Abstract

The temperature-dependent photorefractive properties of cubic insulators such as Bi₁₂SiO₂₀ (BSO) and semi-insulators such as GaAs:Cr and InP:Fe are well documented but poorly understood. As crystal temperatures are raised above room temperature, photorefractive efficiencies tend to increase and the photorefractive response times decrease. This phenomenon has been attributed to a temperature dependency of various photorefractive parameters such as the crystal conductivity, carrier mobility, defect capture cross section, and transmission grating depth. We have made above-room temperature measurements on two types of BSO: Materia) with the characteristic absorption edge at 500 nm grown by the traditional Czochralski process and material grown by a hydrothermal transport process that is missing this characteristic edge. The hydrothermal absorption edge is at 400-nm, which we believe represents the band-to-band absorption for BSO. Undoped hydrothermal material is not photorefractive. Low temperature, thermally stimulated current (TSC) analysis of the hydrothermal material shows it contains 3-4 orders of magnitude fewer deep level defects than, the Czochralski material. The above-room temperature electrical characteristics of the two materials are, however, quite similar. Both contain what appears to be a 1.1 eV thermally activated conductivity that evidently has no effect on the photorefractive properties of the materials.

© 1993 Optical Society of America