准同型相界附近的弛豫铁电单晶体具有较大的压电效应，因而得到了广泛地研究。一般而言，具有较大铁弹响应的材料也具有较高的声光效应。尤其是大的晶格参数变化和应力所致相变可以同时产生大的折射率变化，二者可以同时提高声光效应。本文在马赫-曾德尔干涉光路中对晶体样品施加单轴应力，测量得到了0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (0.65PMN-0.35PT)单晶的声光系数π。研究结果表明，该单晶表现出了极高的声光系数，例如，π33达到了15.2×10-12 m2/N。这些研究结果表明，弛豫铁电单晶是激光束偏转器和声光调制器的优选材料。

Relaxor ferroelectric single crystals were intensively investigated due to large piezoelectric effects near the morphotropic phase boundary (MPB). In general, materials with large ferroelastic responses may also have high acousto-optic effects. Especially, both large lattice parameter changes and stress induced phase transition can bring large refractive index changes, which enhances the overall acousto-optic effects. The acousto-optic coefficients π were characterized for 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (0.65PMN-0.35PT) single crystal under uniaxial stress using Mach-Zender interferometer method. The results show that the crystal exhibits very high acousto-optic values, for example, π33 can reach 15.2×10-12 m2/N, indicating that relaxor ferroelectric single crystals are promising candidates for laser deflectors or acousto-optic modulators.