Large Nonlinearities in Four-Wave Mixing in Photorefractive Crystals and Applications in Passive Optical Phase Conjugation.

This thesis describes the development of several passive phase conjugate mirrors (PPCM's) based on four -wave-mixing in photorefractive crystals such as BaTiO(,s) and Sr(,1-x)Ba(,x)Nb(,2)O(,6). They function over the entire visible spectrum and have been observed to yield phase conjugate reflectivities of the order of 30%. The strongly nonlinear optical interactions involved in these devices give rise to many intricate effects including bistability and a new phenomenon known as double phase conjugation. A theory of four-wave-mixing in photorefractive crystals is developed and solved without using the undepleted pumps approximation. The operation thresholds and phase conjugate reflectivities of the various devices are derived, and many of their peculiar behaviors can be explained. Experimental demonstrations of the new devices include tests of their phase conjugate imaging capabilities and the use of one of the PPCM's as an end mirror of an argon ion laser to correct for intracavity distortions.