Our observations of Bi2SiO20 show that refractive-index gratings can decay under uniform illumination at two separats rates. This paper presents calculations based on a model of photorefractivity with two photoactive levels that provides a natural explanation of the two-time constant grating decay. In these calculations the usual conduction or valence band model of a single-species photorefractive material1 is. generalized to include a second species of traps in which the charge carriers can recombine.
© 1983 Optical Society of AmericaPDF Article