Birefringence in the transparency region of GaAs/AlAs multiple quantum wells

Birefringence measurements for in-plane propagation of light below the absorption edge in GaAs/AlAs multiple quantum wells ~MQW’s! are reported for different well/barrier widths. A remarkable drop in the low-frequency limit of the birefringence has been observed for MQW structures with small periods and ascribed to the presence of local fields. The temperature dependence of the birefringence is also studied and complementary results in InP quantum dot structures are also presented. The latter exhibit a strong resonant birefringence, which can be explained by the reduced dimensionality in the joint density of states for optical transitions in the dots. @S0163-1829~99!00635-9#