The graphical-analytical method was used to find the solution of the inverse problem in ellipsometry for the system consisting of a transparent single-layer dielectric film on the Cd<sub>1-x</sub>Mn<sub>x</sub>Te crystal substrate. The nomograms in the φ-Δ ellipsometric coordinates were simulated to determine the refractive index of the film and its thickness for different incidence angles of the laser beam with 632.8 nm wavelength. The treatment of the Cd<sub>1-x</sub>Mn<sub>x</sub>Te (х=0.1-0.4) thin films and crystal surfaces was carried out with the millisecond (τ=1.5 ms) and nanosecond (τ=80 ns) laser. The structuralphase transformations of the films and layers in the Cd-Mn-Te system were studied in the AFM and SEM, and their ellipsometric characteristics were determined using photometric laser ellipsometer. The heterogeneity of the thickness and structure of the laser-modified Cd<sub>1-x</sub>Mn<sub>x</sub>Te surface layers were analyzed using calculated distribution of the refractive index of the films and its dependence on the incidence angle of the laser beam.