmed. Lastly the amplitude equation formalism is carried out for the wave mixing phenomenon. This approach unifies the optical phenomenon with a large class of other physical phenomena referred to as pattern formation outside of equilibrium. Through this formalism the instability is identified as a convective instability and the possibility of a transition to absolute instability is studied.\n\nIn the second part of the thesis, photopolymerization dynamics is studied with holography. A theoretical model is developed for the holographic configuration starting from a standard chain polymerization model. A holographic characterization method is developed. The method is especially powerful in measuring diffusion constants. Various multifunctional polymers is characterized using the novel technique.\n", "doi": "10.7907/78gp-sz41", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:2426", "collection": "thesis", "collection_id": "2426", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06032005-160031", "primary_object_url": { "basename": "Feng_j_1997.pdf", "content": "final", "filesize": 4491879, "license": "other", "mime_type": "application/pdf", "url": "/2426/1/Feng_j_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Frequency chirp and spectral dynamics in semiconductor lasers", "author": [ { "family_name": "Feng", "given_name": "Jing", "clpid": "Feng-J" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A study of the effects of the longitudinal distribution of optical intensity and carrier density on the static and dynamic characteristics of semiconductor lasers has been performed. Through a self-consistent way, a static model for above threshold operation of a single mode distributed feedback (DFB) laser is developed by calculating the longitudinal optical intensity and carrier density distribution. A dynamic model for large signal modulation of the DFB laser is also presented based on time-dependent coupled-mode equation for electric traveling waves in the laser. The spatial hole burning (SHB) has been analyzed in a quarter wavelength shifted DFB laser and a conventional DFB laser.\n\nA small-signal model is developed by including the optical intensity and carrier density distributions. Expressions are derived for the intensity modulation and resonance frequency, the frequency chirp and FM modulation, and the linewidth enhancement factor. Theoretical analysis of the frequency chirp in the DFB lasers has been used to support our experimental results. The model has led us to a new understanding of frequency chirp in DFB lasers and discovery of the ultra small chirp lasers.\n\nThe spectral dynamics and high speed response of uncooled DFB lasers have been studied. The most distinguished element differentiating the uncooled DFB lasers from uncooled FP lasers is that in uncooled DFB lasers; the wavelength detuning plays an important role in determining their spectral and high speed characteristics at high temperatures. Comparing with lasers lasing at gain peak, the DFB lasers with large negative wavelength detune could have better high speed performance at room temperature, but they might have higher threshold current. We can achieve optimum performance of uncooled DFB lasers by choosing wavelength detuning properly based on the laser applications.", "doi": "10.7907/mahd-9t42", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:215", "collection": "thesis", "collection_id": "215", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01172008-101729", "primary_object_url": { "basename": "Salik_b_1997.pdf", "content": "final", "filesize": 5084906, "license": "other", "mime_type": "application/pdf", "url": "/215/1/Salik_b_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Spatio-temporal beam synthesis and applications to photolithography", "author": [ { "family_name": "Salik", "given_name": "Boaz", "clpid": "Salik-B" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis explores techniques for and applications of free-space beam shaping. After reviewing the basic principles of scalar diffraction theory, I discuss and experimentally demonstrate several approaches to two- and three-dimensional transverse beam synthesis; these include analytical solutions of varying complexity as well as methods for computer optimization of beams with arbitrary constraints. Analytical solutions are also presented for the temporal analogy of nondiffracting beams, i.e., nondispersing pulses, and repercussions to time-dependent diffraction theory are discussed.\n\nNext these beam shaping methods are applied to imaging photolithography, addressing ways to improve both resolution and focal depth therein with the use and proper design of phase masks. In this work it is evident that computation time plays a critical role in the applicability of phase masks to photolithography, because phase mask design algorithms tend to scale unfavorably with mask size. I therefore introduce an approximation to the Hopkins equation which reduces the computation time for partially coherent imaging by one to two orders of magnitude. Following this the question of spatial coherence in phase mask-assisted photolithography becomes interesting, and the optimal coherence for such systems is investigated both theoretically and experimentally. The properties of incoherent imaging are next applied to a slightly different problem--imaging through random media. A new technique for ballistic imaging is presented, discussed theoretically, simulated, and demonstrated experimentally, and its advantages and drawbacks are analyzed. Finally, a theoretical overview of the fundamental limits to space-time beam shaping is presented, several results of which are demonstrated.\n\nDue to the diversity of the subjects discussed, introductions and brief histories are given at the beginning of relevant chapters.", "doi": "10.7907/ws8q-mt53", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:5224", "collection": "thesis", "collection_id": "5224", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06072005-131657", "type": "thesis", "title": "Dynamics of Amplitude and Phase in Semiconductor Lasers and Effects of Propagation in Dispersive Optical Fibers", "author": [ { "family_name": "Marshall", "given_name": "William K.", "clpid": "Marshall-William-K" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Libbrecht", "given_name": "Kenneth George", "clpid": "Libbrecht-K-G" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The work described in this thesis occupies the region of overlap between the modulation, chirp, and noise properties of semiconductor lasers on one hand and dispersive propagation in optical fiber on the other. It is shown herein that simple relationships exist between the amplitude and phase variations of different kinds and that these relations lead to consequences of dispersive propagation which are different for the noise from semiconductor lasers than for the modulation. A range of topics related to the main theme of the interplay between laser chirp, amplitude-phase correlation, and dispersive propagation is considered. That there is much to be gained by understanding them together, as inter-related issues, is the overall conclusion.
\r\n\r\nFirst, changes in intensity variations which occur during dispersive propagation are described compactly in terms of a transfer function involving the relationship between amplitude and phase variations of the source. Then, the main dynamic characteristics of semiconductor lasers are described including the relationships between amplitude and phase variations produced by modulation and noise in semiconductor lasers. For an appropriate combination of laser and fiber parameters, it is demonstrated that the laser intensity noise can be reduced over a wide range of frequencies. It is also demonstrated that the change in relative intensity noise with propagation has a different dependence on laser and fiber parameters than does the change in modulation response. Next, the phenomenon of adiabatic compression of the gain and index of refraction in a semiconductor due to spectral hole burning is considered, clarifying some aspects of the commonly-used spectral hole burning model. Finally, the problem of the semiconductor laser and dispersive propagation of the output is re-examined within a quantum mechanical context and the input-output relations for the laser are explored.
", "doi": "10.7907/amwv-x166", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:1723", "collection": "thesis", "collection_id": "1723", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05112005-153655", "type": "thesis", "title": "Quantum well intersubband transition detection and modulation", "author": [ { "family_name": "Xu", "given_name": "Yuanjian", "clpid": "Xu-Yuanjian" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is a theoretical and experimental investigation of the intersubband transitions in quantum well structures. The I-V characteristics, infrared absorption spectra, and photoresponse spectra of superlattices are used to characterize multiple quantum well structure properties in unipolar devices.\r\n\r\nAn important numerical method for solving the problem of bound-to-continuum transitions, the transfer matrix method, is presented for the self-consistent calculations. Although the boundary conditions are relaxed due to the calculation self-consistentcy, inappropriate boundary conditions were previously included in the literature.\r\n\r\nThe first observation of the quantum interference effect in the photocurrent spectra is described using a weakly coupled bound-to-continuum transition quantum well structure and electric field domain formation in the device. This effect persists even at high biases where Kronig-Penny minibands of periodic superlattice potential in the continuum are destroyed. Using this observation, the electric field domain formation and the electron coherence length in superlattices were analyzed. A large off-resonant energy level alignment between two neighboring wells in the high field domain was observed. The effect of temperature on the transport properties was also discussed. As a further study of electric field domain formation in superlattices, an optical experiment using Stark effect is suggested.\r\n\r\nThe dependence of the absorption spectral linewidth of quantum well intersubband transitions on the electron population in the well is experimentally demonstrated using field-induced charge transfer and thermal-induced charge transfer in an asymmetric coupled quantum well structure. We show that this population-induced broadening is very important in the broadening of intersubband transitions in quantum well structures and that previously reported linewidth values for the contribution from donor scattering were overestimated. Many body effects and single-particle band non-parabolicity are the likely causes. An electronic light chopper based on population modulation was fabricated using the asymmetric coupled quantum well structure. A modulation depth of 45% has been demonstrated using 50 periods of the coupled well structure.\r\n", "doi": "10.7907/pbpa-dx11", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:55", "collection": "thesis", "collection_id": "55", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01072008-092000", "primary_object_url": { "basename": "Salvatore_ra_1996.pdf", "content": "final", "filesize": 5872847, "license": "other", "mime_type": "application/pdf", "url": "/55/1/Salvatore_ra_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Ultrashort and ultrahigh-repetition-rate pulses from passively mode-locked semiconductor lasers", "author": [ { "family_name": "Salvatore", "given_name": "Randal A.", "clpid": "Salvatore-R-A" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is an investigation into both the fundamental and experimental aspects of using semiconductor lasers to generate extremely short (100's of fs) and very high repetition frequency (> 50 GHz) optical pulses. The pulses are produced through modelocking, a technique of forcing a laser to operate in a number of optical modes simultaneously and to hold a constant phase relationship between these modes. Both the shortest and highest repetition rate pulses have been obtained from passive modelocking. An inherently nonlinear technique which does not use any active external timing source. Two structures, ridge-waveguide stripe lasers and liquid phase epitaxy (LPE) regrown lasers, were used to directly generate picosecond width pulses. Using cross-correlation techniques, pulse shape and phase measurements are made. Linear dispersion compensation is shown to achieve nearly a factor of 20 in pulse compression. Stable pulses down to 260 fs are generated.\n\nShowing that exitonic effects are not essential in these devices, wavelength tunability was combined with dispersion compensation to create the first broadly tunable subpicosecond semiconductor source. The device is found to give tunability ranges and mode-locked spectral widths that are comparable to the best results achieved in dye lasers in terms of fractions of the operating gain spectral width. Results for different regimes in the tuning range are examined, and pulses directly from the laser are found to have about a 2 to 1 fall-time to rise-time ratio. A significant nonlinear chirp is found only when the laser is tuned to the short wavelength side of its tuning range and was determined to cause long tails in the autocorrelations of compressed pulses. Additionally, spread-resistant pulses are described and experimentally analyzed.\n\nThe case of high-repetition-rate modelocking, which more likely involves about 5 modes instead of 5000 modes, is examined. Approximations in the leading theory of passive modelocking are shown to be inadequate in this case. A steady-state model for high-repetition-rate modelocking is developed including phase effects and is tailored to parameters of semiconductor lasers. Self-consistent solutions show that a lower threshold gain can exist for a supermode than for single mode operation. Predictions of the laser's behavior upon modifying key material, geometric, and bias parameters are made. Experimental results show that through adjustment of the gain current, \"chirp-controlled\" modelocking is obtained with operation in any of the three chirp regimes (up-chirped, chirp-free, or down-chirped). This pulse chirp and resulting broadening are due to the algebraic addition of opposite-signed chirps from saturation of the absorber and gain sections. Theoretical modelling from the supermode analysis also traverses the same chirp regimes when the photon intensity is increased.\n", "doi": "10.7907/1f05-ek48", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:2514", "collection": "thesis", "collection_id": "2514", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06082005-110714", "primary_object_url": { "basename": "Orlov_ss_1996.pdf", "content": "final", "filesize": 6033886, "license": "other", "mime_type": "application/pdf", "url": "/2514/1/Orlov_ss_1996.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Holographic storage dynamics, phase conjugation, and nonlinear optics in photorefractive materials", "author": [ { "family_name": "Orlov", "given_name": "Sergei S.", "clpid": "Orlov-S-S" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis explores the application of photorefractive materials in two distinct areas: the holographic data storage and the dynamic nonlinear optical interactions. First, we have established that partial ferroelectric domain reversal in certain ferroelectric materials can be used to permanently fix the dynamic holographic gratings, and analyzed the interaction between the fixed and the dynamic components of a hologram. A comprehensive analysis of the storage temporal dynamics in photorefractive materials is further developed for the case of thermal ionic fixing. An experimental study of holographic storage dynamics in photorefractive lithium niobate revealed new features related to the ionic conductivity in this and similar materials. We established and developed techniques for long-lifetime and high-efficiency hologram fixing in the holographic data storage applications. We further analyze theoretically the impact of the recording response properties of different storage media (including photorefractive materials and photopolymers) and optical detection noise on the ultimate storage capacity of holographic memories.\n\nSecond, the transverse properties of the photorefractive double phase conjugate mirror (DPCM) have been studied. We have established that the DPCM exhibits a sharp conjugation fidelity gain threshold which increases with image resolution, while the reflectivity is a smoothly varying function of nonlinear gain. The conjugation fidelity was found to degrade dramatically for unequal intensities ratio. The DPCM exhibits critical slowing down in the vicinity of the oscillation threshold. A two-dimensional coupled-modes perturbation analysis of the DPCM is introduced and its basic predictions are in a good qualitative agreement with the results of the experimental study.\n\nFinally, we analyze the nonlinear optical second harmonic generation in materials with strong photorefractivity. In the presence of strong self-phase modulation the phase matching conditions are modified and we found that in some cases this leads to a unique effect, namely, the nonlinear self-phase matching of optical nonlinear interaction. Strong photorefractive response manifests itself in two characteristic and very apparent manners; a large change in the conversion efficiency and self-defocusing of the generated second harmonic beam. We introduced a two-dimensional model of photorefractive effect and found its predictions to be in a good qualitative agreement with the observed transverse dynamics.\n", "doi": "10.7907/RYVB-3254", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:1845", "collection": "thesis", "collection_id": "1845", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05172005-084805", "primary_object_url": { "basename": "Shakouri_a_1996.pdf", "content": "final", "filesize": 3521572, "license": "other", "mime_type": "application/pdf", "url": "/1845/1/Shakouri_a_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Electron transport in quantum well infrared photodetectors", "author": [ { "family_name": "Shakouri", "given_name": "Ali", "clpid": "Shakouri-A" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In this work the technique of molecular beam epitaxy is used to grow GaAs/AlGaAs multiquantum well structures. The material composition and thicknesses are chosen in a way that the electrons in the device interact resonantly with infrared radiation. This interaction originates from quantized energy states (subbands) in the conduction band of the material. The infrared absorption and photocurrent spectroscopies, in conjunction with standard DC-characterizations, are used to investigate electron transport in these structures.\n\nAfter a brief description of electronic energy states based on the multi-band k.p approximation, the optical properties of intersubband transitions are theoretically and experimentally investigated. Evidence for the above-the-barrier energy states (continuum minibands) affecting the absorption and photocurrent spectra is presented.\n\nStudying electron transport perpendicular to the multiquantum well layers, different regimes of miniband and hopping conduction are distinguished. It is shown that sequential resonant tunneling and electric field domain formation occur even in very weekly coupled quantum wells (separated by 44 nm barriers), its application to the design of voltage-controlled multi-color infrared detectors is discussed and demonstrated. Finally, the low bias behavior of quantum well detectors is analyzed and evidence for photocurrent flowing in the opposite direction to the applied bias is presented.", "doi": "10.7907/aqq2-yj56", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:2049", "collection": "thesis", "collection_id": "2049", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05252005-084438", "primary_object_url": { "basename": "OBrien_jd_1996.pdf", "content": "final", "filesize": 8158512, "license": "other", "mime_type": "application/pdf", "url": "/2049/1/OBrien_jd_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Design, growth, and characterization of vertical cavity surface emitting lasers", "author": [ { "family_name": "O'Brien", "given_name": "John David", "clpid": "O'Brien-J-D" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Vertical cavity surface emitting laser design, growth, and characterization is discussed. Theoretical models for gain in semiconductors as well as for the threshold gain in vertical cavity lasers is presented. The distributed Bragg mirrors used in these lasers are treated theoretically using the coupled-mode approach and with a matrix method that is generalized to include gain and loss.\r\n\r\nThe growth by molecular beam epitaxy of these structures is also discussed including steps taken to obtain precise, reproducible growth rates. Specific problems and tradeoffs encountered in the growth include greater oxygen incorporation at the lower substrate temperatures needed to ensure precise thickness control. Beryllium diffusion is also discussed and SIMS measurements are presented.\r\n\r\nTwo types of vertical cavity lasers are demonstrated. The first is a hybrid semiconductor/dielectric structure. In this design, the n-doped mirror and the optical cavity are epitaxially grown semiconductors and the top mirror is a SiO2/Si3/N4 distributed Bragg reflector added to the structure by reactive sputter deposition. These lasers have InGaAs quantum wells and are top-emitting near 980 nm. This design has the advantage of removing the top mirrors from the current path which reduces the series resistance. Threshold voltages of 1.8-1.9 V were obtained from 18 \u00b5m diameter lasers. In addition, the hybrid structure allows characterization before the deposition of the top mirror. Measurements of the carrier distribution and the temperature of the devices operating without the top mirrors are presented. A minimum lasers threshold current of 2.5 mA was obtained from a 6 \u00b5m diameter laser, and a maximum peak power of 1.67 mW was obtained from a 12 \u00b5m diameter laser. The lasers exhibit strongly index-guided transverse modes and are multi-moded above threshold.", "doi": "10.7907/79nd-7w93", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:4180", "collection": "thesis", "collection_id": "4180", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10192007-092215", "primary_object_url": { "basename": "Regehr_mw_1995.pdf", "content": "final", "filesize": 4484119, "license": "other", "mime_type": "application/pdf", "url": "/4180/1/Regehr_mw_1995.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Signal extraction and control for an interferometric gravitational wave detector", "author": [ { "family_name": "Regehr", "given_name": "Martin W.", "clpid": "Regehr-M-W" } ], "thesis_advisor": [ { "family_name": "Drever", "given_name": "Ronald W. P.", "clpid": "Drever-R-W-P" }, { "family_name": "Raab", "given_name": "Frederick J.", "clpid": "Raab-F-J" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Large interferometers are currently under construction for the detection of gravitational radiation. These will contain a number of optical surfaces at each of which the relative phase of incident beams must be kept strictly controlled in order to achieve high sensitivity.\n\nThe type of interferometer considered here consists of two Fabry-Perot cavities illuminated by a laser beam which is split in half by a beam splitter, together with a recycling mirror between the laser and the beam splitter, which reflects light returning from the beam splitter toward the laser back into the interferometer. A scheme for sensing deviations from proper interference has been analyzed and the adequacy of this method for incorporation in a control system has been evaluated. The sensing scheme involves phase modulating the laser light incident on the interferometer, introducing an asymmetry in the distances between the Fabry-Perot cavities and the beam splitter, and demodulating the signals from photodetectors monitoring three optical outputs of the interferometer. These optical outputs are light returning to the laser, light extracted by a pick-off from between the recycling mirror and the beam splitter, and light leaving the interferometer at the beam splitter.\n\nThe analysis has shown that the matrix of transfer functions from mirror displacement to demodulated signal is ill-conditioned, that as many as three of the transfer functions may contain right half plane zeros, and that one of these transfer functions can be affected by the modulation depth. The performance of the closed-loop system, however, need not be significantly affected, provided that certain constraints are observed in the optical and electronic design.\n\nA table-top interferometer has been constructed, to demonstrate the feasibility of constructing a control system using this sensing scheme and to compare the response of the interferometer with that predicted by calculations. Good agreement between the experiment and the calculation has been obtained.\n", "doi": "10.7907/5EYV-5813", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:3642", "collection": "thesis", "collection_id": "3642", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09192007-110145", "primary_object_url": { "basename": "Almogy_g_1995.pdf", "content": "final", "filesize": 9047173, "license": "other", "mime_type": "application/pdf", "url": "/3642/1/Almogy_g_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Quantum Well Intersubband Transitions: Nonlinear Optics, Refractive Index and Infrared Modulation", "author": [ { "family_name": "Almogy", "given_name": "Gilad", "clpid": "Almogy-Gilad" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The nonperturbative theory for the nonlinear optical interaction of quantum well intersubband transitions is developed. The nonlinear optical response of intersubband transitions in quantum wells is rigorously derived and the implications of their resonantly-enhanced nature are examined. Limitations on the use of the standard expansion of the induced polarization in terms of perturbative nonlinear coefficients are presented and it is shown that an alternative nonperturbative formalism is necessary for analyzing intersubband device applications. Upper limits are derived on the magnitudes of several key intersubband transition-induced nonlinear processes. It is shown that for both electrooptic and all-optic modulation, resonantly-enhanced absorption modulation is inherently preferable to phase modulation. A limit on the second-harmonic intensity that may be generated in a given propagation length and modified design criteria for optimizing second-harmonic generation in quantum wells are also obtained from the nonperturbative formalism.
\r\n\r\nThe large and highly dispersive refractive index contribution of intersubband transitions was observed for the first time through the birefringence induced in a GaAs/AlGaAs multi-quantum well stack. It is shown that this index, rather than the absorption induced by intersubband transitions, may become the dominant limitation on frequency conversion efficiencies. Potential applications of this controllable refractive index for a novel phase-matching technique of second-harmonic generation and for improved waveguiding in semiconductors is suggested and analyzed.
