Abstract
The photorefractive effect was observed in Fe-doped semi-insulating GaN. We measured the two-beam coupling constant and the grating formation time as a function of pump intensity at a wavelength of 458nm in reflection geometry. The photorefractive gain coefficient was 0.39cm−1, and the grating formation time was 7ms at a pump intensity of 1.0W/cm2. Besides the refractive index grating, the contribution of an absorption grating was also observed in a two-wave mixing experiment. The coupling constant of the absorption grating was negative and increased with the pump intensity. The origin of the absorption grating was attributed to light-intensity-dependent photochromism.
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