High quality tellurium dioxide for acousto-optic and non-linear applications

Abstract

Paratellurite, TeO2, was first grown by the Czochralski method by Arlt and Schweppe (1) and has been shown to have an appreciable figure of merit for acousto-optic applications (2). We have studied improved methods for growing high quality TeO2 and have investigated its usefulness as a nonlinear optic material. Our studies show that the quality of tellurium dioxide single crystals as well as their physical properties and ease of growth are dependent on the purity of the starting material. Careful preparation of crystals by the Czochralski technique (5) from melts of six nines pure material has produced paratellurite with acoustooptic properties superior to those previously reported (2). The acoustic loss of such material when measured at 100 megacycles is reduced by approximately an order of magnitude. The useful acousto-optic figure of merit, M3, (7) was found to be ~3.4 times better than PbMoO4, previously the best material for device applications below 1 Ghz. Thus, high quality TeO2 is now of interest for Q-switch and deflector applications. We have also found TeO2 to have a nonlinear coefficient ~2 times that of quartz and to be phase matchable at 1.06μ as well as 1.3μ The fact that this effect is in direct violation of Kleinman's symmetry conditions, which dictate a coefficient of zero for the reported structure, will be discussed along with a detailed procedure for the growth of high quality crystals.