\r\n\r\nRemoval of charge integration limitations upon the performance of thermal imagers through the 'ac'-coupling of infrared focal-plane arrays is suggested. This is achieved by the monolithic integration of an intersubband infrared absorption modulator and detector leading to a modulation depth of 45% at a wavelength of 10.6\u00b5m. The uniquely accurate design of the coupled quantum well infrared modulator was based on a self-consistent computer model of the Schrodinger and Poisson equations in quantum wells, taking into account many body effects, band nonparabolicity and flat band boundary conditions. Monolithic integration of the modulator and detector also turns out to be a simple and accurate method of studying the optical properties of quantum wells under bias. This technique led to the first observation of the exchange-interaction's contribution to the charge transfer between coupled quantum wells.
", "doi": "10.7907/3qj9-9777", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4099", "collection": "thesis", "collection_id": "4099", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10152007-130350", "primary_object_url": { "basename": "Kewitsch_as_1995.pdf", "content": "final", "filesize": 8189527, "license": "other", "mime_type": "application/pdf", "url": "/4099/1/Kewitsch_as_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Part I. Optically induced, ferroelectric domain gratings in photorefractive crystals and applications to nonlinear optics. Part II. Self-focusing and self-trapping of optical beams upon photopolymerization and applications to microfabrication", "author": [ { "family_name": "Kewitsch", "given_name": "Anthony S.", "clpid": "Kewitsch-A-S" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Cross", "given_name": "Eric", "clpid": "Cross-E" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Grubbs", "given_name": "Robert H.", "clpid": "Grubbs-R-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis explores the application of two distinct nonlinear optical phenomena, the \nphotorefractive effect and photopolymerization, to optically generate microstructures \nwith feature sizes on the order of optical wavelengths. First, we have found that in \ncertain photorefractive crystals, the photogenerated space charge field dynamically aligns \nferroelectric domains. This is demonstrated by the observation of Barkhausen noise \nlinked to the formation of domain gratings. Domain gratings are recorded with spatial \nperiods on the order of optical wavelengths, which we use for quasi-phase matched \nsecond harmonic generation and holographic data storage.\n\nThe second part of this thesis explores the nonlinear optical response accompanying \nphotopolymerization. In some photopolymers, the crosslinking of polymer chains \ninduces a significant increase in the index of refraction in the exposed region. This index \nperturbation acts as a lens which subsequently focuses down the input light wave. We \nobserve self-focused and self-trapped optical beams upon photo-induced crosslinking of a \nliquid monomer. In the case of self-trapping, the inherent diffraction of the optical beam \nis exactly balanced by self-focusing, so the diameter of the beam does not change as it \npropagates through the medium. Most importantly, this waveguiding generates solid \npolymer microstructures in the illuminated region, which can be used to fabricate micro-electromechanical systems and optical interconnects.\n", "doi": "10.7907/ngzk-1s10", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4115", "collection": "thesis", "collection_id": "4115", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10162007-131138", "primary_object_url": { "basename": "Kitching_je_1995.pdf", "content": "final", "filesize": 6257080, "license": "other", "mime_type": "application/pdf", "url": "/4115/1/Kitching_je_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Quantum noise reduction in semiconductor lasers using dispersive optical feedback", "author": [ { "family_name": "Kitching", "given_name": "John E.", "clpid": "Kitching-J-E" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes the phase and amplitude noise properties of semiconductor lasers subjected to weak, dispersive optical feedback. In the first half, experiments demonstrating reductions in the laser frequency noise power spectrum and spectral linewidth by several orders of magnitude are presented. Weak optical feedback is applied to the laser by an external cavity containing an atomic vapor. The presence of the vapor adds to the dispersion of the cavity and simultaneously locks the laser to a fixed frequency reference. The role of 1/f frequency noise in limiting the effectiveness of this linewidth reduction technique is investigated and 1/f noise is found to be the dominant contribution to the linewidth under strong optical feedback conditions.\r\n\r\nAn electronic feedback scheme utilizing FM sideband locking is then implemented alongside the optical feedback, and an additional reduction in the low frequency 1/f frequency noise power spectrum by over two orders of magnitude is obtained. With both systems operating simultaneously, the spectral linewidth is narrowed from its free-running value of about 20 MHz to 1.4 kHz. Excellent absolute frequency stability is also achieved.\r\n\r\nIn the second half, the effects of optical feedback on the quantum mechanical amplitude noise properties of the laser are examined. A fully quantum mechanical theory of amplitude and phase noise for a semiconductor laser with weak optical feedback is developed, and the nature and limits of the noise reduction using this technique are established. Particular attention is given to the feedback-induced enhancement of the amplitude squeezing which can be obtained in a pump-suppressed semiconductor laser: an improvement in the squeezing by 3 dB is predicted under moderate pumping. Somewhat larger noise reductions are expected when the laser is operating closer to threshold. Measurements performed on a laser biased close to threshold are then described and a reduction in the low frequency amplitude noise power spectrum by 7 dB is obtained.\r\n\r\nAn experimental investigation of the effects of optical feedback on the amplitude squeezing in a semiconductor laser is then discussed. The low frequency squeezing in a room temperature device is increased from 3% below the standard quantum limit (SQL) under free-running conditions to 19% below the SQL with optimal feedback. The experimental results are found to agree poorly with the single-mode model and a multi-mode model including the effects of asymmetrical cross-mode non-linear gain is developed to explain the discrepancy. Finally, further experimental investigation into the generation of amplitude squeezed light is presented using a commercial laser with no intentional external modifications. Squeezing as large as 29% below the SQL is measured using a balanced homodyne detector with the laser operating near room temperature, corresponding to 41% below the SQL at the output facet of the laser.\r\n", "doi": "10.7907/ANGH-BY42", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4364", "collection": "thesis", "collection_id": "4364", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11012007-104414", "primary_object_url": { "basename": "Iannelli_jm_1995.pdf", "content": "final", "filesize": 21094400, "license": "other", "mime_type": "application/pdf", "url": "/4364/1/Iannelli_jm_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Coherence and spectral properties of composite-cavity semiconductor lasers", "author": [ { "family_name": "Iannelli", "given_name": "John M.", "clpid": "Iannelli-J-M" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis addresses many current issues in the theoretical and experimental aspects of coherence and spectral properties of semiconductor lasers. It begins with a brief overview of the theory of fluctuations in semiconductor lasers. This includes a study of relative intensity noise, frequency/phase noise, and frequency chirp. A method of spectral linewidth reduction and stabilization is then proposed and analyzed. This method utilizes an atomic resonance in cesium to which a semiconductor laser can be frequency locked. A Van der Pol analysis as well as a rate equation analysis are carried out and predict reductions in the spectral linewidth, frequency chirp, and enhanced frequency stability. Experimental results confirm several aspects of the theory and also introduce the effects of 1/f noise in semiconductor lasers. Spectral linewidth reductions by a factor of 2000 below the solitary laser linewidth are presented.\n\nInvestigations are then made into the spectral characteristics of multielectrode distributed feedback (DFB) lasers. A novel measurement technique is introduced which utilizes the phase angle between the FM and AM responses for the determination of adiabatic chirp and linewidth enhancement factors. The mode switching properties of these devices are then studied within the context of bistable operation. Bistability in output power and output wavelength is shown and is applied to experiments in stochastic resonance. Using bistable DFB and Fabry-Perot semiconductor lasers, stochastic resonance is demonstrated experimentally in different laser systems as well as in electronic circuits. The effect is analyzed from a rate equation approach as well as a Kramer's escape approach. Results predict a noise suppression at higher even harmonic frequencies which are then experimentally verified.\n", "doi": "10.7907/y55j-f079", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4145", "collection": "thesis", "collection_id": "4145", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10172007-153538", "primary_object_url": { "basename": "Pedroni_va_1995.pdf", "content": "final", "filesize": 4776803, "license": "other", "mime_type": "application/pdf", "url": "/4145/1/Pedroni_va_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "VLSI Systems for Analog and Hamming Parallel Computation", "author": [ { "family_name": "Pedroni", "given_name": "Volnei Antonio", "clpid": "Pedroni-Volnei-Antonio" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Middlebrook", "given_name": "Robert David", "clpid": "Middlebrook-R-D" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis explores the vast field of physically implementing parallel-computing algorithms. In this research, we introduce a series of new circuit architectures and new technology applications, which implement multi-dimensional functions that are at the heart of many parallel signal processing systems, e.g., neural and Hamming networks, vector quantizers, and median filters. The functions are realized using low-cost, low-power, high-density technologies (CMOS and CCD), fully compatible with current industrial processes. The systems are either analog or hybrid, allowing lower time and/or storage complexities in many types of applications when compared to fully digital systems. Special emphasis is placed on circuit modeling, with the purpose of thoroughly understanding the potentialities - and limitations - of each alternative. The models are verified experimentally on most occasions. As a consequence, the results presented in this dissertation are expected not only to provide new technological alternatives, but also new means of evaluating the technologies themselves.
\r\n\r\nChapter 1 presents an introductory discussion on parallel systems. It has three main purposes. One is to describe some of the parallel functions whose implementations we are interested in. Another is to present a graphical discussion on how certain multidimensional systems work, which is probably the best way of describing - and appreciating - systems of this kind. And finally to describe basic guidelines concerning this research.
\r\n\r\nChapter 2 discusses a function that is inherent to most analog parallel processors, the winner-take-all function. The reason for it to be developed first is that this function is part of many other function realizations. A global discussion is presented, which provides an overview on the potentialities of most implementations available in CMOS technology, followed by high-resolution alternatives. The use of this function to implement other functions and systems is also illustrated.
\r\n\r\nChapter 3 presents a detailed discussion on charge-coupled device (CCD) technology and its applications to parallel signal processing systems. This technology, compatible with conventional double-poly CMOS, is of interest due to its low power consumption and very high integration density, allowing the construction of very efficient vector-matrix multipliers and Hamming networks. To overcome its main limitation (i.e., charge-transfer inefficiency), a locally-controlled architecture is introduced. Several chips and extensive measurements are shown, with the purpose of concretely evaluating the performance of this technology when performing signal processing tasks.
\r\n\r\nFinally, Chapter 4 describes further research on CMOS cells that compute distance-based functions. These circuits allow the construction of LMS and other distance-based parallel processors, and provide additional valuable means of further examining the use of MOS technology for analog computation. Once again experimental results are presented, and the systems are illustrated through vector quantizers, Hamming networks, vector multipliers, and median filters. This chapter also provides further applications of the winner-take-all function to the construction of more complex functions.
", "doi": "10.7907/DC5Z-3Q89", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4173", "collection": "thesis", "collection_id": "4173", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10192005-081338", "primary_object_url": { "basename": "Cauwenberghs_g_1994.pdf", "content": "final", "filesize": 9303514, "license": "other", "mime_type": "application/pdf", "url": "/4173/1/Cauwenberghs_g_1994.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Analog VLSI Autonomous Systems for Learning and Optimization", "author": [ { "family_name": "Cauwenberghs", "given_name": "Gert", "clpid": "Cauwenberghs-Gert" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Baldi", "given_name": "Pierre", "clpid": "Baldi-Pierre" }, { "family_name": "Barr", "given_name": "Alan H.", "clpid": "Barr-A-H" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The integration of adaptive functions within analog neural hardware, while certainly promising to enhance system performance, has for long been hindered by technological difficulties due to the complexity and sensitivity of standard adaptive algorithms. We present a general framework for self-contained adaptation in analog VLSI supporting a broad class of supervised learning and optimization tasks, which largely alleviates the implementation problems by virtue of a robust system approach exploiting statistics and redundancy in stochastic processes. Specifically, the framework includes: i) a perturbative algorithm based on stochastic approximation to optimize a set of parameters in an arbitrary deterministic system, these parameters being adjusted according to global performance evaluations rather than using explicit knowledge about the internal structure of the system; and ii) a scalable and modular CMOS architecture that implements this algorithm, and that additionally provides for embedded long-term dynamic storage of the volatile analog parameter values, quantized locally and refreshed autonomously on capacitors with direct external access in both digital and analog formats. We analyze the convergence and scaling properties of the stochastic algorithm, present on-line versions of the algorithm for supervised learning in dynamical systems, and provide experimental results demonstrating real-time trajectory learning on an analog CMOS chip containing a network of six fully recurrent dynamical neurons. We also include results demonstrating robust long-term retention of locally stored volatile information in analog VLSI using the autonomous refresh technique.", "doi": "10.7907/CW78-8H63", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:7619", "collection": "thesis", "collection_id": "7619", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04192013-141541657", "primary_object_url": { "basename": "Schrans_T_1994.pdf", "content": "final", "filesize": 26386342, "license": "other", "mime_type": "application/pdf", "url": "/7619/1/Schrans_T_1994.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Part 1: Longitudinal static and dynamic effects in semiconductor lasers. Part II: Spectral characteristics of passively mode-locked quantum well lasers", "author": [ { "family_name": "Schrans", "given_name": "Thomas", "clpid": "Schrans-T" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In the first part of this thesis a study of the effect of the longitudinal distribution of optical intensity and electron density on the static and dynamic behavior of semiconductor lasers is performed. A static model for above threshold operation of a single mode laser, consisting of multiple active and passive sections, is developed by calculating the longitudinal optical intensity distribution and electron density distribution in a self-consistent manner. Feedback from an index and gain Bragg grating is included, as well as feedback from discrete reflections at interfaces and facets. Longitudinal spatial holeburning is analyzed by including the dependence of the gain and the refractive index on the electron density. The mechanisms of spatial holeburning in quarter wave shifted DFB lasers are analyzed. A new laser structure with a uniform optical intensity distribution is introduced and an implementation is simulated, resulting in a large reduction of the longitudinal spatial holeburning effect.
\r\n\r\nA dynamic small-signal model is then developed by including the optical intensity and electron density distribution, as well as the dependence of the grating coupling coefficients on the electron density. Expressions are derived for the intensity and frequency noise spectrum, the spontaneous emission rate into the lasing mode, the linewidth enhancement factor, and the AM and FM modulation response. Different chirp components are identified in the FM response, and a new adiabatic chirp component is discovered. This new adiabatic chirp component is caused by the nonuniform longitudinal distributions, and is found to dominate at low frequencies. Distributed feedback lasers with partial gain coupling are analyzed, and it is shown how the dependence of the grating coupling coefficients on the electron density can result in an enhancement of the differential gain with an associated enhancement in modulation bandwidth and a reduction in chirp.
\r\n\r\nIn the second part, spectral characteristics of passively mode-locked two-section multiple quantum well laser coupled to an external cavity are studied. Broad-band wavelength tuning using an external grating is demonstrated for the first time in passively mode-locked semiconductor lasers. A record tuning range of 26 nm is measured, with pulse widths of typically a few picosecond and time-bandwidth products of more than 10 times the transform limit. It is then demonstrated that these large time-bandwidth products are due to a strong linear upchirp, by performing pulse compression by a factor of 15 to a record pulse widths as low 320 fs.
\r\n\r\nA model for pulse propagation through a saturable medium with self-phase-modulation, due to the a-parameter, is developed for quantum well material, including the frequency dependence of the gain medium. This model is used to simulate two-section devices coupled to an external cavity. When no self-phase-modulation is present, it is found that the pulses are asymmetric with a sharper rising edge, that the pulse tails have an exponential behavior, and that the transform limit is 0.3. Inclusion of self-phase-modulation results in a linear upchirp imprinted on the pulse after each round-trip. This linear upchirp is due to a combination of self-phase-modulation in a gain section and absorption of the leading edge of the pulse in the saturable absorber.
\r\n", "doi": "10.7907/6fvd-ez10", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:4948", "collection": "thesis", "collection_id": "4948", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12112007-133429", "primary_object_url": { "basename": "Zhao_b_1994.pdf", "content": "final", "filesize": 4541457, "license": "other", "mime_type": "application/pdf", "url": "/4948/1/Zhao_b_1994.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Threshold and Dynamics in Semiconductor Quantum Well Lasers", "author": [ { "family_name": "Zhao", "given_name": "Bin", "clpid": "Zhao-Bin" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The application of semiconductor lasers to optical communications and interconnects requires low threshold current, high-frequency modulation, and low-noise characteristics. Quantum well (QW) lasers have received considerable attention due to the demonstrated low threshold current, predicted superior modulation and spectral dynamics due to the reduction of active layer thickness and corresponding modification of density of states for the injected carriers in the extremely thin active region. However, in comparison with their bulk counterparts - double heterostructure (DH) lasers, quantum well lasers have not experimentally demonstrated significant improvement in the modulation bandwidth especially in the case of single quantum well (SQW) lasers.
\r\n\r\nIn a practical quantum well structure, the separate confinement heterostructure (SCH) is usually used to confine the optical field in the waveguide and the injected carriers in the quantum well region. The fundamental Fermi-Dirac statistics results in that, in addition to the carrier population in the quantum well region, there is also a significant carrier population in the optical confining region. In the previous differential gain evaluations, the carrier population in the energy states in the optical confining region of the separate confinement heterostructure (referred as the state/band filling effects in QW lasers) was omitted.
\r\n\r\nThe state filling effects are, in principle, inherent in any QW structure due to the Fermi distribution of the injected carriers. A re-evaluation of differential gain for typical GaAs/AIGaAs QW and DH bulk lasers with consideration of state filling shows that (i) there is no differential gain enhancement in SQW lasers in comparison to the bulk lasers; (ii) there is an additional differential gain enhancement in multiple quantum well (MQW) lasers stemming from the reduction of state filling. These conclusions are consistent with the experimental results of high speed modulation bandwidth in semiconductor lasers.
\r\n\r\nThese theoretical and experimental investigations provide useful guides in design of QW lasers of ultra-high performance. Using these design criteria, strained InGaAs MQW buried heterostructure (DH) lasers have been fabricated. These lasers have demonstrated record low lasing threshold currents (0.25 mA) and high speed at low operation current (3dB bandwidth of 5 GHz at 2.1 mA). These lasers are potentially important for optical interconnects and local area network communication systems.
