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Analysis of laser-assisted chemical etching processes of a pinhole by monitoring diffraction patterns of reflected beams.

The detailed processes of laser-assisted chemical etching are studied by using an optical in situ monitoring method. Various Al thin-film specimens are processed in aqueous H(3)PO(4) solutions by shining focused Ar(+) laser beams. As etching progresses, it is observed in the backreflected laser beam that a concentric circular fringe pattern appears and shrinks. The development of the etching process is explained by analyzing the diffraction patterns with an etched shape function of a Gaussian nature.