Laser-induced thermal strains in isotropic media: Polycrystalline Si

Analytic solutions for the spatial distribution of elastic deformations, strains, and stresses induced on the surface and interior of an isotropic semi-infinite material by an arbitrary temperature distribution are applied to an isotropic medium which is exposed to an intense cw laser beam. We demonstrate results of such calculations in the case of polycrystalline silicon. The method can be applied to any polycrystalline material, or even moderately anisotropic cubic crystals. The calculations show the presence of considerable amounts of thermal strains or stresses for laser power densities below melting.