Investigation Of The Microscopic Parameters Governing The Photorefractive Effect In KTa_(1-x)Nb_xO_3: Cu,V

Abstract

We perform a microscopic analysis of the photorefractive effect in KTa_(1-x)Nb_xO_3: Cu,V. We have independently measured all relevant parameters which enter into the Kukhtarev model of the photorefractive effect. Cu is found to be the partially filled donor level responsible for the photorefractive effect. The total Cu concentration was determined from electron microprobe analysis to be 1.8(1 0^19)cm%3. A series of oxidation and reduction treatments were used to alter the concentration of Cu^(1+) and Cu^(2+). The concentration of Cu in each valence state after each heat treatment was determined using the relative magnitudes of the Cu^(1+) charge transfer band and the Cu^(2+) crystal field transition. The electron photoexcitation cross section at 514nm was determined to be 9.08(10^-20)cm^2 . The ratio of the mobility to electron recombination rate was determined from photoconductivity measurements to be 6.20(10^8) 1 /(v-cm).