Acousto-optic polarization switch with parallax compensation

We propose acousto-optic (AO) polarization switch based on a paratellurite crystal. The geometry of anisotropic interaction is chosen so as to satisfy the Bragg conditions for the two alternative light polarizations at the wavelength 785 nm. For this both the direct and reflected from crystal face acoustic waves are used. The polarization of the output light is governed by switching between one of the two alternative frequencies of a driving ultrasound signal applied to the AO cell. The device is parallax-compensated, so that the light beams with different polarizations leave the cell at the same point, with no transverse shift, and propagate along the same direction. A corresponding AO polarization switch is manufactured and its characteristics are studied experimentally. The measured contrast ratio of the device is better than 1800:1.