Determination of the Paratellurite Stiffness Constants Temperature Coefficients by the Acousto-Optic Method

Abstract

Acousto-optic (AO) phase matching condition is determined not only by the optical and acoustic waves propagation direction and parameters, but also by the physical characteristics of the AO interaction medium. Wherein, these characteristics, mainly the acoustic wave velocity, are temperature dependent. The change of ultrasound velocity relies on the medium stiffness constants cij variation with temperature. However, even for the most popular AO material – tellurium dioxide, the values of the stiffness constants temperature coefficients, given in various papers, vary significantly. The experimentally observed AO phase matching frequency temperature shift values do not coincide with those evaluated with literature data. In order to eliminate the observed discrepancy between theory and experiment, the AO phase matching frequency temperature dependencies for several AO cells based on TeO2 crystals with cut angles varying from 1.8° to 19° from the [110] axis in the (1‾10) plane were analyzed. The ultrasound velocity variation temperature coefficients were evaluated and the c11-c12 and c44 temperature coefficients that define the slow acoustic mode velocity in the selected plane were determined.