Near-infrared four-wave mixing with gain and self-starting oscillators with photorefractive GaAs

We report high-reflectivity four-wave mixing in photorefractive GaAs:Cr crystals at 1.06 microm using a nearly degenerate interaction with an externally applied dc electric field (moving-grating recording mode). The highest reflectivities (R approximately 5) are observed for the positive-readout configuration with cross-polarized pump beams. The variation in reflectivity with the pump-beam ratio is presented for two pump-beam polarization states and compared with theory. Self-starting optical resonators are also described.