", "doi": "10.7907/5ZK1-TC36", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:3240", "collection": "thesis", "collection_id": "3240", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08272007-091655", "primary_object_url": { "basename": "Eng_le_1993.pdf", "content": "final", "filesize": 8319328, "license": "other", "mime_type": "application/pdf", "url": "/3240/1/Eng_le_1993.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Low threshold current strained InGaAs/AlGaAs quantum well lasers", "author": [ { "family_name": "Eng", "given_name": "Lars E.", "clpid": "Eng-L-E" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\nStrained InGaAs quantum well lasers offer the prospect of lower threshold currents, higher modulation speed, and lower linewidths than lattice matched GaAs quantum well lasers. In addition, the useful wavelength region of the GaAs material system is extended from 0.87[...] to beyond 1[...] with the addition of indium to the quantum well.\n\nThe lasers are fabricated using Molecular Beam Epitaxy (MBE) for the semiconductor layer structure. Liquid Phase Epitaxy (LPE) is then used to provide lateral optical mode and current confinement. Broad area threshold current densities of [...] is the first demonstration of high quality MBE grown strained InGaAs laser material. Measured transparency currents of 25[...] are a factor of two lower than in GaAs, which is consistent with a lower valence band density of states in the strained material. Buried heterostructure lasers made from this material with 2[...] wide stripe widths lase with a minimum threshold of 1.0mA (CW), the lowest value for a single quantum well laser with as-cleaved mirrors in any material system. With high reflectivity coatings (R=0.9) the first sub milliampere strained InGaAS lasers are obtained, with [...]. Details of the material growth, device fabrication, and device optimization are presented.\n\nThe broad gain bandwidth of single quantum well lasers is used to tune the lasing wavelength of optimized GaAs lasers over 125 nm and InGaAs lasers over 170 nm in an external cavity configuration. The measured tuning curves obtained for the InGaAs lasers are qualitatively different, and the difference can be attributed to the modified strained valence band strucure.\n\nLow temperature (5\u00b0K) performance of low threshold lasers is investigated. The decrease in threshold with temperature is found to be linear over a range of 200\u00b0K for both GaAs and InGaAs with a larger decrease in threshold for the GaAs case. This result agrees well with a lowered valence band effective mass in the strained laser.", "doi": "10.7907/wxtc-4x91", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:3243", "collection": "thesis", "collection_id": "3243", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08272007-111424", "primary_object_url": { "basename": "Grave_i_1993.pdf", "content": "final", "filesize": 6112485, "license": "other", "mime_type": "application/pdf", "url": "/3243/1/Grave_i_1993.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "GaAs quantum well devices for detection and nonlinear optics in the mid-infrared", "author": [ { "family_name": "Grave", "given_name": "Ilan", "clpid": "Grave-I" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The basic physical limits for infrared detection based on intersubband processes in semiconductor quantum wells are presented. An evaluation of the potential of GaAs intersubband detectors and a comparison with other systems is attempted. It is shown that the performances of the single GaAs detector falls short with respect to the single HgCdTe detector. Still, the performances of GaAs intersubband detectors answer the needs of many conceivable applications; this fact, together with the maturity, integrability and uniformity of the cheaper GaAs technology might make these detectors the choice for many future applications and systems.\n\nOptimization of parameters in the design and epitaxial growth of these structures yield standard intersubband detectors with very respectable performances at reasonable cooling costs.\n\nThe narrow bandwidth and the lack of post-growth tunability limit the capability and versatility of intersubband detection. A new kind of intersubband detector, the multistack integrated detector, is conceived in an attempt to address these issues. This detector can operate in a number of modes; it can have a narrow or wide bandwidth of detection, and even a voltage-controlled expandable bandwidth. Among its features a multi-color option and a switching-peak option for combined or alternate color detection. The underlying physics involves the formation, expansion and readjustment of electric field high and low domains along the multi-quantum well region.\n\nAdditional topics in the physics and applications of intersubband processes for detection of infrared light are explored: a band-gap design involving a variably-spaced superlattice barrier, is investigated by photocurrent spectroscopy. The experiments reveal the subtle breaking of the parity selection rules, and also the possibility of detecting infrared light at shorter wavelengths than previously thought possible in the GaAs/AlGaAs system.\n\nThe second part of this thesis deals with the study and observation of enhanced nonlinear optical effects at the mid infrared, close to intersubband resonances. Second harmonic generation is obtained around 5 \u00b5m. Third-order effects are then investigated in different experimental configurations, including the first observation of phase conjugation based on these nonlinearities. Very large third-order susceptibilities and intensity-dependent refractive indices are deduced from the experimental results.", "doi": "10.7907/mjwc-4k88", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:3303", "collection": "thesis", "collection_id": "3303", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08312007-094832", "primary_object_url": { "basename": "Neugebauer_cf_1993.pdf", "content": "final", "filesize": 4822520, "license": "other", "mime_type": "application/pdf", "url": "/3303/1/Neugebauer_cf_1993.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Parallel Analog Computation with Charge Coupled Devices", "author": [ { "family_name": "Neugebauer", "given_name": "Charles F.", "clpid": "Neugebauer-Charles-F" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Many signal processing and neural network algorithms can be mathematically described in terms of vector matrix multiplication. This thesis introduces two new architectures for computing high-speed vector matrix multiplication using charge coupled devices. These integrated circuits have been designed to accept optical matrix input as well as direct electrical matrix input. In both architectures, the matrix elements are stored as analog charge packets in CCD wells while the vectors are communicated to and from the integrated circuits by electrical means.\r\n\r\nThe first architecture accomplishes the vector matrix product using a semiparallel computation scheme that requires N clock cycles of the device to complete one vector matrix multiplication where N is the length of the input vector. An analysis of the linearity and charge transfer induced errors is given. The circuit represents an advance over other analog signal processors in density and speed but has serious shortcomings in accuracy, particularly the limited precision of the input vectors.\r\n\r\nThe second architecture is based on charge injection device (CID) imager arrays and addresses many of the inadequacies of the semiparallel architecture. A fully parallel circuit, the CID has similar density and much higher computation speed and accuracy. A novel digital input method is introduced that extends the input vector precision significantly. In addition, accuracy issues related to charge transfer efficiency are resolved. An analysis of linearity and accuracy is provided showing the advantages of the architecture over previous implementations.", "doi": "10.7907/3e7h-9p50", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:3246", "collection": "thesis", "collection_id": "3246", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08272007-134313", "primary_object_url": { "basename": "Hofmeister_rj_1993.pdf", "content": "final", "filesize": 11162985, "license": "other", "mime_type": "application/pdf", "url": "/3246/1/Hofmeister_rj_1993.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Growth and applications of photorefractive potassium lithium tantalate niobate (KLTN)", "author": [ { "family_name": "Hofmeister", "given_name": "Rudolf", "clpid": "Hofmeister-R" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\nThis thesis describes the growth of photorefractive potassium lithium tantalate niobate (KLTN) single crystal material and characterization of its physical and photorefractive properties. The band transport model is used to discuss the conventional photorefractive effect. The coupled mode formalism is introduced to determine the interaction of interfering light beams in a photorefractive material. Solutions for intensity coupling and phase coupling between two beams, as well as diffraction off a dynamic index grating, are presented for both the copropagating and counterpropagating experimental geometries. These solutions are obtained for arbitrary photorefractive phase, [...]. The linear- and quadratic electro-optic effects are discussed. The influence of electric field application on the electro-optic tensor is described.\n\nThe top seeded solution growth method is reviewed. The design and construction of a crystal growth system is described. The growth procedures of KLTN are enumerated for several compositions and dopant types. Phase diagrams of the KLTN system are determined. Structural properties of the grown crystals are presented. Certain material characteristics of KLTN are discussed. These include the phase transition temperatures, dielectric properties, and the optical absorption properties.\n\nElectric field control of the photorefractive effect, beam coupling and diffraction, is demonstrated for paraelectric KLTN. A theory is developed to describe the diffraction of beams off photorefractive index gratings in paraelectric KLTN. The solutions of the coupled mode equations are used to develop methods of determining the photorefractive phase [...] in a photorefractive material. These methods are experimentally demonstrated for several types of photorefractive material. In addition, they are used to corroborate a theory describing the magnitude and phase of the net holographic grating in paraelectric KLTN under applied electric field.\n\nA new effect, the Zero External Field Photorefractive (ZEFPR) effect is studied, as well as the application of its unique zero phase ([...] = 0) photorefractive gratings. The ZEFPR effect is forbidden by the conventional photorefractive theory; its origin is shown to be due to the creation of strain gratings under spatially periodic illumination. A theory of coordination of microscopic strains by a macroscopic (growth induced) strain is presented. The ZEFPR gratings are shown to possess identically zero phase when no external electric field is applied. This property is employed in the implementation of various new linear phase-to-intensity transduction devices. In particular, an all-optical phase modulation/vibration sensor (microphone) is described. This device is expected to have numerous applications in environments where electric fields cannot be permitted. The possible implementation of ZEFPR gratings in high speed self aligning interferometric data links is discussed, as well as implementation of a novel self aligning holographic image subtraction device.\n\nThe final chapter is devoted to the solution of beam coupling and diffraction off of a \"fixed\" photorefractively written holographic plane grating. The solutions and mathematical tools developed in this chapter are used extensively throughout the thesis: in chapters two and five to describe diffraction off a photorefractive grating, in chapters seven and eight to solve for the beam coupling off a grating when one beam is phase modulated, and in chapter nine to study the spectral response of fixed holographic interference filters. The techniques are presented with sufficient generality to allow application to numerous other problems, not limited to the ones described here.\n", "doi": "10.7907/zm1c-8w92", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:6675", "collection": "thesis", "collection_id": "6675", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09152011-113656037", "primary_object_url": { "basename": "Wu_s-w_1992.pdf", "content": "final", "filesize": 22743705, "license": "other", "mime_type": "application/pdf", "url": "/6675/1/Wu_s-w_1992.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Semiconductor laser noise and linewidth reduction and Rayleigh scattering in optical fibers", "author": [ { "family_name": "Wu", "given_name": "Shu-Wu", "clpid": "Wu-Shu-Wu" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis is a theoretical and experimental investigation of monolithic linewidth reduction in multiple section distributed-feedback (DFB) lasers and of phase-to-intensity conversion noise due to Rayleigh scattering in optical fiber links. In the first part, the physics of semiconductor laser dynamics and noise is reviewed. A Van der Pol noise analysis of laser amplitude and phase fluctuations is conducted. Linewidth reduction in lasers with intra-cavity dispersive medium is analyzed. The semiconductor laser subjected to an external optical feedback is studied by treating the feedback as a part of facet complex reflectivity.
\r\n\r\nIn the second part, a theoretical study of three section semiconductor DFB lasers is presented. The result shows that under proper pumping and biasing conditions one section lases while the other provide the necessary dispersive optical feedback for noise suppression and, hence, linewidth reduction. The benefits of having such optical feedback on modulation responses is also demonstrated.
\r\n\r\nAn experimental study of three section semiconductor DFB lasers is presented in the third part. Processing and standard testing procedures of the multiple section DFB laser is described. Subsequently the scanning Fabry-Perot, optical spectrum analyzer, and the delayed-self-heterodyne method are used for the measurements. The experimental results demonstrate a moderate reduction in laser linewidth.
\r\n\r\nIn the fourth part, a complete statistical theory, including the effect of random fiber index inhomogeneities, of conversion of fundamental phase fluctuation at semiconductor laser output to intensity noise in long haul optical fiber links due to Rayleigh scattering is developed. Three generic cases are considered.
\r\n\r\nIn part five, a detailed experimental study of Rayleigh induced intensity fluctuations is presented. Comparison between the theoretically predicted and experimentally measured values shows very good agreement.
\r\n\r\nThe impact of Rayleigh scattering on fiber links with periodic optical amplification is considered. The result shows linear accumulation of intensity noise due to Rayleigh scattering. To prevent a quadratic accumulation of the Rayleigh scattering induced intensity noise, optical isolators in very long haul fiber links are required. A reduction scheme of phase-to-intensity conversion noise by phase modulation is subsequently\r\nstudied.
\r\n\r\n\r\n", "doi": "10.7907/ktgv-s236", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:3111", "collection": "thesis", "collection_id": "3111", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08132007-085419", "primary_object_url": { "basename": "Sanders_s_1992.pdf", "content": "final", "filesize": 4222559, "license": "other", "mime_type": "application/pdf", "url": "/3111/1/Sanders_s_1992.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Passive mode-locking and millimeter-wave modulation of quantum well lasers", "author": [ { "family_name": "Sanders", "given_name": "Steven", "clpid": "Sanders-S" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Quantum well lasers with their optical cavities electrically divided into regions of saturable absorption and gain are passively mode-locked to generate picosecond pulse trains. Current is injected into the gain region, and the absorber is biased below the p-n junction turn-on voltage to control the absorption level and the rate of extraction of photogenerated carriers. Using only DC or low frequency electrical bias on monolithic devices, pulse trains at repetition rates above 100 GHz are generated for the first time.\n\nTheoretical considerations show that quantum well laser properties including the reduction of differential gain with increasing carrier density and the fast recovery time of the absorber allow passive mode-locking to occur at repetition rates far beyond the direct modulation bandwidth of a semiconductor laser, at frequencies above 100 GHz. The saturable absorption in the cavity, however, also induces self-sustained pulsations at a few gigahertz that can interfere with the higher frequency mode-locking process. However, it is shown that increasing the photon lifetime in the cavity can inhibit self-sustained pulsations while extending the range of conditions for high-frequency passive mode-locking.\n\nMultisection stripe lasers are fabricated from quantum well materials by etching through the highly conductive cap layer to electrically isolate regions along the stripes. A two-section monolithic triple quantum well GaAs/AlGaAs stripe laser is passively mode-locked at a 108 GHz repetition rate, with pulsewidths averaging 2.4 ps. More stable mode-locking is observed in a three-section passively mode-locked InGaAs/AlGaAs double quantum well laser emitting 5.9 ps pulses at a 42 GHz repetition rate.\n\nBy coupling a two-section quantum well buried heterostructure laser to an external cavity, the pulse train period becomes comparable to the gain and absorber recovery times and compatible with conventional optical detectors and electronics. It is shown that the laser can operate at six different harmonics of the 1.17 GHz repetition rate, by adjustment of the gain section current only. Both small and large-signal saturation models for passive mode-locking are described and applied to determine the conditions where the laser should operate at the different harmonics and are in reasonable agreement with the experimental results. From power spectrum measurements of a laser mode-locked at 546 MHz, the timing jitter is determined to be 5.5 ps above 50 Hz, and the pulse energy fluctuations less than 0.52% above 200 Hz. While it is expected that stable pulse trains can be generated at these lower repetition rates, as is demonstrated, the stability of the millimeter-wave mode-locked lasers remains a critical problem for future research.\n", "doi": "10.7907/z29s-kq29", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:4568", "collection": "thesis", "collection_id": "4568", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11152005-081932", "primary_object_url": { "basename": "Leyva_v_1991.pdf", "content": "final", "filesize": 4467367, "license": "other", "mime_type": "application/pdf", "url": "/4568/1/Leyva_v_1991.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Investigations of the photorefractive effect in potassium tantalum niobate", "author": [ { "family_name": "Leyva", "given_name": "Victor", "clpid": "Leyva-Victor" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThis thesis describes results of investigations of the photorefractive effect in potassium tantalum niobate ([...]) crystals. A band transport model is used to describe the photorefractive effect. The coupled mode equations are then introduced and used to solve self-consistently for the interaction of the light and space charge fields in a photorefractive material. The design and construction of a high temperature crystal growth system is discussed. The growth of photorefractive KTN crystals doped with a variety of transition metal dopants using the top seeded solution growth method is described. Two applications in the areas of volume holography are described which take advantage of the unique ferroelectric properties of KTN. The first makes use of the quadratic electrooptic effect in paraelectric KTN to control the magnitude of a diffracted wave with an externally applied field. Full amplitude modulation at speeds much faster than the grating formation time demonstrated. The second application described is a procedure used to fix a holographic diffraction grating in KTN. It invovles the writing of a photorefractive grating in the paraelectric phase of KTN and cooling the sample under an applied field through successive phase transitions into the rhombohedral phase.\r\n\r\nMaterials investigations of the photorefractive effect are described. Investigations focused on the optimization of the photorefractive properties of IKTN by the control of the concentration and the valence state of the photorefractive donor ions both during and after the growth stage. Absorption, photoconductivity, and electron microprobe measurements are used to identify the photorefractive species and to determine all relevant parameters which enter into the band transport model in a KTN:CuV sample after a series of thermal oxidation and reduction treatments. Holographic diffraction measurements are compared with those expected from theory. The oxidation and reduction process is modelled. Approaches to optimize the photorefractive sensitivity are discussed. The photorefractive properties of Fe and Ti doped KTN samples are investigated. Absorption and photoconductivity measurements indicate that the double dopant combination of Fe and Ti leads to an increased [...] and total Fe concentrations as compared to single doped samples. A corresponding increase in photorefractive sensitivity is measured. The dependence of the photorefractive properties of Fe and Ti doped KTN on electric field, grating period, and temperature is characterized.", "doi": "10.7907/cayt-6896", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "id": "thesis:2677", "collection": "thesis", "collection_id": "2677", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06212007-141621", "primary_object_url": { "basename": "Kan_sc_1991.pdf", "content": "final", "filesize": 2953851, "license": "other", "mime_type": "application/pdf", "url": "/2677/1/Kan_sc_1991.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Physics and applications of resonant tunneling devices", "author": [ { "family_name": "Kan", "given_name": "Sidney Chunping", "clpid": "Kan-S-C" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis addresses several important issues of the physics and applications of double barrier resonant tunneling devices on which the author worked during his graduate study at Caltech:\n\n(1) Epitaxial growth of AlAs/GaAs double barrier resonant tunneling structure on both GaAs and Si substrate (Chapter 2).\n(2) Investigation of terahertz modulation of resonant tunneling effect\n(Chapter 3).\n(3) Study of the imaginary potential in double barrier resonant tunneling (Chapter 4).\n(4) Development of the first series of optical resonant tunneling devices and parallel resonant tunneling (Chapter 5).\n\nThe history of the development of double barrier resonant tunneling and the basic theory are also discussed (Chapter 1).", "doi": "10.7907/9CXE-6C77", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "id": "thesis:700", "collection": "thesis", "collection_id": "700", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02212007-153159", "type": "thesis", "title": "GaAs/Al\u2093Ga\u2081\u208b\u2093As Quantum Well Lasers Grown on GaAs and Si by Molecular Beam Epitaxy", "author": [ { "family_name": "Chen", "given_name": "Howard ZeHua", "clpid": "Chen-Howard-ZeHua" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Molecular beam epitaxy (MBE) has been known as a \"black art\" since its invention in the early 1970's. The main goal of this thesis is to present practical techniques used daily MBE experts which have never been discussed in the literature. If this thesis can make a small step toward a better understanding and utilization of this technology, the author is more than satisfied.
\r\n\r\nThe following is a summary of experimental and theoretical work of GaAs-on-GaAs and GaAs-on-Si material growth by MBE. Except for the relatively new GaAs-on-Si research, background information is presented at a minimum level. Emphasis is made on both theoretical and experimental techniques rather than on general discussions which exist in the literature.
\r\n\r\nThe thesis begins with an introduction, in Chapter 1, to activities in molecular beam epitaxy and related crystal growth methods as well as their applications in the field of optical interconnects using low-threshold lasers and high-speed photodetectors.
\r\n\r\nIn Chapter 2, a Green's function formulation of interface matching problems is presented. A very simple equation can be derived, which can provide some support to a very controversial, yet highly successful and very popular quantum dipole model for Schottky barriers and heterojunctions by J. Tersoff. A simplified model can be obtained, which eliminates the uncertainties in Tersoff's scheme and predicts very well the band offsets for several important semiconductor heterosystems including GaAs/AlAs. The theory is found to be in excellent agreement with a photoelectric measurement on the band offsets of the GaAs/AlGaAs system.
\r\n\r\nChapter 3 deals with details of MBE growth of GaAs/AlGaAs quantum well laser material on GaAs substrates. Various growth techniques and substrate orientations are discussed. The dependence of threshold current density of a GaAs/AlGaAs GRINSCH laser on quantum well thickness is experimentally studied. The experimental results are in good agreement with a qualitative analysis. A theoretical discussion of the effect of quantum well thickness on the threshold current density is used to explain the experimental results. Furthermore, this study has achieved for the first time, threshold current densities below 100 A/cm\u00b2 in any semiconductor laser. The transparency current density obtained in this study, 60 A/cm\u00b2, is very close to the theoretical prediction of 63 A/cm\u00b2. It also establishes a record of lowest threshold current density for any semiconductor lasers.
\r\n\r\nChapter 4 presents some important issues in GaAs-on-Si research. Both the potentialities and limitations of GaAs-on-Si technology are discussed. The main advantage of GaAs-on-Si technology is the special features of Si substrates not available in GaAs substrates.
\r\n\r\nChapter 5 discusses the experimental aspects of GaAs-on-Si laser growth by MBE. The formation and prevention of antiphase domains (APDs) are discussed. Various methods to reduce defect density are presented. The first low threshold current density GaAs-on-Si laser growth by MBE, and the first room temperature continuous wave (CW) operation are described in detail. Important applications such as high-speed modulation of GaAs-on-Si stripe lasers and high-speed GaAs-on-Si p-i-n photodiodes are also presented.
\r\n\r\nAppendix I summarizes the operation and maintenance of a Riber 2300 MBE system from a practical point of view. Only several components in this MBE system are absolutely needed to grow high quality materials. It also discusses the routine material calibrations performed. Appendix II, III, IV, V, and VI deal with the details of material processing and device fabrication.
