Photorefractive effect in GaP

Abstract
The photorefractive effect in undoped semi-insulating GaP was observed. GaP has a photorefractive sensitivity in the spectral region of 0.6 to 0.9 μm. The photorefractive center is the deep donor resulting from the P antisite defect. We measured the two-beam coupling gain coefficient and its time constant as functions of the grating period and the pumping intensity, using a 633-nm He–Ne laser. The maximum gain coefficient of 0.33 cm−1 was obtained at a grating period of 1.1 μm. The time constant, which depends on the grating period, was 3–20 msec at a pumping intensity of 30 mW/cm2.