Abstract <p>The current investigation focuses on examining the fundamental optical parameters of thin films with a thickness of ~500 nm, composed of quaternary glassy materials GeTe_{(2 –} _<i>x</i>)(SeSb)_<i>x</i> (<i>x</i> = 0, 0.2, 0.4, 0.6). This includes describing the optical absorption data using Tauc’s relationship, evaluating the extinction coefficient and refractive index, and consulting the correlation between optical band gap and refractive index. Additionally, the research explores the one essential oscillator dispersal parameters, dielectric properties, and certain non-linear optical constants. Spectrophotometric measurements of transmittance (<i>T</i>) and reflectance (<i>R</i>) are employed to study the dielectric and optical properties of the film samples. The extinction coefficient (<i>k</i>) and Optical refractive index (<i>n</i>) are utilized to approximate various critical opto-electrical and dielectric parameters. The results show an increase in parameter values including normal refractive index, static refractive index, single oscillator energy, lattice dielectric constant, high frequency dielectric constant, charge carrier concentration, volumetric energy loss functions and third order susceptibility. The investigated optical properties conclude that the material is useful for optical data storage applications.</p>