Temperature dependence of the dynamic response of the photorefractive signal in Bi12SiO20

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Abstract
The dynamic response of the photorefractive signal in Bi12SiO20 with no external electric field was studied as a function of temperature. At low temperatures, the response follows the predicted exponential behavior. At temperatures higher than 220 °C with the writing beams on, the signal increases to a peak intensity and decays with time, with a time constant that varies with temperature. When the write beams are turned off and no erasure beam is present, the signal exhibits a sharp decrease and then increases to a secondary maximum before the final decay occurs. When an erasure beam is present, the same general signal pattern is observed but the secondary peak can be significantly greater at high temperatures. The theory of Kukhtarev satisfactorily describes the signal patterns observed at low temperatures. The more complex signal patterns observed at high temperatures are explained by postulating the presence of mobile positive charges which compensate the electric fields established by the negative charges participating in the photorefractive response of the material.