LINEAR TERMS IN (Q)OVER-RIGHT-ARROW IN THE MACROSCOPIC OPTICAL-PROPERTIES DF ZINCBLENDE TYPE MATERIALS - THEORY AND EXPERIMENT

Situations under which off-diagonal symmetric or antisymmetric terms i n the dielectric tenser epsilon(ij)(omega, q ($) over bar) of zincblen de-type materials, proportional to the wavevector of the light q ($) o ver bar; may exist are reviewed and clarified. Off-diagonal linear ter ms in q ($) over bar have been associated with macroscopic effects on the polarization of the light of two different kinds: optical activity (antisymmetric) and gyrotropic birefringence (symmetric). Contrary to recent reports concerning GaAs, we show that gyrotropic birefringence caused by the symmetric off-diagonal linear terms in the dielectric t ensor does not exist in bulk crystals under equilibrium conditions. An y such reported effects should be attributed to residual internal stre ss or surface effects.