Acoustic properties of LNM crystal

We report linear acoustic and acousto-optical properties of LiNa₅Mo₉O₃₀ (LNM) single crystal. This relatively new crystal, known for its complex crystallographic structure, is optically biaxial with high birefringence of 0.2545 at 450.2 nm, and crystals that consist of molybdates are widely used in different applications, from cintillators, double β-decay detectors, "dark matter" sensors to electro optics. The lowest measured propagation velocity of shear wave was 1200 m/s, and for the longitudinal mode it was 4100 m/s, which are a relatively low value for crystalline media. The maximum attenuation of the longitudinal wave at a frequency of 180 MHz was moderate and equal 20 dB/cm·GHz². The values of the acousto-optic figure of merit for light diffraction on a longitudinal acoustic wave were also determined, the maximum value of the coefficient was 13 c.u., which exceeds the efficiency of the one used in AO devices material α-SiO₂. Thus, the set of measured acoustic and elastic-optical properties shows a new promising optically biaxial material for acousto-optics, which needs for further researching. (paper)