", "doi": "10.7907/thfh-4627", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:4479", "collection": "thesis", "collection_id": "4479", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11092007-090251", "primary_object_url": { "basename": "Zarem_h_1990.pdf", "content": "final", "filesize": 4079944, "license": "other", "mime_type": "application/pdf", "url": "/4479/1/Zarem_h_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Investigations of quantum wires, carrier diffusion lengths, and carrier lifetimes in GaAs/AlGaAs heterostructures", "author": [ { "family_name": "Zarem", "given_name": "Hal", "clpid": "Zarem-H" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\nNanometer scale wire structures are fabricated by selective disorder of a GaAs/AlGaAs quantum well. These structures are investigated by cathodoluminescence (CL). Spectrally resolved CL images of the structures as well as local CL spectra of the structures are resented. The effects of fabricational variations on quantum wire laser gain spectra and performance are discussed. A new technique for determining carrier diffusion lengths by cathodoluminescence measurements is presented. The technique is extremely accurate and can be applied to a variety of structures. The ambipolar diffusion length and carrier lifetime are measured in [...] for several mole fractions in the interval 0 < [...] < 0.38. These parameters are found to have significantly higher values in the higher mole fraction samples. These increases are attributed to occupation of states in the indirect valleys, and supporting calculations are presented.\n", "doi": "10.7907/ajzc-wx87", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:822", "collection": "thesis", "collection_id": "822", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03012007-144920", "primary_object_url": { "basename": "Mehuys_dg_1990.pdf", "content": "final", "filesize": 7936667, "license": "other", "mime_type": "application/pdf", "url": "/822/1/Mehuys_dg_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Linear, nonlinear, and tunable guided wave modes for high-power (GaAl)As semiconductor lasers", "author": [ { "family_name": "Mehuys", "given_name": "David Glenn", "clpid": "Mehuys-D-G" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "High-power, coherent radiation from semiconductor lasers is attractive for such diverse applications as free-space communication, optical data storage, and microsurgery. However, several factors conspire to prevent near-ideal performance from broad area devices and laser arrays. Waveguides wider than a few microns support many lateral modes with poor gain discrimination. Consequently, such modes are easily \"mixed\" by perturbations in gain and refractive index caused by gain saturation, thermal gradients, and inhomogeneities that are due to imperfect crystal growth. This causes spatially localized modes, multimode operation, and reduced spatial coherence, all of which lead to farfields broader than the \"diffraction limit.\"\n\nIn this thesis, we have investigated the influence of gain saturation on the lateral modes of broad area structures and laser arrays. Analytical and numerical techniques have been developed to solve self-consistently for mode shapes and propagation constants as a function of injected current density above threshold. For example, our analysis indicates that the gain-saturated modes of broad area lasers consist of an integer number of phase-locked \"filaments.\" In gain-guided quantum well lasers, these nonlinear modes are observed to oscillate into narrow, single-lobed farfields, which broaden only slightly with increased power output up to the 500mW level. Conversely, laser arrays have been widely touted as structures that suppress unwanted filamentation in favor of spatial mode control. Indeed, in this work we have demonstrated supermode control at the 100 mW power level by varying the diffraction region length in diffraction-coupled arrays. Both theoretically and experimentally, however, we have found the lateral modes of laser arrays to be unstable with increased current injection. Waveguides that are phase-matched below threshold become detuned under the influence of gain saturation, so that interguide power transfer is reduced. This decreases the injection-locking bandwidth, and ultimately, the spatial coherence. While undesirable for a laser oscillator, this property may be attractive for all-optical switching in nonlinear directional couplers.\n\nFinally, we have considered marrying the high-power, coherent output of broad area lasers and laser arrays with the broadband tunability possible in semiconductor lasers. In particular, the steplike density of states unique to quantum well structures results in gain spectra that are broader and flatter than comparable spectra of double heterostructure lasers. Experimentally, we have tuned uncoated, single quantum well stripe lasers in a grating-coupled external cavity over a range >125 nm centered about 800 nm. Similarly tuned broad area lasers output in excess of 200 mW (pulsed) into a single longitudinal mode over 80 nm, and buried heterostructure lasers were operated continuously over 90 nm. We expect that in the future, such devices could provide a compact, rugged, more efficient alternative to dye lasers.", "doi": "10.7907/xjjy-2330", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:1706", "collection": "thesis", "collection_id": "1706", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05092007-084117", "primary_object_url": { "basename": "Paslaski_j_1990.pdf", "content": "final", "filesize": 6480683, "license": "other", "mime_type": "application/pdf", "url": "/1706/1/Paslaski_j_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "High Speed Optoelectronics: Photodiodes, Q-Switched Laser Diode and Photoconductive Sampling", "author": [ { "family_name": "Paslaski", "given_name": "Joel Stephen", "clpid": "Paslaski-Joel-Stephen" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In this thesis, a variety of topics related to high speed optoelectronic devices and measurement techniques using ultrafast optical pulses are presented.
\r\n\r\nFollowing a brief introduction, the second chapter describes a Q-switched semi-conductor laser using a multi-quantum well active layer both for gain and as an intracavity loss modulator. While Q-Switching does not produce as short a pulse as modelocking, it does offer the advantage of adjustability of the repetition rate making it attractive as a source for digital communication links. It is also found to be preferred to the similar approach of gain switching due to less demanding requirements on the rf modulation power level and waveform. Results include a pulse width of ~ 20 ps which is fairly independent of the repetition rate, and a limiting repetition rate of 3.2 GHz. The onset of an irregular pulse train which limits the maximum modulation frequency, is analyzed by a graphical approach.
\r\n\r\nThe potential for optical interconnects has motivated a marriage between the two technologies of Si VLSI and GaAs optoelectronics. Direct integration by the growth of GaAs on Si had been impossible, but the MBE and MOCVD techniques now enable the growth of such layers and of a quality suitable for devices. The third chapter describes the operating characteristics of GaAs-on-Si lasers and photodiodes with particular attention to their high speed performance. Both the lasers and photodiodes show comparable high speed performance to similar structures fabricated on GaAs, with most of the shortcomings being in their dc characteristics.
\r\n\r\nIn the fourth chapter, a novel approach to improving the resolution of photoconductive sampling is presented, called differential sampling. This technique obviates the need for carrier lifetime reduction usually used to improve temporal resolution, and is in principal only limited by a small (few ps) RC circuit time. An analysis of the minimum detectable signal voltage shows the technique does quite well compared with lifetime reduction techniques which also tend to reduce mobility and dark resistance. An experimental demonstration of this technique is presented in chapter five. Using a two gap sampler, accurate measurement (10 ps resolution) of a 60 ps pulse response from a photodiode is achieved using photoconductors with a recovery time of only 150 ps. Performance near the fundamental Johnson noise limit is also attained, though the minimum detectable signal is higher than predicted due to low response of the photoconductors (probably due to poor contacts).
\r\n\r\nFinally, in chapter six, the possibility of retrieving an impulse response from its autocorrelation is explored. The use of the logarithmic Hilbert transform for phase retrieval has been discounted in the literature since most such work is concerned with imaging problems for which it is not appropriate due to their symmetric nature. However, causality and the decay nature of transient phenomena make this technique very suitable for use with the impulse response of passive devices. Conditions for the validity of this technique for temporal problems are presented. Simulated retrieval of two functions with similar autocorrelations is demonstrated with sufficient clarity to distinguish them, as well as showing good agreement with the original. Practical limitations and aspects -- such as noise, finite time domain, etc. -- are also simulated and discussed.
", "doi": "10.7907/dkyt-nc40", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:4444", "collection": "thesis", "collection_id": "4444", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11072006-135048", "primary_object_url": { "basename": "Sayano_k_1990.pdf", "content": "final", "filesize": 11043286, "license": "other", "mime_type": "application/pdf", "url": "/4444/1/Sayano_k_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Photorefractive properties of ferroelectric materials for optical phase conjugation, two-beam coupling, and holographic storage", "author": [ { "family_name": "Sayano", "given_name": "Koichi", "clpid": "Sayano-K" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The results of a systematic investigation of doped strontium barium niobate and potassium tantalate niobate for photorefractive beam coupling and optical holographic storage are presented in this thesis. Methods that were successfully employed to increase the magnitude of the photorefractive effect and speed up the response of these materials are also presented. Applications in the area of optical phase conjugation, distortion correction, limiting, and thresholding are also discussed.\n\nIn the first part, the equations governing the photorefractive effect through band transport are introduced. The solutions giving the internal space charge field in photorefractive materials are presented for the one carrier, one species model that approximates the process in strontium barium niobate and most other materials. The coupled equations describing the two-beam coupling effect are also derived.\n\nNext, the results of experiments using as-grown potassium tantalate niobate for holographic diffraction and strontium barium niobate for two-beam coupling are presented. With KTN, the effect of Nb concentration on the phase transition, temperature dependence of diffraction efficiency and dark storage time, and the effects of the bias electric field are discussed. With SBN, the effect of dopant type, temperature dependence of the photorefractive effect, the effects of dark conductivity in Cr-doped SBN:60, and wavelength dependence are presented.\n\nThe third part describes methods and results of increasing the magnitude of the photorefractive effect in SBN. Optimization of the grating period, oxidation and reduction heat treatments, temperature control, and applied fields are discussed. Significant increases in the two-beam coupling constant were observed in Cr-doped SBN:60 with applied fields of up to 10 kV/cm. An order of magnitude reduction of the response time in Rh-doped SBN:60 has been achieved with an applied field of 10 kV/cm.\n\nThe final part discusses applications of these materials, particularly in the areas of phase conjugation, distortion correction, and optical signal processing. A total internal reflection phase conjugate mirror using SBN instead of BaTiO3, a one-way image transmission scheme that can send a signal through a distorting medium, thresholding using a semilinear phase conjugate mirror with grating motion, and a field controlled and enhanced optical limiter are presented.\n", "doi": "10.7907/rc1x-8046", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:550", "collection": "thesis", "collection_id": "550", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02082007-092122", "type": "thesis", "title": "Dynamics, Noise Properties, and Spectral Characteristics of Semiconductor Lasers with External Coupling", "author": [ { "family_name": "Lu", "given_name": "Lun-Tseng", "clpid": "Lu-Lun-Tseng" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Breckinridge", "given_name": "James B.", "orcid": "0000-0002-9488-098X", "clpid": "Breckinridge-James-B" }, { "family_name": "Drever", "given_name": "Ronald W. P.", "clpid": "Drever-R-W-P" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is a study of the dynamics, noise properties, and linewidth of semiconductor lasers with external coupling. In Chapter 2, a general formalism is developed for obtaining the optical-field equations of semiconductor lasers with external coupling. This formalism is applied to three different types of semiconductor lasers: (1) a diode laser coupled to an external mirror, (2) an injection-locked diode laser, and (3) an axially coupled two-section diode laser. The resulting equations are the basis for the studies and discussions given in Chapters 3, 4, and 5.
\r\n\r\nThe third chapter considers, using a small-signal analysis, a single-mode semiconducor laser coupled to an external mirror. Light trapped for many round trips inside the external cavity is taken into account. Analytical expressions for the frequency and relative-intensity fluctuation spectra, the laser linewidth and the small-signal current modulation response are obtained. The fundamental mechanism that prevents the mode locking in semiconductor lasers with an external feedback is identified. The observed data on the intensity noise and the current modulation response are elucidated.
\r\n\r\nAn injection-locked semiconductor laser is studied in Chapter 4. The origin and importance of the facet's amplitude reflectivities are described. The instability occurring in the high-frequency side of the locked range is fully explored. A detailed study of the locking bandwidth is presented. It is shown that, depending on the detuning of the lasing frequency, the relative-intensity noise can be reduced or increased. It is also demonstrated on a general basis that the locked laser linewidth is the same as that of the injected field.
\r\n\r\nThe dynamics and laser linewidth of an axially coupled two-section semiconductor laser are scrutinized in the last chapter. The relative-intensity and frequency fluctuation spectra can be obtained from the results given in this chapter. A formula is obtained for the laser linewidth. This formula explains the experimental observations that the linewidth is nearly inversely proportional to the power with a nonzero intercept. Finally, the contribution to the reduction in dynamic frequency chirping of two-section lasers is clarified.
", "doi": "10.7907/frs6-t936", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:641", "collection": "thesis", "collection_id": "641", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02152007-083930", "type": "thesis", "title": "Modal Dispersal of Information and Wave Mixing in Photorefractive Crystals for Information Retrieval, Processing and Sensing", "author": [ { "family_name": "Tomita", "given_name": "Yasuo", "clpid": "Tomita-Yasuo" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Whaling", "given_name": "Ward", "clpid": "Whaling-W" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes an experimental and theoretical study on modal dispersal of information and wave mixing in photorefractive crystals for vector phase conjugation and real-time information processing. Photorefractive crystals with short drift lengths (BaTiO\u2083 and Ba\u2081\u208b\u2093Sr\u2093Nb\u2082O\u2086) and long drift ones (Bi\u2081\u2082SiO\u2082\u2080 and semi-insulating GaAs) are particularly used in this thesis.
\r\n\r\nIn the first part, the photorefractive effect in electrooptic crystals is described in terms of Kukhtarev's band transport model. The explicit solution of the space-charge electric field for the case of one photorefractive species and one type of charge carrier is extended to the case of two photorefractive species and two types of charge carriers. The enhancement of the space-charge electric field is also described. In particular an approximate solution to Stepanov and Petrov's enhancement method of using AC external electric field is extended to a general case that describes the transient behavior for AC external electric field of arbitrary waveform. The anisotropic refractive index change due to the space-charge field formation is then described in terms of tensorial forms of the nonlinear susceptibility.
\r\n\r\nIn the second part, anisotropic beam coupling in photorefractive crystals is presented and a general set of coupled-wave equations that describes beam coupling in amplitude, phase, and polarization is derived by using the nonlinear and tensorial susceptibility. The polarization properties of the interacting waves are particularly stressed. Two limiting cases, i.e., one for scalar beam coupling and the other for cross-polarization beam coupling, are obtained from the general expression and solved. Experimental results of beam coupling in semi-insulating GaAs are presented, and the signs of dominant charge carriers and the density of photorefractive species are estimated from beam-coupling gain. The enhancement of beam-coupling gain and its temperature dependence are also discussed.
\r\n\r\nIn the third part, four-wave mixing for scalar and vector phase conjugation is described. Self-pumped phase-conjugate mirrors using photorefractive crystals are presented and one of the most interesting properties of these mirrors, i.e., the response to phase changes of inputs, is emphasized both theoretically and experimentally.
\r\n\r\nIn the fourth part, two-wave and four-wave mixing in photorefractive crystals are applied to moving object detection, mathematical operation on images, and one-way image transmission through phase-distorting media. In these applications, polarization properties of interacting waves are particularly utilized.
\r\n\r\nIn the fifth part, a novel method of vector phase conjugation by modal dispersal and scalar phase conjugation is discussed. The propagation characteristics of conjugate waves in strongly scattering media (e.g., mode-scrambling multimode fibers) are described theoretically, followed by the experimental demonstration of vector phase conjugation. In the theory the unitarity and time-reversal symmetry of the scattering matrix are incorporated into the analysis of the coherency matrix of the conjugate field. This theory which describes the physical process of the generation of vector phase conjugation can successfully explain the experimental results of its fidelity.
\r\n\r\nIn the last part, we describe experiments in which the new concept of modal dispersal of information and scalar phase conjugation is used for several novel applications that include nonreciprocal polarization-distortion correction, amplitude-distortion correction, and phase-conjugate multimode fiber-optic sensors. Experiments as well as proposals for these applications are presented.
", "doi": "10.7907/vjga-q464", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:501", "collection": "thesis", "collection_id": "501", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02052007-093221", "type": "thesis", "title": "Properties of Buried Heterostructure Single Quantum Well (Al,Ga)As Lasers", "author": [ { "family_name": "Derry", "given_name": "Pamela Louise", "clpid": "Derry-Pamela-Louise" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Gould", "given_name": "Roy Walter", "clpid": "Gould-R-W" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Unlike conventional semiconductor lasers, single quantum well (SQW) lasers with high reflectivity end facet coatings have dramatically reduced threshold currents as a result of the smaller volume of the (active) quantum well region. A cw threshold current of 0.55 mA was obtained for a buried graded-index separate-confinement heterostructure SQW laser with facet reflectivities of ~80%, a cavity length of 120 \u00b5m, and an active region stripe width of 1 \u00b5m. This is believed to be the lowest threshold current so far reported for any semiconductor laser at room temperature.
\r\n\r\nThe submilliampere threshold currents of these lasers allow them to be modulated at high speed without any current prebias or feedback monitoring. The relaxation oscillation frequency for these lasers was also measured. Values of differential gain derived from these measurements demonstrated that the differential gain in the uncoated lasers is less than in the coated devices. This result was expected because of gain saturation.
\r\n\r\nAs predicted, SQW lasers have substantially narrower spectral linewidths than bulk double heterostructure lasers. This result is attributed to lower internal loss, linewidth enhancement factor, and spontaneous emission factor. A further major reduction (< 3x) in the linewidth of these SQW lasers was observed when the facet reflectivities were enhanced. This observation is explained theoretically on the basis of the very low losses in coated SQW lasers and the value of the spontaneous emission factor.
", "doi": "10.7907/WSZC-4R60", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:553", "collection": "thesis", "collection_id": "553", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02082007-125156", "type": "thesis", "title": "Theory and Experiments on Unstable-Resonator and Quantum Well GaAs/GaAlAs Lasers", "author": [ { "family_name": "Mittelstein", "given_name": "Michael", "clpid": "Mittelstein-Michael" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Structures of GaAs/GaA1As lasers and their performance characteristics are investigated experimentally and theoretically. A self-consistent model for the longitudinal gain and intensity distribution in injection lasers is introduced. The model is applied to unstable-resonator semiconductor lasers to evaluate their lateral losses and quantum efficiencies, and an advanced design is presented. Symmetric, unstable-resonator semiconductor lasers are manufactured and a virtual source point inside the laser more than an order of magnitude narrower than the width of the near field is demonstrated. Young's double-slit experiment is adopted for lateral coherence measurements in semiconductor lasers. A high degree of lateral coherence is found, indicating operation of the unstable-resonator lasers in predominantly one mode.
\r\n\r\nIn the pulsed measurements on broad-area, single-quantum-well, graded-index wave-guide, separate-confinement-heterostructure lasers, very high quantum efficiencies, very low losses, and very high output powers are observed. The devices are found to exhibit beam divergence narrower than two times the diffraction limit in single-lobed, far-field patterns. Using these single-quantum-well lasers, the \"second quantized-state lasing\" is found experimentally, and a simple model is developed to explain it.
\r\n\r\nA general model for the gain spectrum and required current density of quantum-well lasers is introduced. The eigenfunctions and eigenvalues of the charge carriers and optical mode of the transverse structure are used to derive the gain spectrum and current density from the Einstein coefficients. The two-dimensional density of states for the charge carriers and the effective width of the optical mode (not the width of the quantum well) are identified as the dominant parameters. The model includes a new heuristic approach to account for the observed smeared onset of subbands, eliminating convolution calculations.
\r\n\r\nApplications of the model for a typical structure, a conventional double heterostructure and an advanced structure are presented. Structures providing two- and three-dimensional confinement are discussed and are directly compared to conventional and quantum-well structures in terms of laser parameters. The length scale of confinement structures for the optical mode is found to be two orders of magnitude larger than the corresponding length scale for carrier confinement, implying that the single-quantum-well laser is the most adapted structure.
\r\n\r\nThe gain-flattened condition that single-quantum-well lasers exhibit near the onset of the second quantized-state lasing is introduced. An external grating-tuned resonator is analyzed, and the coupled cavity formalism is employed to examine conditions for continuous tuning. Predictions for tuning ranges of conventional, double-heterostructure and single-quantum-well lasers are made, and the superiority of the latter on account of pump current density is clarified. Experimentally, broadband tunability exceeding a 10% spectral tuning range of an uncoated quantum-well laser in a simple grating-tuned resonator is demonstrated.
", "doi": "10.7907/p3k2-pp58", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:1630", "collection": "thesis", "collection_id": "1630", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05052006-103604", "primary_object_url": { "basename": "Rakuljic_ga_1987.pdf", "content": "final", "filesize": 3875425, "license": "other", "mime_type": "application/pdf", "url": "/1630/1/Rakuljic_ga_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Photorefractive Properties and Applications of Barium Titanate and Tungsten Bronze Ferroelectrics", "author": [ { "family_name": "Rakuljic", "given_name": "George Anthony", "clpid": "Rakuljic-George-Anthony" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Beck", "given_name": "James L.", "clpid": "Beck-J-L" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is an experimental and theoretical investigation of the photorefractive properties of barium titanate and tungsten bronze ferroelectrics, and applications thereof. In the first part, the physics of the photorefractive effect is presented. The band transport equations are solved for three cases that describe the photorefractive mechanism in a crystal with one photorefractive species and either one or two types of charge carriers, or in a crystal with two photorefractive species, but only one type of charge carrier.
\r\n\r\nIn the second part, the coupled wave theory of two-wave mixing in photorefractive crystals is reviewed. Effects of energy coupling between the two interacting beams are discussed along with experimental methods for determining the two-beam coupling coefficient and the photorefractive response time.
\r\n\r\nThe photorefractive crystals barium titanate, strontium barium niobate, and barium strontium potassium sodium niobate are described in the third part. A summary of their optical, physical and electrical properties is presented for use in subsequent sections of the thesis.
\r\n\r\nIn the fourth part, the photorefractive properties of these crystals are presented. Data from two-beam coupling experiments are used to obtain the two-beam coupling coefficients and the photorefractive response times of the crystals under a variety of experimental conditions. The band transport models are then applied to these results.
\r\n\r\nFigures of merit are defined in the fifth part that are then used in a comparison of several photorefractive materials, including the barium titanate, the strontium barium niobate, and the barium strontium potassium sodium niobate crystals. Both ferroelectric and non-ferroelectric materials are considered.
\r\n\r\nIn the last part, applications using barium titanate and the tungsten bronze ferroelectrics are described. By using the self-focusing properties of barium titanate and strontium barium niobate, the compensation of nonlinear optical distortions with phase conjugation is demonstrated. A passive phase conjugator that relies on no external mirrors and uses strontium barium niobate as the nonlinear medium is also described. Finally, a thresholding passive phase conjugate mirror is then presented along with several devices that can perform mathematical operations on images such as subtraction and differentiation.
", "doi": "10.7907/8w0w-ea37", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:856", "collection": "thesis", "collection_id": "856", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03032008-143205", "primary_object_url": { "basename": "Lindsey_cp_1987.pdf", "content": "final", "filesize": 9992942, "license": "other", "mime_type": "application/pdf", "url": "/856/1/Lindsey_cp_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "High Power Phased Array and Tailored Gain Semiconductor Lasers", "author": [ { "family_name": "Lindsey", "given_name": "Christopher Paul", "clpid": "Lindsey-Christopher-Paul" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Cohen", "given_name": "Donald S.", "clpid": "Cohen-D-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Most phase locked semiconductor laser arrays suffer from undesirable twin lobed farfield patterns, making them unsuitable for many applications. In this thesis we make a detailed theoretical and experimental study of this problem, and solve it by tailoring the spatial gain profile across the array. We demonstrate a tailored gain chirped array which emits 450mW into a single beam 3\u00bd\u00b0 wide.
