Spectroscopic ellipsometry measurements were conducted to determine optical constants of CdSexTe1-x  (CST) compounds deposited through co-evaporation, with the composition parameter (x) ranging from 0 to 1. The dielectric function spectra obtained from these thin films were interpolated using an energy-shift algorithm to develop a comprehensive optical library for the CST compound with x ranging from 0 to 1 with a 0.001 step.