A spatial Fourier transform approach is proposed to investigate the polarization changing and the beam profile deformation of light during the acousto-optic (AO) interaction in isotropic media. Two basic types of sound waves are considered, namely, longitudinal and shear waves interacting with the light in an AO bulk cell. The perturbation of the permittivity is then caused by these kinds of acoustic waves and can be expressed in tensor forms. The evolution of two different orders of scattered light under the Bragg condition can be properly described by a couple of solutions that are derived from the wave equation by using a spatial Fourier transform approach. The solutions explicitly comprise the effects of polarization changing, beam deformation, and propagational diffraction. It is shown that the spatial beam profiles of the scattered light are distorted during the process because of the effects of the AO interaction and the propagational diffraction. For both cases of longitudinal and shear sound waves, the degree of the profile deformation can be controlled by changing the amplitude and the frequency of the sound. It is also shown that the polarization states of the scattered light are different from those of the input light on account of the AO effect. The degree of difference of the polarization states, which depend on the propagation type, frequency, and amplitude of the sound wave, can be examined through the use of two polarization parameters, the ellipticity and the orientation of the major axis of the scattered light. Detailed numerical simulations, including Fourier-transforming the incident light profile to calculate the spectra and the on-axis values of ellipticity and orientation of the scattered light in space with use of the inverse Fourier transform, are presented.
© 1997 Optical Society of America
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