PHASE CONJUGATION BY STIMULATED PHOTOREFRACTIVE SCATTERING USING A RETROREFLECTED SEEDING BEAM

The threshold for self-pumped optical phase conjugation by means of backward stimulated photorefractive scattering has been dramatically lowered by inserting a retroreflecting screen into the path of the beam after the beam leaves a BaTiO3 crystal. Stable reflectivities of as much as approximately 60% and good phase-conjugate fidelity have been demonstrated in a crystal that has too low a gain-length product to exhibit unseeded backward stimulated scattering. Precise control of the threshold for stimulated scattering is demonstrated by adjusting the seed intensity. Reflectivity and fidelity are experimentally characterized at 515 nm as a function of the following parameters: pump and seed intensities, crystal angle with respect to the incident beam direction, crystal interaction length, crystal-lens separation, and aberration strength. Operation at 633, 730-800, and 839 nm is demonstrated also.