Beam coupling in undoped GaAs at 1.06 microm using the photorefractive effect.

We have observed beam coupling and degenerate four-wave mixing in high-resistivity, undoped GaAs at 1.06 microm that is due to the photorefractive effect. The photorefractive species is thought to be the deep donor EL2. The measured values of two-wave gain are comparable with those measured in Bi(12)SiO(20). The response time is measured to be 20 microsec at an intensity of 4 W/cm(2). This exceptionally fast photorefractive response time (compared with that of oxide electro-optic materials) is due primarily to the large mobility of GaAs.