Specific directions of ultrasound propagation in double potassium tungstates for light modulation

Acousto-optical characteristics of double potassium tungstates are analyzed and specific directions for light modulation are found. First, an important subgroup of elasto-optic coefficients of KYb(WO₄)₂ and KLu(WO₄)₂ crystals are calculated with use of experimental data. It is revealed that with proper choice of ultrasound direction the acousto-optical figure-of-merit approximately 2 times exceeds the maximum value detected in previous experiments. Another unique direction is determined, which permits modulation of randomly polarized light. The elasto-optic characteristics of KYb(WO₄)₂ and KLu(WO₄)₂ crystals are compared to those of previously investigated materials of the same crystal group: KY(WO₄)₂, KGd(WO₄)₂.