\r\n\r\nStripe geometry lasers for use in phased arrays are examined in Chapter 2, as are design considerations for evanescently coupled phased arrays. A powerful numerical method for analyzing a nearly arbitrary one-dimensional dielectric waveguide with gain and/or loss is described.
\r\n\r\nChapter 3 analyzes in detail the simplest array of two adjacent waveguides, both real index and gain guided and both weakly and strongly coupled. Chapter 4 discusses why a uniform array has a twin lobed farfield pattern, and introduces the concept of a nonuniform real index guided chirped array of lasers with widths which increase monotonically across the array. Real index guided chirped arrays can, in principle, be made to lase with a single lobed farfield pattern. Since such arrays are difficult to fabricate, and will be at least partially gain guided, we concentrate on gain guided structures. The combination of gain tailoring and a high interchannel gain in a proton implanted chirped array enables us to achieve our goal of fabricating a high power array with the single lobed farfield pattern described above.
\r\n\r\nSuch arrays are actually tailored gain broad area lasers. Chapter 5 demonstrates another method for gain tailoring, the \"halftone\" process, which can create nearly arbitrary two-dimensional spatial gain profiles in an optoelectronic device, thereby offering a new degree of freedom to the designer of semiconductor lasers. Single lobed nearly diffraction limited beams from tailored gain broad area lasers 50\u00b5m wide are obtained.
\r\n\r\nAsymmetric tailored gain waveguides have several unusual properties. The technique of Path Analysis for analyzing these complex waveguides is introduced. Fundamental Fourier Transform relationships relating device structure to farfield patterns yield additional insights. Finally, we close with a measurement of the antiguiding parameter and briefly examine some design criteria for practical tailored gain broad area lasers.
\r\n", "doi": "10.7907/9mh8-wv40", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:11829", "collection": "thesis", "collection_id": "11829", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10182019-170044100", "type": "thesis", "title": "Theory and Applications of Wave-Mixings in Photorefractive Crystals", "author": [ { "family_name": "Kwong", "given_name": "Sze-Keung", "clpid": "Kwong-Sze-Keung" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Gomez", "given_name": "Ricardo", "clpid": "Gomez-R" }, { "family_name": "Zachariasen", "given_name": "Fredrik", "clpid": "Zachariasen-F" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis is an experimental and theoretical investigation of wave-mixing in photorefractive crystals and applications thereof. In the first part, the physics of the photorefractive effect is described. The figures of merit useful in characterizing various photorefractive crystals are also discussed.
\r\n\r\nIn the second part, the coupled wave theory of two interacting optical waves in photorefractive crystals is reviewed. Both the energy coupling and the phase delay of the two beams are analyzed.
\r\n\r\nIn the third part, the coupled wave formalism is extended to four wave mixing in photorefractive crystals. Aspects of real-time holography and phase conjugation are discussed. The coupled wave equations are solved in two special cases: (1) single grating and undepleted pump approximation; and (2) single grating and negligible absorption. The theory is then compared with the experimental results. The solutions of the phase of phase conjugation are presented. The recent developments in self-pumped phase conjugate mirrors are also discussed.
\r\n\r\nIn the fourth part, new types of oscillators ultilizing the photorefractive gain are described and demonstrated. Two approaches to derive the conditions for unidirectional ring oscillation are presented and compared. The theory and experimental demonstration of a double phase conjugate resonator are described. Two applications, the optical path length to frequency conversion interferometer and the one-way real time wave front converters, are also described.
\r\n\r\nIn the last part, some applications of the previous studies are described. Two novel bistable devices using the self-pumped phase conjugate mirror are demonstrated. Mathematical operations on images, such as real time 'exclusive or' operation, image subtraction, differentiation, and intensity inversion are demonstrated using an interferometer with a self-pumped phase conjugate mirror. Finally, the theory and the experimental demonstration of an all-optical associative holographic memory are discussed . Methods of extending the number of stored messages are also discussed.
", "doi": "10.7907/atwv-t152", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:901", "collection": "thesis", "collection_id": "901", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03082008-083912", "primary_object_url": { "basename": "Smith_js_1986.pdf", "content": "final", "filesize": 9510713, "license": "other", "mime_type": "application/pdf", "url": "/901/1/Smith_js_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "III-V Molecular Beam Epitaxy Structures for Electronic and Optoelectronic Applications", "author": [ { "family_name": "Smith", "given_name": "John Stephen", "clpid": "Smith-John-Stephen" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Corngold", "given_name": "Noel Robert", "clpid": "Corngold-N-R" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Molecular beam epitaxy (MBE), a method for depositing epitaxial semiconductor layers with an extreme degree of control, has previously been limited largely to featureless substrates. This thesis describes a procedure for high quality MBE growth over finely patterned GaAs substrates, which is suitable for device fabrication requiring lateral definition of small (~ 1-2 micron) dimension. The results of series of experiments determining the characteristics of MBE growth over patterned substrates are presented. Temperature and flux ratio dependence of faceting during MBE growth over patterned substrates is shown for temperatures ranging from 580\u00b0 C to 700\u00b0 C and for As/Ga flux ratios from 1.4:1 to 4:1, and surface diffusion lengths for gallium are measured. The (811) and (411) facets are shown to have growth rates which are at a local maximum and minimum, respectively, for facets tilted in the [01̅1] direction, and implications with respect to other experiments on the atomic growth kinetics on (100) facets are discussed. The material grown over facets tilted in the [0111 direction is shown to be of high quality, with electroluminescence equal to that over the (100) plane.
\r\n\r\nThis method was used for the fabrication of an index guided laser structure, with an optical guide similar to that of the liquid phase grown channeled substrate planer laser structure, as well as tightly packed arrays of these lasers. Yields of individual lasers exceeded 90 percent, and thresholds were uniform to 10 percent. Other potential applications for this technique include a vertical structure high electron mobility transistor, formation of \"quantum wire\" structures, and methods of directly contacting quantum well layers for device applications and research purposes.
\r\n\r\nCertain aspects of transport of hot electrons over quantum wells are discussed, with application to several types of devices, including a new type of infrared detector structure, a solid state electron multipler, and a proposed quantum well base transistor.
", "doi": "10.7907/r489-8025", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:4556", "collection": "thesis", "collection_id": "4556", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11142007-081143", "primary_object_url": { "basename": "Lang_rj_1986.pdf", "content": "final", "filesize": 10764645, "license": "other", "mime_type": "application/pdf", "url": "/4556/1/Lang_rj_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Semiconductor Lasers: New Geometries and Spectral Properties", "author": [ { "family_name": "Lang", "given_name": "Robert James", "orcid": "0000-0001-9496-123X", "clpid": "Lang-Robert-James" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is an investigation into the spectral properties of two broad classes of semiconductor lasers. They are (1) broad-area lasers with non-planar mirrors, specifically, those with an unstable resonator configuration, and (2) coupled-cavity semiconductor lasers.
\r\n\r\nThe use of non-planar mirrors on broad-area lasers can substantially improve their properties. Chapter 2 focuses on the experimental realization of several unstable resonator semiconductor lasers, while chapter 3 presents a method of analyzing the modes of such a device.
\r\n\r\nCoupling two cavities together can drastically alter the dynamic and spectral properties of a semiconductor laser. In chapter 4 we present experimental measurements and explain the properties of a laser consisting of two side-by-side coupled cavities. We then turn to the theoretical problem of analyzing the dynamic properties of multicavity lasers. In chapter 5, we derive a general expression for the dynamic response of a multielement laser. In the process, we develop a formalism for treating the dynamics of any semiconductor laser system with particular ease of application to single-mode multielement lasers. In chapter 6, we show that 2 or more cavities can lead to bistability and bimodality. The quantum fluctuation-induced noise properties of multicavity lasers are analyzed in chapter 7. In chapter 8, we return to the single-element laser and calculate non-quantum noise contributions--specifically, thermal and diffusion noise-- which give rise to a 1/f spectrum. In chapter 9 we present a new method of deriving multicavity rate equations and point out a shortcoming of the existing coupled-mode treatments.
\r\n", "doi": "10.7907/rk0z-ma09", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:543", "collection": "thesis", "collection_id": "543", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02082005-114440", "primary_object_url": { "basename": "Vahala_kj_1985.pdf", "content": "final", "filesize": 4779219, "license": "other", "mime_type": "application/pdf", "url": "/543/1/Vahala_kj_1985.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Dynamic and Spectral Features of Semiconductor Lasers", "author": [ { "family_name": "Vahala", "given_name": "Kerry John", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-Kerry-John" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Knowles", "given_name": "James K.", "clpid": "Knowles-J-K" } ], "thesis_committee": [ { "family_name": "Knowles", "given_name": "James K.", "clpid": "Knowles-J-K" }, { "family_name": "Sternberg", "given_name": "Eli", "clpid": "Sternberg-E" }, { "family_name": "Wu", "given_name": "Theodore Yao-tsu", "clpid": "Wu-T-Y-T" }, { "family_name": "Knauss", "given_name": "Wolfgang Gustav", "clpid": "Knauss-W-G" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is divided into two main subject areas: the fluctuation properties of state of the art semiconductor lasers and the improvement of modulation and fluctuation properties in these devices through a technique called detuned loading.
\r\n\r\nThe discussion of fluctuations in lasers is a topic as old as the device itself, and much of the pioneering work in this field was done in the sixties. Surprisingly, however, several new chapters in this field are being written, because of certain pecularities only recently observed in semiconductor lasers. Chapters 2 and 3 of this thesis will consider these pecularities, which, as it turns out, are quite important in many potential system applications of these devices.
\r\n\r\nOne of the driving forces behind the development of semiconductor lasers has been their application as sources and local oscillators in optical communication systems. In general, such applications require lasers which have low phase and intensity noise, and which can be modulated at high data rates. As is often the case, these requirements are to a certain extent mutually exclusive. Chapter 4 introduces a technique which is an exception to this rule. It relies upon the semiconductor laser physics which produces the fluctuation abnormalities discussed in Chapters 2 and 3. The technique can be used to improve modulation speed while simultaneously reducing noise as compared to the conventional device.
", "doi": "10.7907/H7JA-K512", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:240", "collection": "thesis", "collection_id": "240", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01192007-152414", "type": "thesis", "title": "Four-Wave Mixing and Phase Conjugation in Photorefractive Crystals", "author": [ { "family_name": "White", "given_name": "Jeffrey Owen", "orcid": "0000-0003-3109-193X", "clpid": "White-Jeffrey-Owen" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Kath", "given_name": "William L.", "clpid": "Kath-William-L" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is an experimental and theoretical investigation of nonlinear optics in photo-refractive crystals, and applications thereof. Coherent light is used to induce nonlinear, optical frequency polarizations proportional to the cube of the total optical field within these materials. Equivalently, dynamic holography performed wherein the incident light simultaneously writes, reads and erases index of refraction gratings.
\r\n\r\nThe first part of this thesis is a description of the physics of the photo-refractive effect in such crystals as Bi12SiO20, LiNbO3, KTaO3, and BaTiO3. Previous microscopic rate equation models are extended to include the dynamics of a second photo-refractive center with the aim of explaining several discrepancies with experimental data.
\r\n\r\nThe second part reviews the coupled wave theory of fixed gratings and dynamic gratings formed in photo-refractive media. Coupled nonlinear ordinary differential equations describe the interaction between two optical waves; which is caused by the grating that they create. The analysis is extended to the reflection geometry and the ring resonator geometry. The coupling constant is measured in the reflection geometry. Holographic gain is combined with mirror feedback to demonstrate a unidirectional ring oscillator, wherein a optically pumped photo-refractive crystal functions as a directional gain element.
\r\n\r\nThe third part extends the analysis to the holographic formulation of four-wave mixing, wherein four waves and up to four gratings exist in the crystal. The equations are solved in the single grating approximation. The object of much of the analysis is to calculate the reflectivity of a four-wave mixing photo-refractive phase conjugate mirror. The invention of a passive self-pumped phase conjugate mirror is described.
\r\n\r\nThe last part describes three applications of four-wave mixing. We demonstrate the compensation of intracavity laser distortions by replacing an ordinary mirror in a laser with a passive phase conjugate mirror. We propose and demonstrate a phase conjugate window for one-way transmission of an information bearing optical field through a thin phase distortion. Finally, the multiplicative properties of four-wave mixing are combined with the transforming properties of lenses to construct a coherent optical processor capable of convolving and correlating three input fields containing arbitrary spatial phase and amplitude information.
", "doi": "10.7907/f9ef-m894", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:295", "collection": "thesis", "collection_id": "295", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01232007-131641", "primary_object_url": { "basename": "Yu_kl_1984.pdf", "content": "final", "filesize": 4579274, "license": "other", "mime_type": "application/pdf", "url": "/295/1/Yu_kl_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Long Wavelength InGaAsP/InP Lasers and Optoelectronic Integration", "author": [ { "family_name": "Yu", "given_name": "Paul Kit-Lai", "clpid": "Yu-Paul-Kit-Lai" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Margalit", "given_name": "Shlomo", "clpid": "Margalit-Shlomo" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Neugebauer", "given_name": "Gerry", "clpid": "Neugebauer-G" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The light sources for optical communications in the 1.3-1.5 \u00b5m range are the quaternary InGaAsP/InP lasers which emit in this low loss region of optical fibers. The structure and properties of some lasers fabricated in this material system as well as their integration into optoelectronics are treated in this thesis.
\r\n\r\nLasers exhibiting low threshold, high power and stable far field are extremely desirable in communication systems. Selective epitaxial growth offers an elegant yet powerful technique of fabricating laser structures with these properties. Its application to, as well as properties of, the resulting laser structures are presented. In particular, a laser with high output power is demonstrated.
\r\n\r\nTo further extend the operating power of index guided laser diodes in a stable fundamental mode, gain stabilization is proposed as an effective means of discriminating against higher order transverse mode operation. The optimal design for gain stabilized fundamental mode operation is formulated theoretically and verified experimentally.
\r\n\r\nPrecipitous increase of threshold current with temperature has been observed in some InGaAsP/InP lasers. Electron leakage over the heterobarrier has been identified as the cause of this abnormality. The origin as well as the control of these leaked carriers is studied.
\r\n\r\nAdvances in optoelectronic integration consisting of diffraction coupled arrays and the demonstration of Laser-MISFET devices and the technique of microcleaved mirrors are described in detail.
\r\n\r\nThe microcleavage technique is applied to the fabrication of very short cavity lasers. The advantages of short cavities are presented.
\r\n", "doi": "10.7907/4dk7-wn36", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:3355", "collection": "thesis", "collection_id": "3355", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-083609", "primary_object_url": { "basename": "Harder_cs_1983.pdf", "content": "final", "filesize": 11181635, "license": "other", "mime_type": "application/pdf", "url": "/3355/1/Harder_cs_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Bistability, High Speed Modulation, Noise and Pulsations in GaAlAs Semiconductor Lasers", "author": [ { "family_name": "Harder", "given_name": "Christoph S.", "clpid": "Harder-Christoph-S" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Peck", "given_name": "Charles W.", "clpid": "Peck-C-W" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "McCaldin", "given_name": "James Oeland", "clpid": "McCaldin-J-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes seven different subjects relevant to semiconductor laser diodes which fall in the following three categories: Bistability and pulsations, high speed modulation and noise.
\r\n\r\nBistable semiconductor lasers based on inhomogeneous current injection, achieved with a split contact scheme, were proposed around 20 years ago. However, actual devices showed no or only a small hysteresis and they were in addition beset by pulsations for reasons not well understood at the time. In this thesis we show that lasers with an optimized design can display bistability with a giant hysteresis. Crucial to the understanding of the bistable laser is a negative differential resistance across the absorber section, reminiscent of a tunnel diode characteristic. Depending on the electrical biasing circuit this negative differential resistance leads to bistability or light-jumps and self-pulsations. A simple model based on the conventional rate equations explains the observed behavior. Investigation of the switching dynamics of this optoelectronic device reveals a delay time which is critically dependent on the trigger pulse amplitude and which is typically in the order of a few nanoseconds at a power-delay product of 100pJ. We also investigate the characteristic of this laser coupled to an external optical cavity and we demonstrate that this bistable laser can be used as a self-coupled stylus for optical disk readout. Under a different biasing condition this laser coupled to an external optical cavity can be used to generate ultrashort optical pulses through passive mode locking. Unlike previous mode locking techniques, the method presented here does not rely on absorption introduced by damaging the crystal and is consequently much more reliable.
\r\n\r\nThe high speed modulation behavior of semiconductor lasers is investigated theoretically and experimentally. In this thesis we derive the fundamental limits of injection lasers for pulse modulation and small signal modulation. We place emphasis on developing laser structures optimized for high frequency modulation and experiments on such structures show that they can be modulated at frequencies up to 8GHz. At these frequencies the parasitic elements can no longer be neglected and they are included in the analysis.
\r\n\r\nThe noise equivalent circuit of a semiconductor laser diode is derived from the rate equations including Langevin noise sources. This equivalent circuit allows a straightforward calculation of the noise and frequency modulation characteristics of a laser diode combined with electronic components. The field spectrum of injection lasers is observed also experimentally. It is a unique feature of injection lasers that their linewidth is increased through a strong amplitude phase coupling by the factor (1 + \u03b12) where \u03b1 is the linewidth enhancement factor. A model is developed which shows that the same factor \u03b1 enters in the small signal modulation characteristics and a careful measurement of the small signal amplitude and phase modulation at high frequencies enables us to obtain this important factor \u03b1 for the first time by a direct measurement.
", "doi": "10.7907/jxwz-e844", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3360", "collection": "thesis", "collection_id": "3360", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-131347", "type": "thesis", "title": "III-V Semiconductor Lasers and Detectors", "author": [ { "family_name": "Chiu", "given_name": "Liew-Chuang", "clpid": "Chiu-Liew-Chuang" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" }, { "family_name": "Margalit", "given_name": "Shlomo", "clpid": "Margalit-Shlomo" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Whaling", "given_name": "Ward", "clpid": "Whaling-W" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The subjects of this thesis can be divided into two main categories: III-V semiconductor lasers and detectors. The first two chapters are concerned with the InGaAsP/InP laser diodes. The final two chapters are related to fundamental problems in the avalanche photodiodes and the new class of quantum well infrared detectors.
\r\n\r\nThe kinetics of the mass transport phenomenon in InP is studied experimentally. Application of this technique to laser fabrication has resulted in very low threshold terrace mesa lasers.
\r\n\r\nThe continuing problem of the excess temperature sensitivity of InGaAsP lasers and light emitting diodes is studied in detail. Non-radiative Auger recombination and electron leakage are found to be important factors affecting the temperature sensitivities of these devices.
\r\n\r\nImpact ionization in the GaAlSb system is investigated. The resonant nature of the enhanced impact ionization of holes is discussed. Further enhancement is predicted to be possible in quantum well structures.
\r\n\r\nThe new class of quantum well infrared detectors is described. Theoretical considerations on absorption coefficients and other parameters essential to device design and performance are discussed.
", "doi": "10.7907/ttgs-8a70", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3373", "collection": "thesis", "collection_id": "3373", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09072006-080636", "type": "thesis", "title": "New Structures for AlGaAs Lasers and Avalanche Photodetectors", "author": [ { "family_name": "Blauvelt", "given_name": "Henry A.", "clpid": "Blauvelt-Henry-A" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "McCaldin", "given_name": "James Oeland", "clpid": "McCaldin-J-O" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Goodstein", "given_name": "David L.", "clpid": "Goodstein-D-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes the fabrication and the properties of five new semiconductor laser diode structures. All of these devices were grown from the GaAs-AlGaAs ternary system using the liquid phase epitaxial technique. In addition, a new low noise avalanche photodetector is proposed.
\r\n\r\nThe first example is a new technique for fabricating cleaved mirrors without cleaving through the substrate. This technique, called micro-cleavage, has potential applications for both opto-electronic integrated circuits and for the fabrication of short cavity length lasers. In this technique, cantilevers are formed by a sequence of etching steps. These cantilevers are subsequently cleaved using ultrasonic vibrations.
