We have been successful in procuring commercial semi-insulator grade GaAs crystals from Sumitomo that exhibit in our laboratory a gain coefficient of 6.4 cm(-1), a phase-conjugate beam reflectivity of 6, and a grating build-up time of less than 10 ms at a wavelength of 1.06 mu m. Electrical and optical properties of these crystals in two- and four-wave-mixing experiments are described for both de electric field and moving-grating biases on the crystal. Oscillator experiments have also been performed with a retromodulator as the retroreflective mirror in the feedback loop of the resonator cavity. (C) 1997 Optical Society of America.