Instationary conjugate optical-thermal fields in thin films due to pulsed laser heating: A comparison between back and front treatment

Manufacturing of multilayer thin films deposited on a glass substrate can be accomplished by means of pulsed laser sources. Thermal and optical nonlinearities are induced during transient heating, since the response of weakly absorbing thin films depends on the temperature. The heat source can either directly impinge the film surface,␣front treatment, or the glass substrate, back treatment. In this paper a one-dimensional conjugate non-linear thermal-optical time dependent problem is numerically analysed. The investigation is accomplished in order to compare the two processes. For a Nd-YAG laser with wavelength of 1064 nm, a a-Si/TCO and Al/a-Si/TCO multilayers are investigated. Results are presented in form of spatial and temporal temperature profiles as well as absorbed heat transfer rates inside the layers. The accomplished analysis clearly shows that the back treatment is more efficient in terms of manufacturing process, oriented to the production of photovoltaic cells. Received on 4 November 1997