Theory of light scattering by longitudinal-acoustic phonons in superlattices

Abstract

We study the scattering of light by longitudinal-acoustic phonons propagating along the axis of an infinite superlattice. In contrast to previous works, we take into account not only the difference between the acoustic and photoelastic parameters of the two media, but also the difference between their refractive indexes. In this case the incident and scattered light in the superlattice are represented by Bloch waves instead of plane waves. The scattering intensities, calculated in closed form by using a transfer-matrix method, are then valid for any value of the scattering wave vector q and not limited to q values small compared with the size of the Brillouin zone, \ensuremath{\pi}/D. The peak intensities are discussed for GaAs-AlAs superlattices as functions of the composition, period, and photoelastic parameters. The results may show noticeable differences with those of the previous works, especially for q near the boundaries of the successive Brillouin zones.