Phase-modulated spectroscopic ellipsometry and polarized transmission intensity studies of wide-gap biaxial CaGa2S4

Differently prepared natural (100)-oriented cleavage planes of the orthorhombic wide-gap (Eo∼4.1 eV) single crystalline CaGa2S4 were examined in two symmetric positions at room temperature over the photon energies 0.8-6.5 eV by spectroscopic ellipsometry. Complimentary, polarized transmission intensity technique was applied. The data obtained by both techniques were further treated within standard biaxial approach and the major refraction indices were restored for the practically important range below energy gap. The structure and polarization peculiarities of the obtained pseudo-dielectric function were related with apparently four critical points of interband electronic transitions in ZZ (E1=4.49 eV, E3=5.34 eV) and YY (E2=5.00 eV, E4=6.21 eV) configurations, respectively