Observation of two-beam coupling in semi-insulating GaN with electroabsorption effect

Most of semi-insulating compound semiconductors show photorefractive effect. Its photorefractive response is quite fast compared with paraelectric and ferroelectric crystals, or organic materials. Sometimes the effect is enhanced by the band edge effect such as the electroabsorption. However, photorefractive effect has not been reported in nitride semiconductors, which are intensely studied as promising nonlinear optical materials for the blue and ultra-violet wavelength region. In this paper, we report the observation of the photorefractive two-beam coupling in semi-insulating GaN thin crystal.