Aspects of thermally induced nonlinearities in the index of refraction are investigated for the case of degenerate four-wave mixing (DFWM). An expression for the reflectivity is derived within the framework of a coupled thermodynamic–electromagnetic theory, and some implications for the conjugation efficiency are briefly discussed. We also report on experimental measurements of phase-conjugate reflectivities in excess of 200% at 532 nm and comment on the role of saturation effects and pump delays in obtaining the observed efficiencies. Finally, the results of near-field conjugation beam-quality studies are presented with a view toward examining some of the parameters crucial to conjugation fidelity in typical DFWM experimental setups.
© 1983 Optical Society of America
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