Influence of Bi content on linear and nonlinear optical properties of As40Se60-xBix chalcogenide thin films

The manuscript reports the effect of Bi content on the linear and nonlinear optical properties as well as the structural and physical properties in thermally evaporated As(40)Se(60)(-x)Bi(x )chalcogenide thin films. The optical properties of the as-deposited films have been studied from the optical transmission data recorded by UV-Visible spectrometer. The linear optical parameters (linear refractive index n, extinction coefficient k, absorption coefficient alpha), indirect optical band gap, Urbach energy, oscillator energy, dispersion energy were calculated from the transmission data which were strongly influenced by Bi content. The dispersion of refractive index was analyzed in terms of single oscillator Wemple-Di Domenico model. The third order nonlinear susceptibility (chi((3))) and nonlinear refractive index (n(2)) were calculated from the linear parameters using semi-empirical relations. The optical gap decreased which was discussed by chemical bond approach and degree of disorder possessed by the films. The optical properties changes in the films were also well supported by the Raman shift. The structural characterization by X-ray diffraction revealed the amorphous nature of the prepared films whereas the composition and micro structure of the studied films were probed by energy dispersive X-ray analysis and field emission scanning electron microscopy study.