Thin layers of In, Cu and Se were deposited at ambient temperature by thermal evaporation onto freshly cleaned glass substrates. The films were annealed in an inert atmosphere by an Argon-ion laser operating on all green lines with the power varied from 200 mW to 1 W. The films were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX) and X-ray diffractometry (XRD). The temperature-increment of the different layers under the incident laser powers were calculated theoretically. These results were used to suggest a mechanism for the formation of the CuInSe2 compound upon annealing the stack of elemental layers. It has been found that for the present form of the stack, the formation of the ternary chalcopyrite phase of CuInSe2 takes place through the appearance of the binary phase and subsequent reaction amongst them.