Thin films of As₄₀S_60-xSe_x ((0 ≤ x ≥ 60) at. %) have been efficiently synthesized through the process of vacuum thermal evaporation. The present framework analyzes the thin films to determine both optical and electronic parameters as a function of change of Se concentrations. The thickness of the obtained films, d have been mathematically determined utilizing Swanepoel's computations and experimentally via an MII-4 interference microscope with an accuracy of 1%. The thickness of the studied films has been closed to 500 ± 15 nm. Additionally, the optical properties of these films have been scrutinized from the transmittance and reflectance spectra measured by a UV–Vis–NIR spectrophotometer. The transmission spectra, T (λ) of such films have been documented in the spectral region 400–2500 nm. Based on the optical measurements, all of the linear optical constants, the linear optical and dielectric parameters, the linear and non-linear optical susceptibility criteria, and the material dispersion coefficient M(λ) have been computed. Besides, the nonlinear refractive index, energies of the electronic polarization have been determined.