Spectroscopic ellipsometer for the infrared

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A spectroscopic ellipsometer for the infrared spectral range is to be acquired. In conjunction with the ellipsometers already available, this will be used to study the optical properties, in particular the dielectric function, of materials and systems in a wide spectral range from the far infrared (0.04 eV) to the deep ultraviolet spectral range (8.50 eV). The excitations contributing to the dielectric function in the infrared spectral region, typically phonon modes, free charge carriers and also electronic transitions, will be determined by line shape analysis and investigated for their mutual influence. Of particular interest are optically anisotropic materials, especially with a monoclinic or triclinic crystal structure. Since at least two crystal axes are not orthogonal to each other, some physical quantities, such as the tensor of the dielectric function or the effective mass tensor, have non-vanishing off-diagonal elements, so that new effects can occur, such as the violation of the LO-TO rule or the formation of singular optical axes. The influence of these non-vanishing side diagonal elements on the optical response of (bulk) materials and also artificial photonic systems as well as the underlying physical processes will be investigated. This will be done first of all by experimental determination of the dielectric tensor and complementary by fitting to theoretical line shape models as well as more general theories of optically anisotropic systems.