Kilometer scale interferometers for the detection of gravitational waves are currently under construction by the LIGO (Laser Interferometer Gravitational-wave Observatory) and VIRGO projects. These interferometers will consist of two Fabry-Perot cavities illuminated by a laser beam which is split in half by a beam splitter. A recycling mirror between the laser and the beam splitter will reflect the light returning from the beam splitter towards the laser back into the interferometer. The positions of the optical components in these interferometers must be controlled to a small fraction of a wavelength of the laser light. Schemes to extract signals necessary to control these optical components have been developed and demonstrated on the tabletop. In the large scale gravitational wave detectors the optical components must be suspended from vibration isolation platforms to achieve the necessary isolation from seismic motion. These suspended components present a new class of problems in controlling the interferometer, but also provide more exacting test of interferometer signal and noise models.
\r\n\r\nThis thesis discusses the first operation of a suspended-mass Fabry-Perot-Michelson\r\ninterferometer, in which signals carried by the optically recombined beams are used to\r\ndetect and control all important mirror displacements. This interferometer uses an optical\r\nconfiguration and signal extraction scheme that is planned for the full scale LIGO interferometers with the simplification of the removal of the recycling mirror. A theoretical analysis of the performance that is expected from such an interferometer is presented and the experimental results are shown to be in generally good agreement.
", "doi": "10.7907/y4w8-tn94", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "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" } ]