Numerical model for back treatment of multilayer thin films by a moving laser source

A two-dimensional non stationary analysis of the conjugate optical-thermal fields induced in a multilayer thin film structure on a glass substrate by a moving Gaussian laser source is carried out numerically in order to study laser back treatment processes. The work-piece is considered semi-infinite along the motion direction and different thicknesses of the thin film are considered. Thermal and optical non-linearities are induced during transient heating, since the response of weakly absorbing thin films depends on temperature. The heat source impinges on the back surface of the glass substrate. The optical field is assumed to be locally one-dimensional and Maxwell equations are solved in order to evaluate the energy absorption in the thin films; the thermal field is assumed to be two-dimensional. COMSOL Multiphysics 3.4 code was employed to solve the conjugate thermal and electromagnetic problem Transient temperature profiles and temperature fields for different Peclet numbers and amorphous silicon thicknesses are presented.