LIGHT DIFFRACTION BY ULTRASONIC WAVES AS A MULTIPLE SCATTERING PROCESS.
LOCKHEED MISSILES AND SPACE CO SUNNYVALE CALIF
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The phenomenon of light diffraction by ultrasonic waves has been studied extensively in the past, but quantitative investigations have been limited in scope, probably because of computational difficulties. Recently, there has been developed a method of analysis that allows numerical computation for arbitrarily specified conditions to be carried out on a digital computer. This method, which employs approximate theory and an iterative process, is used in this study to investigate the ultrasonic diffraction effect over a wide range of conditions. When the ratio of light wavelength to ultrasonic wavelength is small compared to unity, the theoretical development on which this numerical analysis is based shows that the intensities in the various diffraction orders are determined by three nondimensional parameters. These parameters are related to three physical parameters of the ultrasonic beam-wavelength, intensity, and width-and two physical parameters of the light beam-wavelength and incidence angle. Special attention is given to the variation of diffracted-beam intensity with variation of the parameters about values that produce strong Bragg scattering into the -1st order. These conditions are of particular interest because of the possibility of diverting all incident-beam power into one diffraction order under control of the ultrasonic beam. In addition, the conditions required for strong Bragg diffraction into the -2nd order are determined. Author