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TECHNICAL PAPERS

Laser-Induced Deformation Patterns in Thin Films and Surfaces

[+] Author and Article Information
Daniel Walgraef

Center for Nonlinear Phenomena and Complex Systems, Free University of Brussels, CP 231, Bd du Triomphe, B-1050 Brussels, Belgium

J. Eng. Mater. Technol 121(2), 182-188 (Apr 01, 1999) (7 pages) doi:10.1115/1.2812365 History: Received August 06, 1998; Revised October 22, 1998; Online November 27, 2007

Abstract

The coupling between surface deformation and defect motion may be at the origin of deformation patterns in thin films under laser irradiation. We analyze the dynamics of laser-induced vacancy densities and deformation fields and show how it triggers deformational instabilities, in the case of uniform and focused laser irradiation. Pattern selection analysis is performed, through linear, nonlinear, and numerical methods. In irradiation with extended beams, we show that, according to the relative importance of nonlinearities arising from the defect or from the bending dynamics, square, hexagonal or even quasi-periodic patterns are selected. It appears, furthermore, that one-dimensional gratings are always unstable in isotropic systems. In irradiation with focused laser beams, rose deformation patterns, with petal number increasing with laser intensity, naturally arise in this model, in qualitative agreement with experimental observations. These results claim for more systematic and quantitative experimental investigations of deformational pattern formation under laser irradiation.

Copyright © 1999 by The American Society of Mechanical Engineers
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