title: Conditions for anomalous acousto-optical diffraction by backward propagating acoustic waves.
abstract: Experimental evidence is given of acoustic plate waves, whose group velocity is contradirected with respect to the phase velocity, through a determination of the acoustic wavelength dependence on frequency, in a limited range of frequencies. The dependence dLambda/dOmega>0 between wavelength and frequency is experimentally verified, as the required condition for acousto-optical diffraction, where higher frequency components would scatter light into smaller diffraction angles.
authors: Department of Energetics, Rome University "La Sapienza" and Istituto Nazionale di Fisica della Materia, Sezione di Roma I, 00161 Rome, Italy.
authors: A
authors: A
authors: Alippi
authors: A
authors: A
authors: Bettucci
authors: M
authors: M
authors: Germano