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Proceedings Paper

Low-intensity scatterering detection with commercial spectrophotometers
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Paper Abstract

The improvement in production process of high quality optics needs routinary accurate characterization of the optical properties of the sample. Whereas some commercial instruments allow accurate measurements of the transmitted and reflected light, the measurement of the scattered light very often falls below the detection level when standard attachments, like the Ulbricht integrating sphere, are used. In order to characterize scattering levels below 10-3 dedicated set ups are usually used which are quite complicate to run and often do not fit the need of a production department. In this work we present the design and test of scatterometers based on the Coblentz sphere that fit inside a Perkin-Elmer λ-900 spectrophotometer. They are aimed to the measurement of light scattering in both the transmittion and the reflection hemisphere with a detection limit in the range of 50 ppm. The Coblentz sphere is a mirror like collector of the scattered light and does not suffer of the typical limitations of the Ulbricht sphere in terms of low collecting efficiency and spectral limitation in the UV edge. As an example, LaF3 films on silica samples were first characterized with both conventional photometric techniques (specular reflectance and direct transmittance) and ellipsometry and the film thicknesses and refractive indices, as well as inhomogeneity and interface layers, were determined. The scattering data were also independently analysed by considering the vector theory of scattering and the effect on the simulated spectral TS of several power spectrum densities obtained with different hypothesis on the correlation between interfaces.

Paper Details

Date Published: 25 February 2004
PDF: 9 pages
Proc. SPIE 5250, Advances in Optical Thin Films, (25 February 2004); doi: 10.1117/12.543708
Show Author Affiliations
Enrico Masetti, ENEA (Italy)
Anna Krasilnikova, ENEA (Italy)
Jiri Bulir, Institute of Physics (Italy)
Josep Ferre-Borrul, Univ. de Barcelona (Spain)

Published in SPIE Proceedings Vol. 5250:
Advances in Optical Thin Films
Claude Amra; Norbert Kaiser; H. Angus Macleod, Editor(s)

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