Investigation of anomalous acoustooptic interaction in lithium niobate crystal

Abstract

Expressions are derived for the calculation of the central frequencies f ⁰_1,2 , and the frequency band δf of wide-band anomalous acoustooptic interaction in crystals of arbitrary symmetry class. The effect of the difference between the ray and phase velocities of the diffracted light on the magnitude of f ⁰_1,2 and δf is pointed out. Results are presented of the computed acoustooptic quality factor M₂, the frequencies f ⁰_1,2 , δf and the electromechanical coupling constant for the tangential field k_D for cuts of LiNbO₃ crystals ensuring maximum diffraction efficiency. It is shown that the maximum M₂=22.10⁻¹⁸ cgs units in this crystal is attained in the case of anomalous light diffraction by the slow shear wave propagating in the Y-120‡ direction. To the same cut there corresponds the maximum K_D=0.685. The design of anomalous acoustooptic deflectors developed is described. Experimental results are presented.