We report the complex refractive index of methylammonium lead iodide (CH 3 NH 3 PbI 3) perovskite thin films obtained by means of variable angle spectroscopic ellipsometry and transmittance/reflectance spectrophotometry in the wavelength range of 190 nm to 2500 nm. Film thickness and roughness layer thickness are determined by minimizing a global unbiased estimator in the region where the spectrophotometry and ellipsometry spectra overlap. We then determine the optical bandgap and Urbach energy from the absorption coefficient, by means of a fundamental absorption model based on band fluctuations in direct semiconductors. This model merges both the Urbach tail and the absorption edge regions in a single equation. In this way, we increase the fitting region and extend the conventional (α ω) 2-plot method to obtain accurate bandgap values.

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We have investigated the effect of doping on absorption for various SiC polytypes, i.e., n-type (N) 6H–SiC, 4H–SiC, and 15R–SiC, p-type (Al) 6H–SiC, and 4H–SiC, and p-type (B) 6H–SiC. For these polytypes the band-gap narrowing with higher doping concentration is observed. In addition, for n-type doping below band-gap absorption bands at 464 nm for 4H–SiC, at 623 nm for 6H–SiC, and at 422 and 734 nm for 15R–SiC are observed. The peak intensities of these absorption bands show a linear relation to the charge carrier concentration obtained from Hall measurements. The corresponding calibration factors are given. As an application a purely optical wafer mapping of the spatial variation of the charge carrier concentration is demonstrated.

We report theoretical calculations and experimental observations of Pancharatnam's phase originating from arbitrary SU (2) transformations applied to polarization states of light. We have implemented polarimetric and interferometric methods which allow us to cover the full Poincaré sphere. As a distinctive feature, our interferometric array is robust against mechanical and thermal disturbances, showing that the polarimetric method is not inherently superior to the interferometric one, as previously assumed. Our strategy effectively amounts to feed an interferometer with two copropagating beams that are orthogonally polarized with respect to each other. It can be applied to different types of standard arrays, like a Michelson, a Sagnac, or a Mach-Zehnder interferometer. We exhibit the versatility of our arrangement by performing measurements of Pancharatnam's phases and fringe visibilities that closely fit the theoretical predictions. Our approach can be easily extended to deal with mixed states and to study decoherence effects.

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