Optical Properties of Ge_23.5Pb₂₀S_56.5 Glassy System

Abstract

The spectra of refractive index and absorption coefficient in thin films of Ge23.5Pb20S56.5 glassy system were calculated on the base of analysis of transmission spectra. The refractive index has values between 2.0 and 2.6 in the spectral range between 500 nm and 1200 nm. The existence of indirect allowed transitions with energy Eg = 1.70 ± 0.01 eV and phonon energy of wph= 0.11 eV at room temperature was found. For values of the absorption coefficient a < 103см –1 the fundamental absorption edge is described by exponential function known as Urbach-rule. The static structure disorder parameter wo, is equal to 0.06 eV.