Experimental determination of full matrices of the piezo-optic and elasto-optic coefficients for Pb₅Ge₃O₁₁ crystals

We determine full matrices of piezo-optic and elasto-optic coefficients for lead germanate crystals, Pb₅Ge₃O₁₁, using Dixon-Cohen and interferometric methods. Two different types of samples are studied, single- and multi-domain. We show that the correct data for the Pb₅Ge₃O₁₁ crystals can be obtained only with single-domain samples, since the domain structure induces a number of features that make the final results unreliable. We demonstrate that the acousto-optic figures of merit reach high-enough values at the isotropic acousto-optic interactions with longitudinal acoustic waves propagating along the principal x and z axes (63×10^-15 and 37×10^-15s³/kg), respectively. At the same time, the efficiency of the acousto-optic interactions with transverse acoustic waves is low. The same is true concerning anisotropic acousto-optic diffraction, since the appropriate elasto-optic coefficients are small enough.