  Photoluminescence and polarized reflection spectra of quantum well structures
with symmetric Cd$_{0.9}$Zn$_{0.1}$Te/CdTe/Cd$_{0.9}$Zn$_{0.1}$Te and
asymmetric Cd$_{0.9}$Zn$_{0.1}$Te/CdTe/Cd$_{0.4}$Mg$_{0.6}$Te barriers were
studied. The Stokes parameters of the reflected light from these structures
were measured. In the structures with symmetric barriers, exciton resonances
were found in the reflection spectra and were not present in the
photoluminescence spectra. In structures with asymmetric barriers, in the
region of exciton resonances, the phenomenon of light birefringence was
detected, caused by a lower symmetry of the interfaces compared to the symmetry
of bulk crystals. A discussion of both phenomena was given.
