Birefringence and excitonic spectra of TlGaS2 crystals

The anisotropy of transmission spectra was investigated in TlGaS2 crystals. An intensive transmission line was found in samples placed between two crossed polarizers. Ground and excited states of excitons were detected in reflectivity spectra of ТlGaS2 crystals measured in Е||a and Е||b polarizations. The reflection spectra of excitons were calculated according to dispersion equations, and the main parameters of excitons and energy bands were determined in the center of the Brillouin zone. The refractive indices na and nb were estimated for Е||a and Е||b polarizations.