\r\n\r\nThree devices related to high power single mode lasers are described. The first of these is the large optical cavity buried heterostructure window laser. The output power of semiconductor lasers, particularly during pulsed operation is limited by catastrophic mirror damage which occurs at power densities above a pulse width dependent damage threshold. The damage occurs due to local heating up to the melting point of the active region in the vicinity of the cleaved mirror facets. However, catastrophic mirror damage can be avoided by isolating the active layer from the cleaved mirrors, as is done in these window lasers. The second device related to high power that is described is the Inverted Strip Buried Heterostructure laser. These lasers combine many of the best features of both the buried optical guide lasers and the strip buried heterostructure that have been previously developed elsewhere. The inverted strip buried heterostructure lasers have significantly better beam quality than buried optical guide lasers and can be operated in the fundamental spatial mode for larger emitting areas (and therefore greater output power). The third device related to high power lasers is a variation of a buried heterostructure laser in which the injected current is confined to a narrow section in the center of the active layer. The optical gain is therefore also confined to a narrow section in the center of the active layer. By doing so the fundamental mode is much better matched to the optical gain than the higher order spatial modes. The result is that fundamental mode operation is possible for buried heterostructure lasers with active layer widths up to 8 \u00b5m. When the current is injected uniformly into the active layer, fundamental mode operation is possible only for active layer widths less than 2 \u00b5m. In addition to the descriptions of these devices a theoretical chapter on high power single mode lasers is included.
\r\n\r\nThe final laser structure that is described is a single liquid phase epitaxial growth laser structure in which the current is restricted to flow between two narrow stripes located above and below the active layer. This structure, which is fabricated using a meltback-growth technique allows the current injection to be restricted to a very narrow section of the active layer, which results in several interesting properties which are described and explained using a simple model.
\r\n\r\nThe final subject of this thesis is a multilayer avalanche photodetector (APD) which has been proposed for low noise applications. The noise generated by an APD is dependent on the statistics of the carrier multiplication process, since positive feedback effects, which exist when both electrons and holes produce secondary pairs, can greatly amplify any current fluctuations. Significantly more noise is generated if the electron and hole ionization rates (\u03b1, \u03b2) are equal than if only one carrier produces secondary pairs. The multilayer structure described and analyzed in this chapter is expected to have impact ionization which is dominated by electrons and therefore would be of importance for low noise applications.
", "doi": "10.7907/DJMZ-S785", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3920", "collection": "thesis", "collection_id": "3920", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10042006-130634", "type": "thesis", "title": "Gigawatt Picosecond Dye Lasers and Ultrafast Processes in Semiconductor Lasers", "author": [ { "family_name": "Koch", "given_name": "Thomas Lawson", "clpid": "Koch-Thomas-Lawson" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Zewail", "given_name": "Ahmed H.", "clpid": "Zewail-A-H" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is a theoretical and experimental investigation of a gigawatt picosecond dye laser oscillator-amplifier system, and the application of that system to the study of ultrafast lasing and carrier dynamics in semiconductor lasers.
\r\n\r\nBeginning with a review of traveling wave rate equations, nonlinear pulse propagation in a generalized two-level amplifying/absorbing medium is discussed. This permits a qualitative treatment of synchronously mode-locked dye lasers. The formalism is then refined to provide a quantitative analysis of picosecond dye laser amplifier chains, including amplified spontaneous emission, saturable absorbers used for amplifier stage isolation, gain saturation with \"angular hole-burning\" and triplet losses, and linear and nonlinear pulse shaping effects.
\r\n\r\nExperimentally, the construction and operation of a three stage Nd:YAG laser pumped picosecond dye laser amplifier chain is described. Numerical modeling is used to compare the theoretical analysis with the experimental results. In addition, a brief discussion of picosecond time domain measurement techniques is presented, focussing on nonlinear optical methods. This includes a parametric sum frequency upconversion gating technique used extensively in this work to provide linear, picosecond resolution temporal measurements of optical pulses which are synchronized to the dye laser pulses.
\r\n\r\nThe output of the picosecond dye laser system is used to optically generate high carrier densities in semiconductor lasers, and the ensuing short pulse lasing dynamics are investigated and compared to the predictions of a simple rate equation analysis. Novel effects are observed in the spectrally resolved temporal measurements of the lasing output from picosecond optically pumped buried heterostructure semiconductor lasers. A model is developed which includes both broadband stimulated emission as well as many-valley and hot electron effects in the semiconductor, and the model is in close agreement with the observed behavior. The conclusion is drawn that the picosecond lasing dynamics of semiconductor lasers can be understood if the conventional rate equations are abandoned in favor of a more fundamental analysis which includes not just the dynamics of the optical energy exchange in the laser cavity, but the detailed picosecond dynamics of the semiconductor material as well.
\r\n", "doi": "10.7907/61ca-rp72", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:3519", "collection": "thesis", "collection_id": "3519", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09132006-133617", "type": "thesis", "title": "Long Wavelength GaInAsP/InP Semiconductor Lasers for Optical Communications", "author": [ { "family_name": "Chen", "given_name": "Pei-Chuang", "clpid": "Chen-Pei-Chuang" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical fiber communication systems have shifted toward the long wavelength range of 1.2-1.6 \u00b5m due to lower losses and dispersion available with high quality fibers. The quaternary GaInAsP/InP material system has evolved as the most promising system for light sources in this range.
\r\n\r\nIndium phosphide electronic devices are expected to possess high frequency switching capabilities, but present device technology is still rather primitive. In anticipation of future developments, which will render opto-electronic integration in this system advantageous, two laser structures on semi-insulating InP substrates were demonstrated. The substrate permits electrical isolation between components and thus is ideal in planar integration of the lasers with electronic devices.
\r\n\r\nLow threshold lasers can only be achieved when the active region is properly defined in two dimensions to provide good optical and carrier confinement. Present techniques usually require difficult and intricate growth step of two-step liquid phase epitaxy. Embedded epitaxy, by growth through a mask, offers a simple yet elegant means of two dimensional definition of the active region with only a single growth step. Low threshold lasers were fabricated with this technique and demonstrated its potential applications.
\r\n\r\nAll GaInAsP/InP lasers show accelerated increase of threshold current with temperature of a different nature than similar GaA1As lasers. To understand the origin of this phenomenon, calculations were made of the Auger process in these lasers, and have demonstrated that they play a very important role in the temperature behavior of GaInAsP/InP lasers.
\r\n", "doi": "10.7907/51sv-sm58", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:8081", "collection": "thesis", "collection_id": "8081", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02182014-143316560", "primary_object_url": { "basename": "Nilsen_jm_1982.pdf", "content": "final", "filesize": 31204492, "license": "other", "mime_type": "application/pdf", "url": "/8081/1/Nilsen_jm_1982.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Phase Conjugation via Four-Wave Mixing in a Resonant Medium", "author": [ { "family_name": "Nilsen", "given_name": "Joseph Michael", "clpid": "Nilsen-Joseph-Michael" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Whaling", "given_name": "Ward", "clpid": "Whaling-W" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis describes the theoretical solution and experimental verification of phase conjugation via nondegenerate four-wave mixing in resonant media. The theoretical work models the resonant medium as a two-level atomic system with the lower state of the system being the ground state of the atom. Working initially with an ensemble of stationary atoms, the density matrix equations are solved by third-order perturbation theory in the presence of the four applied electro-magnetic fields which are assumed to be nearly resonant with the atomic transition. Two of the applied fields are assumed to be non-depleted counterpropagating pump waves while the third wave is an incident signal wave. The fourth wave is the phase conjugate wave which is generated by the interaction of the three previous waves with the nonlinear medium. The solution of the density matrix equations gives the local polarization of the atom. The polarization is used in Maxwell's equations as a source term to solve for the propagation and generation of the signal wave and phase conjugate wave through the nonlinear medium. Studying the dependence of the phase conjugate signal on the various parameters such as frequency, we show how an ultrahigh-Q isotropically sensitive optical filter can be constructed using the phase conjugation process.
\r\n\r\nIn many cases the pump waves may saturate the resonant medium so we also present another solution to the density matrix equations which is correct to all orders in the amplitude of the pump waves since the third-order solution is correct only to first-order in each of the field amplitudes. In the saturated regime, we predict several new phenomena associated with degenerate four-wave mixing and also describe the ac Stark effect and how it modifies the frequency response of the filtering process. We also show how a narrow bandwidth optical filter with an efficiency greater than unity can be constructed.
\r\n\r\nIn many atomic systems the atoms are moving at significant velocities such that the Doppler linewidth of the system is larger than the homogeneous linewidth. The latter linewidth dominates the response of the ensemble of stationary atoms. To better understand this case the density matrix equations are solved to third-order by perturbation theory for an atom of velocity v. The solution for the polarization is then integrated over the velocity distribution of the macroscopic system which is assumed to be a gaussian distribution of velocities since that is an excellent model of many real systems. Using the Doppler broadened system, we explain how a tunable optical filter can be constructed whose bandwidth is limited by the homogeneous linewidth of the atom while the tuning range of the filter extends over the entire Doppler profile.
\r\n\r\nSince it is a resonant system, sodium vapor is used as the nonlinear medium in our experiments. The relevant properties of sodium are discussed in great detail. In particular, the wavefunctions of the 3S and 3P states are analyzed and a discussion of how the 3S-3P transition models a two-level system is given.
\r\n\r\nUsing sodium as the nonlinear medium we demonstrate an ultrahigh-Q optical filter using phase conjugation via nondegenerate four-wave mixing as the filtering process. The filter has a FWHM bandwidth of 41 MHz and a maximum efficiency of 4 x 10-3. However, our theoretical work and other experimental work with sodium suggest that an efficient filter with both gain and a narrower bandwidth should be quite feasible.
\r\n\r\n\r\n\r\n", "doi": "10.7907/RV9B-GV44", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:3621", "collection": "thesis", "collection_id": "3621", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09182006-141505", "type": "thesis", "title": "(AlGa)As Semiconductor Lasers and Integrated Optoelectronics", "author": [ { "family_name": "Wilt", "given_name": "Daniel Paul", "clpid": "Wilt-Daniel-Paul" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Five subjects related to monolithic integration of electronic and optical devices in the (AlGa)As material system are treated in this thesis. They are:
\r\n\r\n1. The Integrated Optoelectronic Repeater:
\r\n\r\nThe design, fabrication, and testing of the first monolithic integrated optical repeater is described. This device consists of an optical detector, electronic gain stage, and current modulated semiconductor laser transmitter integrated in a single crystal chip to perform the function of regenerating an optical signal as might be found in an optical communication system. The device has a measured optical gain (light out to light in) of 10 dB.
\r\n\r\n2. Ion Implanted Lasers and Schottky Gate Field Effect Transistors:
\r\n\r\nThe use of ion implantation as a technique to fabricate both lasers and field effect transistors is described. Devices fabricated include a beryllium implanted laser diode on N type GaAs substrate, a beryllium implanted laser diode on semi-insulating Cr doped GaAs substrate integrated with a field effect transistor driver, and sulfur implanted GaAs field effect transistors.
\r\n\r\n3. A Steady State Lateral Model of the Double Heterostructure Laser:
\r\n\r\nA theoretical model of the double heterostructure laser is described which treats the p-n junction in the device correctly by using fundamental semiconductor relationships and reasonable assumptions about the device heterointerfaces. The model treats both the electronic and optical properties self consistently, making the model valid above lasing threshold. Finite element formalism is adopted as a solution technique to enable the treatment of complicated diode geometries. An example is treated and theoretical and experimental results are compared.
\r\n\r\n4. The Effect of Lateral Carrier Diffusion on the Modulation Response of a Semiconductor Laser:
\r\n\r\nThe effect of lateral carrier diffusion upon the modulation characteristics of the semiconductor laser is investigated. A self consistent analysis of the spatially dependent rate equations is performed using a finite element model. The transverse junction stripe laser is treated as an example and a comparison is made between lateral carrier diffusion and spontaneous emission as damping mechanisms for the resonance peak. Experimental results bear out the conclusion that the relaxation resonance in this device is damped mainly by lateral carrier diffusion. In addition, a simple analytic result is presented which illustrates qualitatively the effect of lateral carrier diffusion upon such devices. The conclusion from this result is that lateral carrier diffusion serves to damp the relaxation resonance in the semiconductor laser quite well, but probably will not serve to improve the upper limit on modulation frequency as might have been suspected.
\r\n\r\n5. Effective Permittivity Formalism and the Design of Buried Heterostructure Lasers:
\r\n\r\nAn approach to effective permittivity formalism is presented which clarifies and extends the use of this technique particularly in the treatment of waveguiding in the semiconductor laser. The scalar wave equation is posed in a variational form, and the effective permittivity formalism is treated as a variational approximation technique. This approach shows clearly the nature and limits of the approximation involved. The formalism is applied to the case of the buried heterostructure laser and the results differ considerably from the conventional application of effective permittivity formalism to this device when a reasonable form is assumed for the variational modal profile.
", "doi": "10.7907/f9jz-ez68", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:52", "collection": "thesis", "collection_id": "52", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01072005-145115", "type": "thesis", "title": "AlGaAs Optoelectronic Devices for Optical Communications", "author": [ { "family_name": "Katz", "given_name": "Joseph", "clpid": "Katz-Joseph" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Peck", "given_name": "Charles W.", "clpid": "Peck-C-W" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Rauch", "given_name": "Lawrence L.", "clpid": "Rauch-Lawrence-L" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes several semiconductor injection laser diodes and related optoelectronic devices that can be used as light sources for optical communication systems, and develops the intrinsic electrical model of the laser diode. All the devices were grown from the GaAs-GaAlAs ternary system using the liquid phase epitaxy technique. The AlGaAs materials are very useful for the fabrication of both optical devices (sources and detectors) and conventional electronic components, due to their optical and electrical properties.
\r\n\r\nThe first device is the Translaser, a monolithically integrated heterostructure bipolar transistor with an injection laser. The next two types of devices possess bistable electrical characteristics. One is a laser-SCR switch, and the second type consists of multi-PN heterostructure devices. Each of the devices described above performs an electronic function, of modulating the light output of the laser associated with it.
\r\n\r\nFinally, two types of low-threshold single-node laser diodes are presented. Their properties make them attractive candidates for sources in optical fiber communication systems. The first one is the Embedded Stripe Laser, and the second one is a new version of the Buried-Heterostructure laser, fabricated on semi-insulating substrates.
\r\n\r\nAn equivalent circuit of the laser diode is presented in the last chapter. This model provides a better understanding of the operation of the laser diode, which is particularly important in applications which involve its high frequency: operation with other electronic components and when a modification of its frequency response is needed.
\r\n", "doi": "10.7907/2AXD-2Z75", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:3918", "collection": "thesis", "collection_id": "3918", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10042006-111807", "type": "thesis", "title": "Ultra-High Frequency Dynamics of Semiconductor Injection Lasers", "author": [ { "family_name": "Lau", "given_name": "Kam-Yin", "clpid": "Lau-Kam-Yin" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Walker", "given_name": "Robert Lee", "clpid": "Walker-R-L" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "Caltech Distinguished Alumni Award" }, { "literal": "div_eng" } ], "abstract": "Experimental and theoretical studies on the high frequency dynamics of (GaAl)As semiconductor lasers center on three main areas: 1) analog modulation response of laser diodes; 2) pulse (pulse code modulation) response of laser diodes and 3) generation and quenching of intensity pulsations in laser diodes coupled to external cavities.
\r\n\r\nThe basic analog modulation and transient characteristics of injection lasers with various structures are studied and compared. The basic limitations on ultrahigh frequency ( > 5GHz) modulation of lasers are considered. Self-pulsations in injection lasers are studied and their interaction with external cavities are clarified. These studies lead to the quenching of self-pulsation and ultra-short short pulse generation in laser diodes by coupling to an external cavity. A novel external fiber resonator is introduced for this purpose. Pattern effects in pulse code modulation of injection lasers are studied and a bipolar pulsing scheme devoid of the above effect is described. The transverse mode shift in a transverse junction laser under ultrashort electrical pulse excitation is investigated. Finally, the frequency response of superluminescent lasers (lasers without mirrors) is analysed.
\r\n", "doi": "10.7907/f057-zj77", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:5152", "collection": "thesis", "collection_id": "5152", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12282005-104818", "primary_object_url": { "basename": "Agmon_p_1980.pdf", "content": "final", "filesize": 7619516, "license": "other", "mime_type": "application/pdf", "url": "/5152/1/Agmon_p_1980.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "I. Design, Control, and Characterization of the Passively Mode Locked CW Dye Laser. II. Photoconductive Impulse Response and Excess Carrier Lifetime of Cr-doped GaAs", "author": [ { "family_name": "Agmon", "given_name": "Pinchas", "clpid": "Agmon-Pinchas" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Smith", "given_name": "Darryl L.", "clpid": "Smith-D-L" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis consists of two parts. The subject of the first part is the design, control, and characterization of the passively mode locked CW dye laser, which is capable of producing a stable continuous train of subpicosecond pulses. Following a description of the laser's elements, the mode stability of its multi-mirror resonator is studied. The monitoring of the laser operational state by pulsewidth and bandwidth measurements is described.
\r\n\r\nIn the second part, the photoconductive impulse response and excess carrier lifetime of semi-insulating Cr:GaAs is studied experimentally and analytically. In the transient photoconductive experiment, the material is irradiated with a continuous train of picosecond light pulses with photon energy above the band-gap energy, generated by the passively mode locked CW dye laser described in part I. A photoconductive decay time of 67 psec is deduced from the observations and interpreted as the result of both bulk and surface recombination. It is shown that it agrees well with longer carrier lifetime in Cr:GaAs measured under steady state conditions with longer illumination wavelengths.
", "doi": "10.7907/hr51-0r95", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:2604", "collection": "thesis", "collection_id": "2604", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06152005-155103", "primary_object_url": { "basename": "Moyer_rh_1980.pdf", "content": "final", "filesize": 4962363, "license": "other", "mime_type": "application/pdf", "url": "/2604/1/Moyer_rh_1980.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "I. The Mode Locked Dye Laser. II. Picosecond Photoconductivity of Semi-Insulating Gallium Arsenide", "author": [ { "family_name": "Moyer", "given_name": "Richard Harrison", "clpid": "Moyer-Richard-Harrison" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The first part of this thesis deals with the principles and practice of the passive mode locking of a CW dye laser. This discussion includes the dynamics of picosecond pulse production as well as the techniques of high resolution pulse width measurement. The characterization of the mode locked dye laser through real-time temporal and spectral measurements is also described.\r\n\r\nThe second part of the thesis describes the development and applications of the opto-electronic semiconductor switch. Design considerations of the high speed photoconductive device and results of experiments in which picosecond pulses activate the devices are discussed. The experimental results are interpreted to yield numerical estimates of carrier recombination rates. A new experimental technique of determining these parameters through ultrafast magnetophotoconductivity is introduced as well. The results of this technique show good agreement with the steady state measurements.", "doi": "10.7907/bhsz-8b41", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:3812", "collection": "thesis", "collection_id": "3812", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09282006-090324", "primary_object_url": { "basename": "Ury_i_1980.pdf", "content": "final", "filesize": 9091260, "license": "other", "mime_type": "application/pdf", "url": "/3812/1/Ury_i_1980.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Monolithic Integration of Gallium Arsenide Optoelectronic Devices", "author": [ { "family_name": "Ury", "given_name": "Israel", "clpid": "Ury-Israel" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The optical properties of GaAs make it a very useful material for the fabrication of optical emitters and detectors. GaAs also possesses electronic properties which permit the fabrication of high speed electronic devices which are superior to conventional silicon devices. This thesis describes three examples of the monolithic integration of optical and electronic devices on semi-insulating GaAs substrates.\r\n\r\nIn the first example, an injection laser was integrated with a Gunn oscillator to yield a high frequency modulated optical source. In the second example, an injection laser was integrated with a metal semiconductor field effect transistor (MESFET). The transistor was used to modulate the current through the laser. In the third example, an integrated optical repeater was demonstrated which consisted of a MESFET optical detector, a current source, a transistor driver, and an injection laser all fabricated on a single chip. The repeater displayed an optical gain of 10 dB.\r\n\r\nIn order to facilitate the fabrication of more complex integrated optoelectronic circuits, a method was sought to form a laser cavity which did not occupy the entire width of a chip. The result was the demonstration of whispering gallery lasers which take the shape of quarter and half rings. The performance of the curved lasers was reduced from that of the straight lasers due to optical scattering at imperfections along the curve. A general theory is developed which describes mode conversion in perturbed dielectric resonators. This theory is applied to the case of the whispering gallery laser and its predictions are compared with experiment.", "doi": "10.7907/s4x6-kk53", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:4044", "collection": "thesis", "collection_id": "4044", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10122006-081036", "primary_object_url": { "basename": "Pepper_dm_1980.pdf", "content": "final", "filesize": 10933229, "license": "other", "mime_type": "application/pdf", "url": "/4044/1/Pepper_dm_1980.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Phase Conjugate Optics: On the Theory, Observation, and Utilization of Temporally-Reversed Wavefronts as Generated Via Nonlinear Optical Parametric Interactions", "author": [ { "family_name": "Pepper", "given_name": "David M.", "clpid": "Pepper-David-M" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes theoretical and experimental aspects as well as potential applications in the field of coherent optics known as Phase Conjugate Optics (PCO). By utilizing nonlinear optical techniques, real-time phase or wavefront reversal of an arbitrary incident electromagnetic field can be realized. The nonlinear optical interaction gives rise to what is referred to as the \"phase conjugate replica\" (of the incident monochromatic wave) by performing the operation of complex conjugation upon the incident wave's complex spatial amplitude in real time. This conjugate wave, which is also designated as being a \"time-reversed\" wavefront, has the property of exactly retracing the path of the incident field. The ability of the conjugate wave to correct for inhomogeneous linear and nonlinear (intensity-dependent) phase aberrations as well as polarization distortions is proved. In particular, the theory of a degenerate four-wave nonlinear optical interaction as providing for the phase conjugator is presented. The effects of linear and nonlinear losses upon this interaction are discussed. The quantum mechanical origin of the third order nonlinear optical susceptibility responsible for the four-wave mixing process is analyzed for both single and two-photon allowed transitions in an atomic (or molecular) system. The analogies of four-wave mixing with that of real-time holography are discussed. The theory of phase conjugation via four-wave mixing in optical waveguides is presented.\r\n\r\nSeveral of the above characteristics of conjugate fields are verified experimentally where phase conjugate fields via degenerate four-wave mixing were observed both in the bulk and in waveguide geometries, using carbon disulfide as the nonlinear medium. Amplified time-reversed wavefront generation as well as a mirrorless optical parametric mode of oscillation have been observed, both in agreement with theoretical predictions.\r\n\r\nPotential applications of PCO are discussed in three different regimes: spatial-frequency, temporal-frequency, and spatial/temporal frequency domains. In the first category, the ability of PCO to correct for image modal dispersion in optical waveguides as well as the use of PCO to perform real-time coherent image processing and nonlinear microscopy is discussed. Temporal-frequency domain applications of PCO to be analyzed include the use of a nearly degenerate four-wave mixing process as a narrowband, wide field-of-view optical filter, capable of an amplified bandpass. The ability of a PCO interaction to renarrow (transform limited) optical pulses which have been temporally spread due to propagation through (group velocity) dispersive channels is analyzed. A potential application of PCO in the field of nonlinear laser spectroscopy is presented. Specifically, the scattering of a probe photon off a two-photon coherent state (created in a three-level atomic system) is shown to yield a conjugate replica. This conjugate replica is capable of providing sub-Doppler width resolution of the two-photon resonance. Further, in the transient regime, the optical free-induction decay of the conjugate wave is capable of yielding detailed spectral features of the three-level system such as the anharmonic contribution to a (nearly) harmonic potential. This technique, performed in the time domain, is known as [alpha]-beat spectroscopy.\r\n\r\nFinally, a detailed theoretical and experimental study is presented of a laser resonator in which one (or both) of the mirror(s) comprising the optical cavity is replaced by a phase conjugate mirror (PCM). This novel resonator, which is termed a phase conjugate resonator (PCR), combines many of the spatial- and temporal-frequency aspects of PCO interactions discussed above. The stability criterion, transverse and longitudinal mode spectra, and the PCR output energy, as well as the frequency locking features of the laser modes to the PCM are discussed.", "doi": "10.7907/03GZ-7C28", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:17697", "collection": "thesis", "collection_id": "17697", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09232025-201049775", "primary_object_url": { "basename": "Shih_C-C_1980.pdf", "content": "final", "filesize": 51092061, "license": "other", "mime_type": "application/pdf", "url": "/17697/1/Shih_C-C_1980.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Theory of the Longitudinal Free Electron Laser. II. A Theoretical Model of the Linear Electrooptic Effect", "author": [ { "family_name": "Shih", "given_name": "Chun-Ching", "clpid": "Shih-Chun-Ching" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The first part of this work describes theoretical studies of a\r\nproposed longitudinal free electron laser. Stimulated coherent radiation\r\nin the infrared region is generated in the proposed laser by a\r\nrelativistic electron beam passing through a periodically corrugated\r\nwaveguide. The wavelength of the radiation is widely tunable by changing\r\nthe electron energy.
