Optical coefficients of single-crystal and amorphous germanium at elevated temperatures and at 6328 Å

The refractive index and extinction coefficient of single-crystal and for the first reported time amorphous germanium have been measured at the He–Ne wavelength in the temperature range 25–400° C by using the pseudo-Brewster method. The vacuum reflectometer is described, and the correction method for the surface oxide layer is outlined. The results are shown to be consistent with the expected shift of room-temperature spectra with increasing temperature. On this basis it was concluded that the gross features of the high-temperature spectra may be obtained from the room-temperature spectra together with high-temperature measurements at only a few preselected energies.