Coupled wave equations for acousto-optic diffraction of a divergent light beam in absorbing medium
Theory of acousto-optic (AO) diffraction of a long wavelength radiation have to take into account divergence of a light beam upon propagation. The effect of a light beam divergence is especially strong in terahertz (THz) range. In this spectral range the most suitable AO media are absorbing and it's light absorption coefficient is about 1 1/cm. Theory of AO interaction taking into account divergence of a light beam and a medium absorbance is developed and coupled wave equations are derived.