STUDIES ON FORMATION MECHANISMS OF SELF-PUMPED PHASE-CONJUGATION IN BATIO3-CE CRYSTALS AT WAVELENGTHS FROM 570 TO 680 NM

Formation mechanisms of self-pumped phase conjugation (SPPC) in two Ba TiO3:Ce crystals with different doping concentrations have been experi mentally studied. The pump beam was from dye lasers, with an overall t unable wavelength region lying between 570 and 680 nm. Variations of t he optical beam path patterns as well as reflectivity of the phase con jugators with respect to the incident angle, the incident position, an d the wavelength of the pump were investigated in two configurations. One configuration corresponds to that in which the pump enters an a fa ce of the crystal; the other to that in which the pump enters the +c f ace of the crystal. It was found that SPPC is sometimes established in a way similar to that of a cat phase conjugator, but usually without the formation of a clear beam path loop. Sometimes SPPC is established by a stimulated photorefractive backscattering and four-wave mixing m echanism. In these cases, however, the crystal corners as well as the scattering centers on the crystal faces usually play an important role by seeding the stimulated photorefractive backscattering processes. I n other cases SPPC is established by both the cat and the stimulated p hotorefractive backscattering and four-wave mixing mechanisms.