Acousto-optic properties of tellurium that are useful in anisotropic diffraction

The acoustic, optical and acousto-optic (AO) properties of tellurium crystals are examined here with the objective of developing AO devices in this crystal that operate in the 4-8 mu m infrared region. Detailed analysis of anisotropic diffraction of light that is characterized by a change in the optical mode is carried out. The phase velocities of acoustic waves in three basic planes of the material, the directions of elastic polarization, and acoustic walkoff angles are calculated. Magnitudes of the AO figure of merit M-2 in the crystal are evaluated to obtain optimum AO interaction geometries. Our results show that the slow shear elastic waves propagating in XZ and Y Z planes of the crystal may offer the best AO interaction geometry applicable to AO deflectors and imaging filters, and predict a maximum value of M2 in tellurium to be 160 x 10(-12) s(3) kg(-1). Measurement results for optical and AO parameters of tellurium are also included.