Photoelasticity and acousto-optic diffraction in piezoelectric semiconductors

Abstract

Contributions from the free-carrier screened indirect photoelastic effect and from the free-carrier density fluctuations to the photoelasticity in piezoelectric semiconductors have been considered by taking account of the existence of both electrons and holes. Explicit expressions for the effective photoelastic constants corresponding to these contributions have been derived on the basis of the small-signal acousto-electric theory. The results obtained are applicable either to extrinsic or to intrinsic semiconductors. The numerical evaluation of these contributions has been carried out by taking tellurium as an example. In accordance with the theoretical prediction, an appreciable diffraction ascribable to the free-carrier density fluctuations has been observed in the acousto-optic diffraction experiments.