Spatial and temporal properties of a continuous-wave phase-conjugate resonator based on the photorefractive crystal BaTiO_3

We report measurements on spatial and temporal properties of a cw phase-conjugate resonator (PCR) based on the photorefractive crystal BaTiO(3) and pumped with millwatt power levels from a He-Ne or a Kr(+)-ion laser. In the absence of an intracavity aperture, the output beam is observed to be elongated in the direction of the crystal c axis by means of preferential self-defocusing of the beam by the highly anisotropic photorefractive effect in BaTiO(3). When the coherence length of the pump laser is much smaller than the round-trip distance in the PCR, the time constants for buildup and decay of the PCR power are found to be much larger than those of the photorefractive response.