In 1984 Ducharme and Feinberg1 showed that the speed of the photorefractive effect in barium titanate was not a linear function of the light intensity I but varied instead as Ix with x < 1. This sublinear dependence prevailed over 4 orders of the light intensity (0.01 W/cm2 < I < 100 W/cm2). They also showed that the exponent x increased with increasing temperature. In 1988, Mahgerefteh and Feinberg2 showed that the speed of the photorefractive effect in barium titanate obeyed the same Ix power law for pulsed illumination as well as for cw illumination, even though the peak intensities used in the pulsed case were 104 times that of the cw experiments. This result suggested that the Ix power law was valid for a range spanning 8 orders of magnitude in the light intensity.
© 1990 Optical Society of AmericaPDF Article