Phenomenological theory of dynamical light scattering from dielectric bulk waves in semi-infinite opaque crystals

Abstract

A recently established phenomenological theory of dynamical light scattering from coupled systems of acoustical lattice waves and free-carrier-density waves in unbounded opaque semiconductors has been extended to semi-infinite crystals. On the basis of a quasistatic two-wave interference approximation, expressions have been obtained for the noncollinear real and imaginary parts of the wave vectors of the forward-diffracted optical eigenmodes. The frequency dispersion of the modes, the opacity broadening of the linewidths, the boundary kinematics, and the reflectance have been analyzed. With main emphasis on the plasma dispersion relation in the long-wavelength limit, the basic concepts have been applied to a study of dynamical diffraction from acoustoelectrically bunched conduction electrons in $n$-InSb at 80 K. Numerical results based on a Boltzmann-equation calculation of the free-carrier bunching are presented. A particular analysis is given of the anomalous transmission in the collision-dominated regime ($\mathrm{Ql}\ll 1$) of acoustoelectric interaction assuming the electron gas to be collisionless ($\omega \tau \gg 1$) in regard to its optical properties.