The role of dysprosium ions as a dopant on linear and nonlinear optical dispersion parameters in a-Se thin film

Thin films of un-doped and doped a-Se with Dysprosium rare-earth ions have been prepared by the thermal evaporation technique. The optical transmission spectra of the investigated films have been measured in a wide spectral range and used to calculate the linear optical constants together with the optical energy gap of studied films. The observed decrease in the values of the energy gap against the increase of the Dysprosium (Dy) content in a-Se films has been explained using Mott and Davis Model and in terms of electronegativity difference of the constituent atoms. Furthermore, the dispersion of nonlinear parameters such as second-order refractive index and nonlinear absorption coefficient (two-photon absorption coefficient) of investigated films are presented and discussed.