26 June 2017 Dielectric function parameterization by penalized splines
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In this article, we investigate the penalized spline (P-spline) approach to restrict flexibility of dielectric function parameterization by B-splines and prevent overfitting of the ellipsometric data. The penalty degree is easily controlled by a certain smoothing parameter. The P-spline approach offers a number of advantages over well-established B-spline parameterization. First of all, it typically uses an equidistant knot arrangement which simplifies the construction of the roughness penalties and makes it computationally efficient. Since P-splines possess the “power of the penalty” property, a selection of the number of knots is no longer crucial, as long as there is a minimum knot number to capture all significant spatial variability of the data curves. We demonstrate the proposed approach by real-data application with ellipsometric spectra from aluminum-coated sample.
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Dmitriy V. Likhachev, "Dielectric function parameterization by penalized splines", Proc. SPIE 10330, Modeling Aspects in Optical Metrology VI, 103301J (26 June 2017); doi: 10.1117/12.2270259; https://doi.org/10.1117/12.2270259

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