PHOTOTHERMAL DEFORMATION WITH PULSED EXCITATION.

Abstract

Theoretical and experimental results are presented for the near-field surface deformation of solids produced by laser pulses of about 20-ns duration, at fluences below the ablation threshold. The theoretical model applies rigorous thermoelastic theory for an isotropic solid to an infinite plate of finite thickness, using Laplace and Hankel transform techniques with numerical inversion to minimize simplifying assumptions. The theoretical results identify, and the experimental data confirm, three regimes in the temporal behavior of the near-field surface deformation: 1) local thermal expansion during the pulse, followed by 2) deformation due to propagating surface and bulk elastic pulses, followed or accompanied by 3) quasi-static plate motion, i. e. , gross motion of the plate in response to the thermal stresses.