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Angle resolved scattering: An effective method for characterizing thin film coatings

: Schröder, S.; Herffurth, T.; Blaschke, H.; Duparre, A.


Applied optics 50 (2011), No.9, pp.C164-C171
ISSN: 0003-6935
ISSN: 1539-4522
ISSN: 1559-128X
Journal Article
Fraunhofer IOF ()

Light scattered from interface imperfections carries valuable information about its origins. For single surfaces, light-scattering techniques have become a powerful tool for the characterization of surface roughness. For thin-film coatings, however, solving the inverse scattering problem seemed to be impossible because of the large number of parameters involved. A simplified model is presented that introduces two parameters: Parameter delta describes optical thickness deviations from the perfect design, and parameter beta describes the roughness evolution inside the coating according to a power law. The new method is used to investigate structural and alteration effects of HR coatings for 193 nm, as well as laser-induced degradation effects in Rugate filters for 355 nm.