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

Birefringence measurements for in-plane propagation of light below the abso rption edge in GaAs/AlAs multiple quantum wells (MQW's) are reported for di fferent well/barrier widths. A remarkable drop in the low-frequency limit o f the birefringence has been observed for MQW structures with small periods and ascribed to the presence of local fields. The temperature dependence o f the birefringence is also studied and complementary results in InP quantu m dot structures are also presented. The latter exhibit a strong resonant b irefringence, which can be explained by the reduced dimensionality in the j oint density of states for optical transitions in the dots.