\r\n\r\nTheoretical investigations are based on the single-electron analysis.\r\nBoth linear and nonlinear treatments of the laser mechanism in a\r\nfree electron laser are carried out analytically. The phenomena of\r\nhomogeneous and inhomogeneous interactions, lossy gain, space-charge\r\neffect, large-signal behavior, large-gain amplification, and electron\r\ndynamics are discussed in detail.
\r\n\r\nThe second part of this work consists of a theoretical study of\r\nthe linear electrooptic effect. Application of a d.c. or low frequency\r\nelectric field to a crystal can change its electric susceptibility at\r\noptical frequencies. This effect is known as the electrooptic or\r\nPockel's effect. The semiclassical approach used is based on a one-energy\r\ngap model, dielectric theory, and the concept of bond-charge. A\r\ngeneral expression is obtained for the electrooptic coefficient of a\r\ncrystal and is applied to the calculation for diatomic and ternary compounds.\r\nThe results are generally in good agreement with the measured\r\nvalues for nearly all the crystals in which the electrooptic coefficient\r\nhad been determined.
", "doi": "10.7907/c5nd-wr34", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:11800", "collection": "thesis", "collection_id": "11800", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09242019-103435948", "primary_object_url": { "basename": "Hong_C-S_1979.pdf", "content": "final", "filesize": 51147553, "license": "other", "mime_type": "application/pdf", "url": "/11800/1/Hong_C-S_1979.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "New Optical Waveguide Devices Using Periodic and Chirped Surface Corrugations and Optical Waves in Periodic Layered Structures", "author": [ { "family_name": "Hong", "given_name": "Chi-Shain", "clpid": "Hong-Chi-Shain" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The first part of this work describes theoretical and experimental studies of some corrugated waveguide devices for use in optical communications and integrated optics. These devices include wavelength demultiplexers and broad-band optical filters using chirped corrugations, and optical scanners using the electrooptic effect in the corrugations.
\r\n\r\nThe theory of corrugated waveguides is well described by the coupled mode formalism. The problem is also treated phenomenologically by picturing the incident waveguide mode as a zig-zag ray which is diffracted by the grating surface at every bounce. Principles of the devices are given, and the parameters which characterize the devices are derived.
\r\n\r\nExperimental results on fabrication and evaluation of the devices are presented and compared with the design theory. Various techniques which have been developed during the course of this investigation are described in some detail.
\r\n\r\nThe second part of this work describes the propagation of electromagnetic waves in periodic layered structures.
\r\n\r\nA diagonalization of the unit cell translation operator of a periodic medium is used to obtain exact solutions for the Bloch waves, the dispersion relations, and the band structure of the medium. The general formalism is then applied to deal with such problems as Bragg reflectors, periodic multichannel waveguides, and electromagnetic surface waves.
\r\n", "doi": "10.7907/77TB-4N62", "publication_date": "1979", "thesis_type": "phd", "thesis_year": "1979" }, { "id": "thesis:18386", "collection": "thesis", "collection_id": "18386", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02232026-221505804", "primary_object_url": { "basename": "AuYeung_JC-W_1979.pdf", "content": "final", "filesize": 37697043, "license": "other", "mime_type": "application/pdf", "url": "/18386/1/AuYeung_JC-W_1979.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Phase Conjugate Optics and Nonlinear Optical Phenomena in Optical Fibers", "author": [ { "family_name": "Au Yeung", "given_name": "John Chen Wei", "clpid": "Au Yeung-John-Chen-Wei" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Part I of this thesis describes the theoretical and experimental\r\naspects of a new area in coherent optics known as phase conjugate optics.\r\nBy using nonlinear optical mixing techniques, the complex conjugate of an\r\narbitrary incident monochromatic wave can be generated. In particular,\r\nthe theory of the degenerate four-wave mixing technique is presented.\r\nExperimental observation of phase conjugate wave front generation in a\r\nliquid crystal material (MBBA) is described. The ability of the conjugate\r\nwave front to correct for phase aberration is demonstrated. The quantum\r\nmechanical origin of the nonlinear third order susceptibility responsible\r\nfor the four-wave mixing process is illustrated in an atomic system.\r\nBecause of a finite memory time of such an atomic system, the electromagnetic\r\nwaves taking part in the mixing process need not occur simultaneously.\r\nThe applications of the phase conjugation process to real-time\r\ninformation processing and the characteristics of a phase conjugate resonator\r\nare discussed in detail.
\r\n\r\nThe ability of an optical fiber to confine the propagation of electromagnetic\r\nwaves over a long distance and within a small cross sectional\r\narea implies that large optical intensities can be maintained over a long\r\n\" interaction length even at moderate incident optical power. Part II of\r\nthis thesis describes some third order nonlinear optical phenomena that\r\nhave been observed under this condition. Especially, phase conjugation\r\nby degenerate four-wave mixing in a fiber has been shown to require significantly\r\nless pumping power. The theoretical and experimental studies\r\nof four-wave mixing in a liquid-filled fiber are presented.
\r\n\r\nExtensive experimental efforts have been devoted over the last\r\nfew years to the study of stimulated Raman scattering and the oscillation\r\nof the Stokes radiation inside fibers. A detailed theoretical\r\ntreatment will be given here to describe these effects. The analysis\r\nshows that pump depletion due to the nonlinear process is very important\r\nin describing the stimulated Raman scattering in low loss fibers and is\r\nthe dominant saturation effect in a fiber Raman oscillator. Finally,\r\nthe implications of nonlinear optical phenomena to fiber optic communication\r\nwill be mentioned.
", "doi": "10.7907/4dcy-fx66", "publication_date": "1979", "thesis_type": "phd", "thesis_year": "1979" }, { "id": "thesis:8560", "collection": "thesis", "collection_id": "8560", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07182014-090759102", "primary_object_url": { "basename": "Lee_cp_1978.pdf", "content": "final", "filesize": 22958939, "license": "other", "mime_type": "application/pdf", "url": "/8560/1/Lee_cp_1978.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "New Optoelectronic Devices Using GaAs-GaAlAs Epitaxy", "author": [ { "family_name": "Lee", "given_name": "Chien-Ping", "clpid": "Lee-Chien-Ping" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Three subjects related to epitaxial GaAs-GaAlAs optoelectronic\r\ndevices are discussed in this thesis. They are:
\r\n\r\n1. Embedded Epitaxy
\r\n\r\nThis is a technique of selective multilayer growth of GaAs-\r\nGa1-xAlxAs single crystal structures through stripe openings in masking\r\nlayers on GaAs substrates. This technique results in prismatic layers\r\nof GaAs and Ga1-xAlxAs \"embedded\" in each other and leads to controllable\r\nuniform structures terminated by crystal faces. The dependence of the\r\ngrowth habit on the orientation of the stripe openings has been studied.\r\nRoom temperature embedded double heterostructure lasers have been\r\nfabricated using this technique. Threshold current densities as low\r\nas 1.5 KA/cm2 have been achieved.
2. Barrier Controlled PNPN Laser Diode
\r\n\r\nIt is found that the I-V characteristics of a PNPN device can be\r\ncontrolled by using potential barriers in the base regions. Based on\r\nthis principle, GaAs-GaAlAs heterostructure PNPN laser diodes have been\r\nfabricated. GaAlAs potential barriers in the bases control not only\r\nthe electrical but also the optical properties of the device. PNPN lasers\r\nwith low threshold currents and high breakover voltage have been achieved.\r\nNumerical calculations of this barrier controlled structure are presented\r\nin the ranges where the total current is below the holding point and\r\nnear the lasing threshold.
3. Injection Lasers on Semi-Insulating Substrates
\r\n\r\nGaAs-GaAlAs heterostructure lasers fabricated on semi-insulating\r\nsubstrates have been studied. Two different laser structures achieved\r\nare: (1) Crowding effect lasers, (2) Lateral injection lasers. Experimental\r\nresults and the working principles underlying the operation of\r\nthese lasers are presented. The gain induced guiding mechanism is used\r\nto explain the lasers' far field radiation patterns. It is found that\r\nZn diffusion in Ga1-xAlxAs depends on the Al content x, and that GaAs\r\ncan be used as the diffusion mask for Zn diffusion in Ga1-xAlxAs.\r\nLasers having very low threshold currents and operating in a stable\r\nsingle mode have been achieved. Because these lasers are fabricated on\r\nsemi-insulating substrates, it is possible to integrate them with\r\nother electronic devices on the same substrate. An integrated device,\r\nwhich consists of a crowding effect laser and a Gunn oscillator on\r\na common semi-insulating GaAs substrate, has been achieved.
The first part of this work describes the uses of aperiodic\r\nstructures in optics and integrated optics. In particular, devices\r\nare designed, fabricated, tested and analyzed which make use of a\r\nchirped grating corrugation on the surface of a dielectric waveguide.\r\nThese structures can be used as input-output couplers, multiplexers\r\nand demultiplexers, and broad band filters.
\r\n\r\nNext, a theoretical analysis is made of the effects of a random\r\nstatistical variation in the thicknesses of layers in a dielectric\r\nmirror on its reflectivity properties. Unlike the intentional\r\naperiodicity introduced in the chirped gratings, the aperiodicity in\r\nthe Bragg reflector mirrors is unintentional and is present to some\r\nextent in all devices made. The analysis involved in studying these\r\nproblems relies heavily on the coupled mode formalism. The results\r\nare compared with computer experiments, as well as tests of actual\r\nmirrors.
\r\n\r\nThe second part of this work describes a novel method for confining\r\nlight in the transverse direction in an injection laser. These\r\nso-called transverse Bragg reflector lasers confine light normal to\r\nthe junction plane in the active region, through reflection from an\r\nadjacent layered medium. Thus, in principle, it is possible to guide\r\nlight in a dielectric layer whose index is lower than that of the surrounding\r\nmaterial. The design, theory and testing of these diode\r\nlasers are discussed.
\r\n", "doi": "10.7907/662b-ca80", "publication_date": "1978", "thesis_type": "phd", "thesis_year": "1978" }, { "id": "thesis:10595", "collection": "thesis", "collection_id": "10595", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12072017-095000115", "primary_object_url": { "basename": "Yeh_pa_1978.pdf", "content": "final", "filesize": 72080329, "license": "other", "mime_type": "application/pdf", "url": "/10595/1/Yeh_pa_1978.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Stark-Induced Optical Nonlinearity in Gaseous NH\u2082D and Optical Waves in Layered Media", "author": [ { "family_name": "Yeh", "given_name": "Pochi Albert", "clpid": "Yeh-Pochi-Albert" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Feynman", "given_name": "Richard Phillips", "clpid": "Feynman-R-P" }, { "family_name": "Mathews", "given_name": "Jon", "clpid": "Mathews-J" }, { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The first part of this work describes theoretical and experimental\r\nstudies of Stark-induced three-wave mixing in gaseous NH2D. Application\r\nof a dc electric field to a gaseous system destroys the basic inversion\r\nsymmetry and allows two-photon mixing processes to occur. A theoretical \r\nderivation of this effect under conditions of resonantly enhanced\r\nnon-linearities is given for a three-level system. Calculations are presented\r\nfor mixing of a CO2 laser with a 4 GHz microwaves in the molecule NH2D,\r\nproducing single lower sideband radiation.
\r\n\r\nExperimental observation of resonantly enhanced, dc-induced, \r\nthree-wave mixing in gaseous NH2D is presented. The dependence of this effect\r\non gas pressure, microwave frequency, applied dc field, and microwave\r\npower are presented and compared with theoretical predictions. The\r\nexperiment was done at Hughes Research Laboratories by Abrams and his coworkers.
\r\n\r\nThe second part of this work describes the propagation of electromagnetic\r\nwaves in periodic layered media. The propagation of electromagnetic\r\nradiation in periodically stratified media is considered. Media\r\nof finite, semi-finite and infinite extent are treated. A diagonalization\r\nof the unit cell translation operator is used to obtain exact\r\nsolutions for the Bloch waves, the dispersion relations, and the band \r\nstructure of the medium.
\r\n\r\nThe theory of electromagnetic Bloch waves in periodic stratified\r\nmedia is then applied to the problems of birefringence, and group velocity\r\nin these media. The relevance of periodic media to phase matching\r\nin nonlinear mixing experiments-and to laser action in the x-ray region\r\nis discussed.
\r\n\r\nNew types of guided waves such as Bragg guided waves and optical\r\nsurface waves are theoretically predicted and experimentally observed.
", "doi": "10.7907/MBFM-X335", "publication_date": "1978", "thesis_type": "phd", "thesis_year": "1978" }, { "id": "thesis:17774", "collection": "thesis", "collection_id": "17774", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11252025-193026356", "primary_object_url": { "basename": "Yen_H-W_1976.pdf", "content": "final", "filesize": 47547025, "license": "other", "mime_type": "application/pdf", "url": "/17774/1/Yen_H-W_1976.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Gallium Arsenide-Gallium Aluminum Arsenide Distributed Feedback and Distributed Bragg Reflector Lasers", "author": [ { "family_name": "Yen", "given_name": "Huan-wun", "clpid": "Yen-Huan-wun" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This work describes theoretical and experimental studies of\r\nGaAs/GaAlAs distributed feedback and distributed Bragg reflector\r\nlasers. These lasers are strong candidates as the light source\r\nin integrated optical circuits and optical communication systems.
\r\n\r\nA coupled-mode formalism is used to study the propagation of\r\nelectromagnetic waves in a dielectric waveguide with periodic surface\r\ncorrugation. The reflection and transmission characteristics of\r\nboth passive and active periodic waveguides are found as a function\r\nof wavelength.
\r\n\r\nThese results are used to derive the oscillation conditions of\r\ntwo different laser structures: (1) the distributed feedback laser -\r\nwhere a corrugated active waveguide section is the basic structure,\r\n(2) the distributed Bragg reflector laser - where an active region is\r\nflanked by two sections of passive periodic waveguides.
\r\n\r\nThe procedure of determining the lasing wavelength is outlined.\r\nThe merits and disadvantages of various laser structures are compared\r\nand discussed.
\r\n\r\nExperimental results on fabrication and measurements of GaAs/GaAlAs\r\ndistributed feedback and distributed Bragg reflector lasers\r\nare presented and compared with the theory. Various fabrication and\r\nmeasurement techniques developed during the course of the investigation\r\nare described in some detail.
", "doi": "10.7907/vc0r-rk03", "publication_date": "1976", "thesis_type": "phd", "thesis_year": "1976" }, { "id": "thesis:8556", "collection": "thesis", "collection_id": "8556", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07172014-155953992", "primary_object_url": { "basename": "Gover_a_1976.pdf", "content": "final", "filesize": 38806350, "license": "other", "mime_type": "application/pdf", "url": "/8556/1/Gover_a_1976.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Wave Interactions in Periodic Structures and Periodic Dielectric Waveguides", "author": [ { "family_name": "Gover", "given_name": "Avraham", "clpid": "Gover-Avraham" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Pierce", "given_name": "John", "clpid": "Pierce-J" }, { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This work is concerned with a general analysis of wave interactions\r\nin periodic structures and particularly periodic thin film\r\ndielectric waveguides.
\r\n\r\nThe electromagnetic wave propagation in an asymmetric dielectric\r\nwaveguide with a periodically perturbed surface is analyzed in\r\nterms of a Floquet mode solution. First order approximate analytical\r\nexpressions for the space harmonics are obtained. The solution is\r\nused to analyze various applications: (1) phase matched second harmonic\r\ngeneration in periodically perturbed optical waveguides;\r\n(2) grating couplers and thin film filters; (3) Bragg reflection devices;\r\n(4) the calculation of the traveling wave interaction impedance\r\nfor solid state and vacuum tube optical traveling wave amplifiers\r\nwhich utilize periodic dielectric waveguides. Some of these applications\r\nare of interest in the field of integrated optics.
\r\n\r\nA special emphasis is put on the analysis of traveling wave\r\ninteraction between electrons and electromagnetic waves in various\r\noperation regimes. Interactions with a finite temperature electron\r\nbeam at the collision-dominated, collisionless, and quantum regimes\r\nare analyzed in detail assuming a one-dimensional model and longitudinal\r\ncoupling.
\r\n\r\nThe analysis is used to examine the possibility of solid state\r\ntraveling wave devices (amplifiers, modulators), and some monolithic\r\nstructures of these devices are suggested, designed to operate at the\r\nsubmillimeter-far infrared frequency regime. The estimates of\r\nattainable traveling wave interaction gain are quite low (on the order\r\nof a few inverse centimeters). However, the possibility of attaining\r\nnet gain with different materials, structures and operation condition\r\nis not ruled out.
\r\n\r\nThe developed model is used to discuss the possibility and\r\nthe theoretical limitations of high frequency (optical) operation of\r\nvacuum electron beam tube; and the relation to other electron-electromagnetic\r\nwave interaction effects (Smith-Purcell and Cerenkov\r\nradiation and the free electron laser) are pointed out. Finally, the\r\ncase where the periodic structure is the natural crystal lattice is\r\nbriefly discussed. The longitudinal component of optical space harmonics\r\nin the crystal is calculated and found to be of the order of\r\nmagnitude of the macroscopic wave, and some comments are made on the\r\npossibility of coherent bremsstrahlung and distributed feedback\r\nlasers in single crystals.
