Acoustic and elastic anisotropy of acousto-optic Pb₂P₂Se₆ crystals

We have determined experimentally the acoustic wave velocities for Pb₂P₂Se₆ crystals and obtained complete matrices of the elastic stiffness and elastic compliance coefficients on this basis. The anisotropy of the acoustic wave velocities has been analyzed, and the spatial directions of propagation and polarization of the slowest acoustic waves have been determined. In the case of acousto-optic (AO) interaction with these waves, the AO figure of merit can reach extremely high values, thus making Pb₂P₂Se₆ a promising AO material for the infrared spectral range.