Investigation of the microscopic parameters governing the photorefractive effect in KTa_1-xNb_xO₃:Cu,V

Summary form only given. A microscopic analysis of the photorefractive effect in KTa_1-x Nb_x0₃:Cu,V (KTN) is discussed. All relevant parameters which enter into the Kukhtarev model of the photorefractive effect were independently measured. 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(10¹⁹) cm^-3. A series of oxidation and reduction treatments was used to alter the concentration of Cu¹⁺ and Cu²⁺. The concentration of Cu in each valence state after each heat treatment was determined using the relative magnitudes of the Cu¹⁺ charge transfer band and the Cu²⁺ crystal field transition. The electron photoexcitation cross section at 514 nm 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(10⁸) 1/(V-cm). The analysis permits determination of the oxygen partial pressure and temperature necessary to control the Cu valence states and hence photorefractive properties of the KTN sample. It is thus possible to vary and control the magnitude and response time for a given application.