", "doi": "10.7907/V0RY-GY17", "publication_date": "1976", "thesis_type": "phd", "thesis_year": "1976" }, { "id": "thesis:3097", "collection": "thesis", "collection_id": "3097", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08112005-135414", "primary_object_url": { "basename": "Somekh_sr_1974.pdf", "content": "final", "filesize": 8280547, "license": "other", "mime_type": "application/pdf", "url": "/3097/1/Somekh_sr_1974.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Theory, Fabrication and Performance of Some Integrated Optical Devices", "author": [ { "family_name": "Somekh", "given_name": "Sasson Roger", "clpid": "Somekh-Sasson-Roger" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Recent progress in the fabrication of low attenuation optical fibers raises the attractive possibility of optical communications via these waveguides. Integration of different optical functions on one substrate in the form of optical circuits will form ideal terminals for such a communication network. We shall discuss the theory, fabrication and performance of a few \"building stones\" of such optical circuits. Optical directional couplers capable of coupling light from one channel to another will be described and their use as switches will be discussed. Distributed feedback for integrated lasers will be analyzed. Laser action in a GaAs waveguide, in which distributed feedback was supplied by corrugations fabricated on the surface, will be described. Longitudinal and transverse mode control of such a laser will also be discussed. We shall conclude with an analysis of nonlinear interactions in thin films, pointing out new methods for phase matching and ways to implement them.", "doi": "10.7907/TGHB-PR22", "publication_date": "1974", "thesis_type": "phd", "thesis_year": "1974" }, { "id": "thesis:4247", "collection": "thesis", "collection_id": "4247", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10252005-092652", "primary_object_url": { "basename": "Comly_jr_jc_1974.pdf", "content": "final", "filesize": 12753237, "license": "other", "mime_type": "application/pdf", "url": "/4247/1/Comly_jr_jc_1974.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Optical Pulse Propagation In Media Exhibiting a Third Order Nonlinear Polarization", "author": [ { "family_name": "Comly", "given_name": "Jack Clifton, Jr.", "clpid": "Comly-Jack-Clifton" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "A theoretical investigation is made of two types of distortions, self phase modulation and self-focusing, produced when an intense optical pulse propagates in a medium whose induced polarization contains terms cubic in the field strength. The first analysis indicates that the insertion of such a medium into a laser cavity can result in the generation of a train of very stable, reproducible, bandwidth-limited pulses. By using a \"circulating pulse\" model, the physical processes involved are clarified, particularly in the case of high gain in the amplifying medium. Examples are given of the Q-switched operation of such a laser, for which the pulse train differs considerably from that of conventional mode-locked systems. A second analysis deals with the steady-state self-focusing of non-axisymmetrical beams; several approaches are used to derive the increase in the threshold power for elliptical-Gaussian beam shapes. As an alternative to a fully numerical solution, a series of increasingly accurate approximate results are obtained in the form of parameterized beam functions. When an Action-Integral minimization technique is employed to optimize these parameters, the method is capable of describing the self-focusing process in some detail.", "doi": "10.7907/RW6Z-5V08", "publication_date": "1974", "thesis_type": "phd", "thesis_year": "1974" }, { "id": "thesis:14298", "collection": "thesis", "collection_id": "14298", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07082021-224732104", "type": "thesis", "title": "Proton-Implanted Optical Waveguides and Integrated Optical Detectors in Gallium Arsenide", "author": [ { "family_name": "Stoll", "given_name": "Harold McDowell", "clpid": "Stoll-Harold-McDowell" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Defect-associated energy levels which appear within the forbidden energy gap of proton-irradiated gallium arsenide give rise both to free carrier compensation and to additional near band-edge optical attenuation. These damage-induced changes in the electrical and optical properties of gallium arsenide have been exploited in the fabrication of passive optical waveguides and waveguide-compatible detectors suitable for use in integrated optical circuits. In order to understand the physical processes which underlie the operation of these structures and devices and, thereby, to suggest ways in which the irradiation and post-irradiation fabrication parameters may be optimized, a model has been constructed which explains the experimentally observed electrical and optical properties of proton-irradiated gallium arsenide. Using this model and data obtained by other investigators, a self consistent analysis of the optical confinement and attenuation properties of waveguides formed by irradiating n-type gallium arsenide with 300 keV protons has been made: Optical confinement is found to result from the so-called plasma depression effect; optical attenuation is found to be due to a combination of dissipative scattering and absorption by thermal spikes and dipole-assisted transitions between defect levels and the band continua. The model is also used to make a preliminary analysis of an integrated optical detector fabricated using the same proton-irradiation technique.
", "doi": "10.7907/m0zg-j870", "publication_date": "1974", "thesis_type": "phd", "thesis_year": "1974" }, { "id": "thesis:10689", "collection": "thesis", "collection_id": "10689", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02092018-113834352", "primary_object_url": { "basename": "Maeda_H_1973.pdf", "content": "final", "filesize": 40014878, "license": "other", "mime_type": "application/pdf", "url": "/10689/1/Maeda_H_1973.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Theoretical and Experimental Investigations of Saturation Effects in a Gas Laser", "author": [ { "family_name": "Maeda", "given_name": "Hisatoshi", "clpid": "Maeda-Hisatoshi" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Theoretical studies of standing and traveling wave lasers are\r\npresented. The spectral behavior of the amplified spontaneous emission\r\n(superradiance) in a pencil-shaped column is investigated \r\ntheoretically and experimentally. Spectral narrowing followed by rebroadening\r\nhas been observed as predicted by the theory.
\r\n\r\nA geometrical representation of an interacting two-level atomic\r\nsystem has been developed and applied to an optical laser. A semi-classical\r\nmodel for a standing wave laser has been examined using the\r\nrotating wave approximation, and compared to the exact solution.\r\nDepth and width of the Lamb dip are determined theoretically and\r\nexperimentally. The effect of radial profile of the laser field has\r\nbeen studied using the self-consistent-field approach, and the radius\r\nof the beam was measured at various positions from the window.
", "doi": "10.7907/K70K-GS53", "publication_date": "1973", "thesis_type": "phd", "thesis_year": "1973" }, { "id": "thesis:9883", "collection": "thesis", "collection_id": "9883", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06212016-105216322", "primary_object_url": { "basename": "Pearson_je_1972.pdf", "content": "final", "filesize": 39405802, "license": "other", "mime_type": "application/pdf", "url": "/9883/1/Pearson_je_1972.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Infrared Optical Parametric Fluorescence and Parametric Oscillation", "author": [ { "family_name": "Pearson", "given_name": "James Edward", "clpid": "Pearson-James-Edward" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The properties of optical parametric fluorescence and parametric oscillation are considered in detail. Parametric fluorescence occurs when a pump light source (usually a laser) is incident on a nonlinear crystal; an input pump photon is \"split\" into two new photons whose energies sum to that of the pump. The frequencies of the fluorescence output can be tuned by varying the nonlinear crystal refractive indices. In a parametric oscillator, an optical resonator is used to provide feedback at the fluorescence frequencies so that coherent oscillations occur. The result is a coherent, narrow bandwidth light source which is wavelength-tunable over thousands of angstroms.
\r\n\r\nFor use in theoretical discussions, the nonlinear equations which describe three-wave parametric interactions are derived from Maxwell's equations. The interaction equations are given in a general form which exhibits the spatial and temporal dependence of the fields. The equations are solved for the case of a steady-state, non-depleted pump, parametric amplifier.
\r\n\r\nThe power, bandwidth, and angular dependence of parametric fluorescence are theoretically discussed in detail. Experimental measurements using a 1.06\u03bc, Nd:YAG laser are in good agreement with the theory. The experiments constitute the first observation of parametric fluorescence in the infrared.
\r\n\r\nThe theoretical properties of parametric oscillators are discussed using a simple but rigorous Fabry-Perot analysis. The analysis gives the threshold and oscillation frequencies of a parametric oscillator and the results are used to provide some insights into an oscillator's bandwidth and stability. The rise time of a pulsed parametric oscillator driven by a Q,-switched pump is analyzed rigorously for the first time. The analysis gives a minimum peak pump power for oscillation which can be substantially larger than the \"cw\" threshold power.
\r\n\r\nMeasurements on a 1.06\u03bc-pumped, internal, LiNb03 parametric oscillator are presented. The threshold, bandwidth, mode spectra, tuning range, and time behavior are discussed and compared to theory. The experimental results show good qualitative agreement with theory except that the bandwidth is nearly an order of magnitude smaller than expected. Peak power conversion efficiencies of 50% are observed along with 10% average power conversion. Several suggestions are made for improving the performance of this type of parametric oscillator.
\r\n", "doi": "10.7907/HZSX-GD54", "publication_date": "1972", "thesis_type": "phd", "thesis_year": "1972" }, { "id": "thesis:1133", "collection": "thesis", "collection_id": "1133", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03262004-143412", "primary_object_url": { "basename": "Casperson_lw_1971.pdf", "content": "final", "filesize": 13739547, "license": "other", "mime_type": "application/pdf", "url": "/1133/1/Casperson_lw_1971.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Modes and Spectra of High Gain Lasers", "author": [ { "family_name": "Casperson", "given_name": "Lee Wendel", "clpid": "Casperson-Lee-Wendel" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This research has dealt with various problems related to high gain lasers including: gain and dispersion focusing of the transverse modes, mode pulling and mode splitting of the longitudinal modes, ultrashort pulse propagation, relaxation oscillations, spectral narrowing, dispersion effects on the oscillation line width, and a saturation and power formalism for high gain lasers. Most of these subjects had not been treated previously and it is found that the properties of high gain lasers may differ drastically from the properties of similar low gain lasers. Besides the theoretical treatment of these subjects, experimental verification has been obtained whenever possible. The experiments were conducted using 3.51 micron xenon lasers.", "doi": "10.7907/7JZX-4J40", "publication_date": "1971", "thesis_type": "phd", "thesis_year": "1971" }, { "id": "thesis:10847", "collection": "thesis", "collection_id": "10847", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05042018-121029705", "primary_object_url": { "basename": "Hall_DB_1971.pdf", "content": "final", "filesize": 36390313, "license": "other", "mime_type": "application/pdf", "url": "/10847/1/Hall_DB_1971.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Waveguiding and Electrooptic Modulation of Light with GaAs Epitaxial Thin Films", "author": [ { "family_name": "Hall", "given_name": "David Barnett", "clpid": "Hall-David-Barnett" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Guiding and electrooptic modulation of light at 1;15\u03bc from a HeNe laser has been achieved in a thin film semiconductor waveguide.The guide was composed of a thin (~ 10\u03bc) epitaxial film of GaAs sandwiched between a GaAs substrate and an evaporated aluminum coating.The slightly higher refractive index of the guide relative to the substrate allowed the propagation of one single optical TM mode and one single optical TM mode. Large electric fields generated in the epitaxial film by applying a voltage to the aluminum coating, induced an electrooptic change in the refractive index and a consequent modulation of the guided light.
\r\n\r\nAn important new effect, optical mode propagation cut-off, was discovered. Calculations showed that no guided modes propagated below a threshold value of the refractive index difference between guide film and substrate; above\u00b7 that value guiding occurred. This was observed when samples were switched from a non-guiding \"off\" state to a guiding \"on\" state by applying a modulation voltage that increased the refractive index of the guide, making it go through cut-off.
\r\n", "doi": "10.7907/V28G-M218", "publication_date": "1971", "thesis_type": "phd", "thesis_year": "1971" }, { "id": "thesis:10788", "collection": "thesis", "collection_id": "10788", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04042018-141845978", "primary_object_url": { "basename": "Patel_NB_1971.pdf", "content": "final", "filesize": 39984825, "license": "other", "mime_type": "application/pdf", "url": "/10788/1/Patel_NB_1971.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Electrical and Optical Characteristics of Indium Arsenide Junction Lasers", "author": [ { "family_name": "Patel", "given_name": "Navin B.", "clpid": "Patel-Navin-B" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Electrical and light emission characteristics of pulsed InAs \r\njunction lasers were studied at various temperatures ranging from \r\nliquid helium temperature to room temperature. The junctions were\r\nprepared by vapor diffusing Zn into Sn doped n-type wafers of InAs, \r\nwith a donor concentration of 1018cm-3. Data variation of\r\ncapacitance with bias showed these to be abrupt junctions. At low\r\ninjection currents, the current injection mechanism was determined\r\nto be photon-assisted tunneling. Gain and loss factors at 20.4\u00b0K \r\nwere determined from the variation of threshold current with diode \r\ncavity length. An independent value of the gain factor was determined \r\nfrom the observed variation with current of the superradiantly \r\nnarrowed line-width from a nonlasing structure.\tThe time-resolved \r\nlaser spectra shift to longer wavelengths with time during pulsed \r\noperation of the laser.\tThe line shift results from joule heating\r\nof the diode, and follows the variation of bandgap of InAs with temperature.\t\r\nMode confinement studies indicate that the mode confinement is due to the \r\noptical gain in the active region at the junction and that the active \r\nregion extends to approximately a diffusion length on both \r\nsides of the junction.\r\n", "doi": "10.7907/3EQ6-5M79", "publication_date": "1971", "thesis_type": "phd", "thesis_year": "1971" }, { "id": "thesis:10343", "collection": "thesis", "collection_id": "10343", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06262017-154848811", "primary_object_url": { "basename": "Laussade_J-P_1969.pdf", "content": "final", "filesize": 59471245, "license": "other", "mime_type": "application/pdf", "url": "/10343/1/Laussade_J-P_1969.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Mode Locking and Ultrashort Laser Pulses by a Refractive Index Nonlinearity. II. A Theoretical Study of Optical Wave Propagation Through a Random Medium and its Application to Optical Communication", "author": [ { "family_name": "Laussade", "given_name": "Jean-Pierre Raymond Henri", "clpid": "Laussade-Jean-Pierre-Raymond-Henri" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Part I. Mode Locking and Ultrashort Laser Pulses by a Refractive Index Nonlinearity
\r\n\r\nA new method for locking the longitudinal modes of a laser\r\nresonator and generating ultrashort pulses of light has been found.\r\nThe cavity modes are coupled together when a medium possessing a\r\nrefractive index nonlinearity is placed inside the cavity.
\r\n\r\n\r\nA theoretical study is presented which analyzes the mode\r\nstructure of a laser resonator containing a cell filled with an\r\nanisotropic molecular liquid. It is found that under certain conditions\r\nthe energy exchange between the modes gives rise to a mode\r\nlocked spectrum and to the attendant generation of ultrashort pulses\r\nof light (~10-11 sec for a ruby laser, ~10-12 sec for a Nd3+ glass laser).
\r\n\r\n\r\nAn experimental investigation is reported. The presence of\r\nultrashort pulses in the output of a Q-switched ruby laser is observed\r\nwhen a liquid cell containing nitrobenzene or \u03b1-chloronaphthalene is\r\nplaced inside the cavity.
\r\n\r\n\r\nPart II. A Theoretical Study of Optical Wave Propagation Through a Random Medium and its Application to Optical Communication
\r\n\r\nIn this report we are interested in a theoretical study of\r\nwave propagation in a randomly turbulent medium and the application\r\nof the results to the evaluation of optical communication systems\r\nthrough the atmospheric turbulence.
\r\n\r\nWe first derive a power series expansion solution for the\r\nwave function u(\u2192x) of a wave propagating through a medium with a\r\nrandom index of refraction. The average wave function u(\u2192x) and the\r\ncorrelation function u(\u2192x1) u*(\u2192x2) are calculated in terms of the\r\ncorrelation function of the index of refraction, the only assumption\r\nbeing that the wavelength of the wave is much smaller than the smallest\r\nsize of the turbulence. The intensity correlation function\r\nI(\u2192x1) I(\u2192x2) is investigated and recent experimental results concerning\r\nthe behavior of the intensity fluctuations are discussed.
\r\n\r\n\r\nNext, the performances of two schemes of optical communication\r\nthrough the random atmospheric turbulence are compared: (a) heterodyne\r\ndetection, (b) video communication. It is found that for long propagation\r\npaths and strong turbulences, scheme (b) is preferable to scheme\r\n(a). This is due to the cancellation of the phase fluctuations between\r\n\"reference\" and \"signal\" parts of the beam in the video communication\r\nscheme.
\r\n\r\n", "doi": "10.7907/82JD-BB21", "publication_date": "1969", "thesis_type": "phd", "thesis_year": "1969" }, { "id": "thesis:9356", "collection": "thesis", "collection_id": "9356", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01042016-150017432", "primary_object_url": { "basename": "Zoutendyk_pja_1968.pdf", "content": "final", "filesize": 23460837, "license": "other", "mime_type": "application/pdf", "url": "/9356/1/Zoutendyk_pja_1968.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Spontaneous and Stimulated Light Emission Due to Radiative Recombination in Forward Biased Lead Telluride P-N Junctions", "author": [ { "family_name": "Zoutendyk", "given_name": "Peter John Andrew", "clpid": "Zoutendyk-Peter-John-Andrew" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Since the discovery in 1962 of laser action in semiconductor diodes made from GaAs, the study of spontaneous and stimulated light emission from semiconductors has become an exciting new field of semiconductor physics and quantum electronics combined. Included in the limited number of direct-gap semiconductor materials suitable for laser action are the members of the lead salt family, i.e . PbS, PbSe and PbTe. The material used for the experiments described herein is PbTe . The semiconductor PbTe is a narrow band- gap material (Eg = 0.19 electron volt at a temperature of 4.2\u00b0K). Therefore, the radiative recombination of electron-hole pairs between the conduction and valence bands produces photons whose wavelength is in the infrared (\u03bb \u2248 6.5 microns in air).
\r\n\r\nThe p-n junction diode is a convenient device in which the spontaneous and stimulated emission of light can be achieved via current flow in the forward-bias direction. Consequently, the experimental devices consist of a group of PbTe p-n junction diodes made from p \u2013type single crystal bulk material. The p - n junctions were formed by an n-type vapor- phase diffusion perpendicular to the (100) plane, with a junction depth of approximately 75 microns. Opposite ends of the diode structure were cleaved to give parallel reflectors, thereby forming the Fabry-Perot cavity needed for a laser oscillator. Since the emission of light originates from the recombination of injected current carriers, the nature of the radiation depends on the injection mechanism.
\r\n\r\nThe total intensity of the light emitted from the PbTe diodes was observed over a current range of three to four orders of magnitude. At the low current levels, the light intensity data were correlated with data obtained on the electrical characteristics of the diodes. In the low current region (region A), the light intensity, current-voltage and capacitance-voltage data are consistent with the model for photon-assisted tunneling. As the current is increased, the light intensity data indicate the occurrence of a change in the current injection mechanism from photon-assisted tunneling (region A) to thermionic emission (region B). With the further increase of the injection level, the photon-field due to light emission in the diode builds up to the point where stimulated emission (oscillation) occurs. The threshold current at which oscillation begins marks the beginning of a region (region C) where the total light intensity increases very rapidly with the increase in current. This rapid increase in intensity is accompanied by an increase in the number of narrow-band oscillating modes. As the photon density in the cavity continues to increase with the injection level, the intensity gradually enters a region of linear dependence on current (region D), i.e. a region of constant (differential) quantum efficiency.
\r\n\r\nData obtained from measurements of the stimulated-mode light-intensity profile and the far-field diffraction pattern (both in the direction perpendicular to the junction-plane) indicate that the active region of high gain (i.e. the region where a population inversion exists) extends to approximately a diffusion length on both sides of the junction. The data also indicate that the confinement of the oscillating modes within the diode cavity is due to a variation in the real part of the dielectric constant, caused by the gain in the medium. A value of \u03c4 \u2248 10-9 second for the minority- carrier recombination lifetime (at a diode temperature of 20.4\u00b0K) is obtained from the above measurements. This value for \u03c4 is consistent with other data obtained independently for PbTe crystals.
\r\n\r\nData on the threshold current for stimulated emission (for a diode temperature of 20. 4\u00b0K) as a function of the reciprocal cavity length were obtained. These data yield a value of J\u2019th = (400 \u00b1 80) amp/cm2 for the threshold current in the limit of an infinitely long diode-cavity. A value of \u03b1 = (30 \u00b1 15) cm-1 is obtained for the total (bulk) cavity loss constant, in general agreement with independent measurements of free- carrier absorption in PbTe. In addition, the data provide a value of ns \u2248 10% for the internal spontaneous quantum efficiency. The above value for ns yields values of tb \u2248 \u03c4 \u2248 10-9 second and ts \u2248 10-8 second for the nonradiative and the spontaneous (radiative) lifetimes, respectively.
\r\n\r\nThe external quantum efficiency (nd) for stimulated emission from diode J-2 (at 20.4\u00b0 K) was calculated by using the total light intensity vs. diode current data, plus accepted values for the material parameters of the mercury- doped germanium detector used for the measurements. The resulting value is nd \u2243 10%-20% for emission from both ends of the cavity. The corresponding radiative power output (at \u03bb = 6.5 micron) is 120-240 milliwatts for a diode current of 6 amps.
\r\n", "doi": "10.7907/AK38-EQ82", "publication_date": "1968", "thesis_type": "phd", "thesis_year": "1968" } ]