The optical spectra of silicon are studied ellipsometrically at temperatures between 300 and 1200 K in the spectral range from 2 to 4.3 eV. We present a database of optical constants for pure and heavily doped samples, with the highest concentration of free carriers of 4ϫ10 20 cm Ϫ3 . We cover the photon energy range between 0.2 and 2 eV by using an oscillator representation of the visible and ultraviolet ellipsometric data. We also report the results for the temperature dependence of the E 1 interband transition. The values of the energy shift and Lorentzian broadening of this spectral feature are obtained from analytical critical-point line shapes by fitting differentiated dielectric functions; alternatively, we apply the numerical convolution with Lorentzian contours to describe quantitatively the increased broadening with increasing temperature.

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The optical response of uniaxial SrLaA104 (SLA) and SrLaAlo.75Gao.2504 (SLAG) single crystals is investigated by several techniquesellipsometry, reflectance, and transmittance. The optical ronstants in the UV-VIS region have been obtained from the reflectance arid transmittance spectra. A novel method of measurements of the birefringence by spectroscopic ellipsometry is reported. The resulting refractive indices for both polarizations are compared with precise standard measurements performed using a single wavelength null ellipsometer. The reflectivity of SrLaA104 crystals is obtained for both polarizations in the infrared region. The fit of the spectra in terms of Lorentzian oscillators provides a quantitative comparison of the phonon mode parameters with that of LaA103, and reveals a strong anisotropy of the lattice vibrations polarized along the optical axis and perpendicular to it. Die optisch eina.chsigen Kristalle SrLaA104 und SrLaAlo 75Gao 2 5 0 4 wurden mit verschiedenen Methoden uritersucht -Ellipsometrie, Reflexion und Transmission. Aus der Kombination von Reflexions-und Transrnissionsdaten wurde der komplexe Brechungsindex im CV-VIS-Gebiet bestirrimt . Die Doppelbrechung ergab sich mit Hilfe einer neuen Methode aus spektralen ellipsometrischen Messungen in Transmission. Die resiiltierenden Brechungsindizes fur den ordentlichen und auaerordentlichen Strahl sind in guter Ubereinstimmung rriit den sehr genau aus einer Null-Ellipsometrie bei fester Wellenlange bestimmten. IR-Reflexionsspektren konnten fiir beide Polarisationsrichtimgen mit Lorentz-Oszillatoren angepaBt werden. Es zeigt sich eine ausgepragte Anisotropie auch der Gitterschwingungen.

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