Piezo-, elasto- and acousto-optic properties of Tl₃AsS₄ crystals

Complete matrices of piezo-optic and elasto-optic tensors are experimentally determined for Tl₃AsS₄ crystals. It is revealed that the piezo-optic coefficients are very high, ∼10^-11  N/m² in the order of magnitude. This implies that Tl₃AsS₄ can be referred to the best piezo-optic materials. The same concerns the elasto-optic coefficients, of which absolute values are in the interval 0.28-0.54. It is also found that, at the anisotropic and isotropic interactions with the slowest transverse and longitudinal acoustic waves, the acousto-optic figure of merit reaches extremely high values (1.99×10^-12  s³/kg and 9.45×10^-13  s³/kg, respectively). In other words, the Tl₃AsS₄ crystals can be referred to as one of the best acousto-optic materials for the visible and infrared spectral ranges.