Phase conjugate interactions by photorefractive BaTiO3
Phase conjugate interactions by photorefractive BaTiO3
The properties of photorefractive phase conjugate mirror configurations are investigated. It is shown that, for certain input geometries, the generally used experimental configuration for the `cat mirror' Self-Pumped Phase Conjugate Mirror in BaTiO3, in which the input beam is extraordinary polarised, does not provide the optimum phase conjugate reflectivity. The inclusion of a small ordinary polarised component in the input can as much as double the phase conjugate reflectivity, and allows the phase conjugate output power to be controlled with net gain. The observed enhancement is attributed to the erasure of competing parasitic gratings by the ordinary polarised component. Input beam intensity dependent effects have previously been observed in photorefractive wave mixing interactions. Here the observation of total input intensity dependent reflectivity from Mutually Pumped Phase Conjugator configurations is reported. This has allowed the investigation of optical switching and thresholding. The origin of these effects is attributed to competition between Mutually Pumped Phase Conjugation and the cat mirror Self-Pumped Phase Conjugator, resulting from different exponents in their intensity dependent response times. The use of a third input beam to Mutually Pumped Phase Conjugators is investigated, allowing optical switching to be performed. The observation of dynamic instabilities in the phase conjugate output from the Bird-Wing Phase Conjugator is reported, and a phenomenological model, based upon beam configurations present within the crystal during a typical oscillation cycle, is developed. The instabilities are attributed to competition between the Bird-Wing Phase Conjugator and Self-Pumped Phase Conjugation. The properties of phase conjugate mirror formed by degenerate four wave mixing in BaTiO3 are investigated, and the effects which these properties have on the performance of a phase conjugate resonator in which this phase conjugate mirror acts as the gain medium are discussed. Finally a scheme is presented which uses cascaded two-beam coupling interactions to optically generate a logarithmic transform. Optimisation of the two free parameters of gain coefficient and beam intensity ratio produces an output intensity which is the natural logarithm of the input intensity with an accuracy better than 1% over a four decade dynamic range.
University of Southampton
1991
James, Stephen Wayne
(1991)
Phase conjugate interactions by photorefractive BaTiO3.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The properties of photorefractive phase conjugate mirror configurations are investigated. It is shown that, for certain input geometries, the generally used experimental configuration for the `cat mirror' Self-Pumped Phase Conjugate Mirror in BaTiO3, in which the input beam is extraordinary polarised, does not provide the optimum phase conjugate reflectivity. The inclusion of a small ordinary polarised component in the input can as much as double the phase conjugate reflectivity, and allows the phase conjugate output power to be controlled with net gain. The observed enhancement is attributed to the erasure of competing parasitic gratings by the ordinary polarised component. Input beam intensity dependent effects have previously been observed in photorefractive wave mixing interactions. Here the observation of total input intensity dependent reflectivity from Mutually Pumped Phase Conjugator configurations is reported. This has allowed the investigation of optical switching and thresholding. The origin of these effects is attributed to competition between Mutually Pumped Phase Conjugation and the cat mirror Self-Pumped Phase Conjugator, resulting from different exponents in their intensity dependent response times. The use of a third input beam to Mutually Pumped Phase Conjugators is investigated, allowing optical switching to be performed. The observation of dynamic instabilities in the phase conjugate output from the Bird-Wing Phase Conjugator is reported, and a phenomenological model, based upon beam configurations present within the crystal during a typical oscillation cycle, is developed. The instabilities are attributed to competition between the Bird-Wing Phase Conjugator and Self-Pumped Phase Conjugation. The properties of phase conjugate mirror formed by degenerate four wave mixing in BaTiO3 are investigated, and the effects which these properties have on the performance of a phase conjugate resonator in which this phase conjugate mirror acts as the gain medium are discussed. Finally a scheme is presented which uses cascaded two-beam coupling interactions to optically generate a logarithmic transform. Optimisation of the two free parameters of gain coefficient and beam intensity ratio produces an output intensity which is the natural logarithm of the input intensity with an accuracy better than 1% over a four decade dynamic range.
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Published date: 1991
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Local EPrints ID: 461044
URI: http://eprints.soton.ac.uk/id/eprint/461044
PURE UUID: 08d7de44-a178-445e-b624-b755704d19da
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Date deposited: 04 Jul 2022 18:34
Last modified: 04 Jul 2022 18:34
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Author:
Stephen Wayne James
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