Quasi-Steady State Numerical Model for a Multilayer Thin Film Irradiated by a Moving Laser Source at High Peclet Numbers

A numerical analysis of the conjugate optical-thermal fields in an amorphous silicon thin film deposited on a glass substrate and irradiated by a moving Gaussian laser source is carried out. The velocity of the laser is assumed constant and quasi-steady state conditions are considered. Optical and thermophysical properties of materials are assumed temperature dependent. The conjugate optical and thermal models are solved by means of a finite volume numerical technique and the heat conduction along the direction of motion has been neglected. The optical field is considered locally one-dimensional and it has been solved by means of the matrix method. Results are given in terms of radiative coefficients, absorption function distribution and temperature profiles and fields. The effect of the relative velocity and of the thin film depth are analyzed. For the considered model, radiative coefficients profiles show that for the largest thin film thickness, reflectance values do not depend very much on the Peclet number and on the x coordinate. Temperature profiles point out that the maximum temperature values are attained for an intermediate thin film thickness among the three considered values. This is due to the interference effects within the thin film that cause the maximum energy absorption for this thickness.