Ellipsometric studies in the energy range 1.5–5 eV have been performed on thin films of Cd1−xMnxTe deposited by sublimation from alloys prepared by melt quenching. The spectra showE0,E1, andE1+&Dgr;1transitions of cubic semiconductors. The changes in peak positions under influence of HeNe laser light, small alternating magnetic field, and under the influence of both applied simultaneously have been investigated. Shifts in peak positions observed for all the three transitions have been interpreted on the basis of changes in the band structure of Cd1−xMnxTe thin films at these critical points. This has been corroborated by theoretically calculating the effective number of electrons contributing to transition per atomNeffand the density‐of‐states data. ©1995 American Institute of Physics.