OPTICAL ANISOTROPY IN GAAS ALXGA1-XAS MULTIPLE-QUANTUM WELLS UNDER THERMALLY-INDUCED UNIAXIAL STRAIN/

The effect of thermally induced in-plane uniaxial strain on the optica l properties of a GaAs/AlxGa1-xAs multiple quantum well (MQW) has been studied in detail. The strain was produced by bonding the MQW thin fi lms to LiTaO3, a transparent substrate which possesses a direction-dep endent thermal expansion coefficient. At temperatures different from t he bonding temperature we have observed an anisotropy in the optical p roperties of the MQW due to the strain-induced lowering of its in-plan e fourfold rotation symmetry. The anisotropic absorption and birefring ence for light incident normal to such a MQW structure have been deter mined and compared to a theory involving the mixing of the valence sub bands.