22 June 2013 Precision heterodyne ellipsometry with an improved conic fitting algorithm
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Proceedings Volume 8769, International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN2013); 87692F (2013) https://doi.org/10.1117/12.2019043
Event: International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN2013), 2013, Singapore, Singapore
Abstract
Ellipsometers based on heterodyne interferometers are inherently capable of precise measurements, with the ellipsometric angles determined from the amplitude and phase of a pair of quadrature signals. These signals are generally displayed as a Lissajous figure and the primary limitation to accuracy is determined by the goodness-of-fit to the ellipse, especially for ellipses with high ellipticity. In this paper we describe an improvement to the ellipse­ fitting algorithm of Halir & Flusser. A Michelson interferometer was constructed and a polarizer-quarterwave plate combination used to generate ellipses of moderate to extreme ellipticity. We show experimentally that our method yields excellent fits, even for axis ratios approaching 300: 1, yielding a one-sigma error of 0.5 mrad (less than λ/10000) in the presence of measurement noise.
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Lionel R. Watkins, Lionel R. Watkins, Matthew J. Collett, Matthew J. Collett, } "Precision heterodyne ellipsometry with an improved conic fitting algorithm", Proc. SPIE 8769, International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN2013), 87692F (22 June 2013); doi: 10.1117/12.2019043; https://doi.org/10.1117/12.2019043
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