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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenWed, 31 Jan 2024 19:02:26 +0000Nonlinear and Anisotropic Effects in Magnetically Tuned Laser Amplifiers
https://resolver.caltech.edu/CaltechTHESIS:03302017-091624259
Authors: {'items': [{'id': 'Dienes-Andrew', 'name': {'family': 'Dienes', 'given': 'Andrew'}}]}
Year: 1967
DOI: 10.7907/AF03-T980
<p>Using semiclassical radiation theory and a density matrix
formalism we analyze the nonlinear characteristics of a gas laser
amplifier operating with two optical frequency signals of arbitrary
polarization and having an axial magnetic field. Both perturbational
solutions, valid for relatively weak intensities and solutions valid
for arbitrarily strong fields are obtained for two nonlinear effects:
the saturation interaction of the electromagnetic waves, and the
generation of combination tones. An arbitrary amount of Doppler
broadening is considered throughout.</p>
<p>The detailed treatment of J = 1 to J = 0 model yields the
frequency, magnetic field and polarization dependence of the nonlinear
effects. The results are presented analytically and graphically
and are discussed using physical arguments. It is found that only
saturation but no combination tone generation occurs for two opposite
circularly polarized input signals while both are, in general, present
for two arbitrary linearly or elliptically polarized fields. For
two opposite circular waves the interaction is found to comprise three
parts, each with a different behavior: self saturation, common level
mutual saturation and a coherent double quantum interaction. The
total interaction (coupling) between the two fields is always weak.
The limiting case of a single linearly polarized field is considered
separately, the zero magnetic field "dip" and the nonlinear behavior
of the Faraday rotation is discussed.</p>
<p>For two linearly (or elliptically) polarized waves the three
nonlinear processes listed above take place between opposite circular
components. In addition a modulation of the population inversion
densities occurs due to the presence of two different frequencies with
the same circular polarization. This results in the generation of new
frequencies and also contributes to the coupling between the input
fields. The coupling depends on the magnetic field, and on the frequency
separation and the polarization states of the signals. The
limiting case of zero magnetic field is examined. It is found that the
medium is made effectively anisotropic by the nonlinear interactions.
The polarization vectors of two linearly polarized fields rotate apart
unless the angle between them is zero or 90 degrees.</p>
<p>The results are extended to the general J<sub>a</sub> to J<sub>b</sub> transition.
In zero magnetic field the nonlinear effects are found to depend on
ΔJ, while for nonzero magnetic field resonances in the interaction
occur whenever the frequency difference between two opposite circularly
polarized transitions that have common level equals the frequency
separation of the input fields. Combination tone generation takes
place for all but two opposite circularly polarized signals.</p> https://thesis.library.caltech.edu/id/eprint/10120