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The refractive index of GaAs has been measured in the wavelength range from 0.97 to 17 um, which covers nearly the entire transmission range of the material. Also, accurate values are predicted for QPM conditions in which extremely large parametric gain bandwidths can be obtained.

An automatic infrared ellipsometer for the study of surface and interface phenomena has been constructed. The system is based on a Fourier transform spectrometer that we equipped with an ellipsometer unit. Polarizers and analyzers are of the ion-etched wire-grid type. Their rotation is governed by means of a computer-controlled stepping-motor system. A discussion of calibration procedures for the infrared range is given, and special attention is given to the problem of selecting the best measurement strategy. The polarization state of the reflected beam is determined by measuring the intensity at 72 regularly spaced polarizer/analyzer settings. It is found that the effects of interferometric polarization, beam wandering, and detector dichroism cannot be neglected. However, these error sources have been eliminated by analyzing zeroth, second, and fourth harmonic components of the azimuthally recorded intensity. Both the multiplex advantage of Fourier transform spectroscopy and the phase sensitivity of ellipsometry are combined in this instrument. Measurements on superconducting films, superlattices, and doped GaAs films are reported., An automatic infrared ellipsometer to study surface and interface phenomena is constructed based on a Fourier transform spectrometer equipped with an ellipsometer unit. Polarizer and analyzer rotation is guided by a computer-controlled stepping- motor system. Intensity measurements at 72 regularly spaced polarizer and analizer settings determine the reflected beam's polarization state. Analyzing the zeroth, second and fourth harmonic components of the recorded intensity eliminates error sources such as interferometric polarization, beam wandering and detector dichroism.

It is well known that the crystalline quality of CdxHg1-xTe grown by molecular beam epitaxy is critically dependent on the substrate temperature. The optimal growth temperature has been identified immediately below the crossing of the Te-rich phase boundary, that is just below the temperature range where Te precipitation occurs in the layer. It is potentially very useful to be able to predict the optimal temperature and its variation with other growth parameters, but no general guidelines for this can be found in the literature. We have studied experimentally the variation of the optimal growth temperature with Hg flux, Cd mole fraction and growth rate. These results are compared with a thermodynamical model published previously by Gailliard. We find that the modeled position of the phase boundary coincides well with the observed variations in optimal growth temperature for growth on Te-terminated surfaces, within the uncertainties of available thermodynamical constants. We show that the optimal substrate temperature depends mainly on the Hg flux and Cd mole fraction, while the dependence on growth rate can be neglected in practical molecular beam epitaxy conditions. The experimental observation of optimal layer quality at the phase boundary could suggest the existence of an adsorbed layer of Te, acting as a reservoir for Te atoms and reducing the supersaturation of the growth reaction. Simultaneous growth on the (211)B and (100) orientations reveals a clear, although not very large, difference in optimal growth temperature and Cd incorporation, indicating a difference in growth kinetics. This can be accounted for in the thermodynamical model by condensation and evaporation coefficients. [ABSTRACT FROM AUTHOR]