Chalcogenide thin films finds extensive applications in optical imaging, optical recording, integrated optics, optical communications and microelectronics. Optical constants (absorption coefficient, refractive index and extinction coefficient) of amorphous, thermally annealed and laser irradiated Ga15Se85 and Ga15Se83In2 thin films deposited by thermal evaporation onto chemically cleaned glass substrate, were calculated from absorbance and reflectance spectra as a function of photon energy in the wavelength region 400-900 nm. Analysis of the optical absorption data shows that the rule of non-direct transitions predominates. It has been found that the absorption coefficient increasing with increasing the exposure time of laser irradiation and also by increasing photon energy. The optical band gap decreases with increasing annealing temperatures. The refractive index (n) decreases, while the extinction coefficient (k) increases with increasing annealing temperature. The laser irradiated thin films showed a decrease in optical band gap and absorption coefficient with increasing exposure time of laser irradiation. The values of refractive index (n) increases and extinction coefficient (k) decreases with increasing exposure time of laser irradiation. The results have been analyzed on the bases of thermal annealing and laser irradiation effects in the chalcogenide thin films. (C) 2010 Elsevier B.V. All rights reserved.