High photorefractive sensitivity at 860 nm in reduced rhodium-doped KNbO3

We show that high-temperature reduction in a CO-CO2 atmosphere increases the photorefractive sensitivity of KNbO3:Rh at 860 nm by 3 orders of magnitude compared with that of the as-grown crystal. The effective trap density is increased by a factor of 3, and the photoconductivity by a factor of 30, and the photorefractive response at a grating spacing of 0.15 mu m is accelerated by a factor of 400. The grating buildup time at a grating spacing of 0.7 mu m and an intensity of 1 W cm(-2) is 0.5 a, a value comparable with that of as-grown The optical and photorefractive parameters of Rh-doped KNbO3 subjected to reduction treatment are characterized for wavelengths of 0.48-1.064 mu m. (C) 1997 Optical Society of America.