Abstract

Optically active uniaxial crystals like paratellurite (TeO₂) are widely used as interaction media in acoustooptic devices. Paratellurite finds its most important application in low frequency deflectors that utilize the [110] propagating slow shear wave. Optical activity plays a significant role in the behavior of such devices. In this paper acoustooptic deflector configurations in optically active media with arbitrary interaction planes are investigated by using an exact formulation. Attention is focused on the so-called optically rotated configuration, where the optical axis is offset from the interaction plane. The acoustic frequency at which tangential phase matching occurs, and the associated Bragg angles, are solved analytically as a function of the offset angle. Exact expressions are derived for polarizations of incident and diffracted beams, as well as for the effective acoustooptic figure of merit. A formulation is presented that describes the behavior of phased array Bragg cells in uniaxial crystals. This formulation demonstrates for the first time that wideband deflection around a desired center frequency can be obtained while having freedom of choice regarding the acoustic mode and interaction plane. The design of phased array deflectors in optically active paratellurite which utilizes the [110] propagating slow shear wave is discussed. It is shown that the birefringent phased array design has distinct advantages over the more conventional optically rotated or acoustically rotated configurations.

© 1989 Optical Society of America