The intermediate regime of light diffraction by ultrasound in planar gyrotropic optical waveguides in an external electric field

A theoretical investigation is carried out for an intermediate regime of optoacoustic interaction, close to the Bragg one, by ultasonic Rayleigh surface waves in gyrotropic planar waveguides in an external electric field. A system of equations of associated waves is presented which describes the planar optoacoustic interaction in intermediate, Raman—Nath, and Bragg regimes of diffraction by ultrasonic surface waves in gyrotropic crystals with electrically induced anisotropy. It is shown that the intermediate (transition) regime of optoacoustic interaction, which is characterized by an angular selectivity and by the presence of several diffraction maxima, is the basic regime of diffraction. In this case diffracted light is generally elliptically polarized with an ellipticity and polarization azimuth that depend on the external electric field intensity. Translated from Zhurrnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 30–35, January–February, 1999.