The Acousto-Optical Effect in Liquid Crystals Due to Anisotropic Attenuation: New Developments and Applications

We have previously demonstrated that an ultrasonic compressional wave passing through an oriented layer of nematic liquid crystal induces a molecular reorientation perpendicular to the acow tic displacement. This was shown to be related to the anisotropy of ultrasonic attenuation in the medium. Our theory predicts t hat transmission of polarized light through the LC cell varies as the fourth power of the acoustic intensity and attenuation anisotropy, and also as the tenth power of the layer thickness, for small distortions. We present the results of new measurements on various liquid crystals as a function of acoustic pressure, angle of incidence and LC thickness, in stationnary and dynamic conditions. In all cases, theoretical p redictions are closely verified. We have established that this phenomenon makes possible a new type of acousto-optical image and hologram convertor with hjgh power of resolution, set+ sitivity in the uW/cm and good response time. We present the first acoustic images and hologram taken with such a convertor which operating principles differ widely from others.