Anisotropic diffraction of acoustic waves in crystals used in acousto-optic dispersive delay lines

Acoustooptic (AO) light dispersive delay lines (LDDL) are widely used in high-power ultrashort laser pulse amplification chains for pulse shaping. The geometry of AO interaction of LDDL is determined mainly by the acoustic beam propagation and photoelastic properties of the crystal. Propagation of bulk acoustic wave (BAW) beams depends on acoustic anisotropy of the crystal and is characterized by the planar tensor of diffraction, which can be considered as an extension of anisotropy parameter for 3D-space. Two nonzero eigenvalues of the tensor are compared for pure shear BAWs propagating in the symmetry planes of TeO₂ and LiNbO₃. The found combinations of BAW characteristics, including high velocity, low diffraction, and sufficiently large acousto-optic figure of merit, make lithium niobate more preferable for application in LDDL with rapid scan repetition frequency up to 100 kHz compared to TeO₂.