Polarized transmission intensity studies at and below energy gap of wide-gap single crystalline CaGa2S4 Original Research Article

Polarized transmission intensity studies have been performed on wide-gap single crystalline CaGa2S4 at room temperature. The effective value of the partial birefringence in (100) plane is determined to be comparatively large varying from 0.14 to 0.50 with increasing photon energy from 1.9 to 3.5 eV. Four structures, which were preliminary ascribed to the critical points of interband optical transitions are displayed by ellipsometric examination with the aid of a spectroscopic phase-modulated ellipsometer in the spectral range 1.5–6.3 eV. These points, together with band gap singularity, are believed to largely contribute into the optical properties below the energy gap of biaxial CaGa2S4. The pseudo values of two major components of dielectric function tensor of CaGa2S4 are given for the first time.