Infrared transmission properties of sapphire, spinel, and yttria as a function of temperature

The characterization of the bulk absorption and scattering properties of sapphire, spinel, and yttria, as a function of temperature, is accomplished using a Bomem DA3.02 Fourier transform spectrometer and a heated cell. The measurements are performed between 2 μm and 20 μm and from room temperatures to 775 K. The ratio of the spectra of two samples of different thicknesses is taken to eliminate mutual surface effects and to provide a direct measure of the bulk extinction coefficient. The absorption coefficient data are used to determine parameters in a multiphoton absorption model. The model has proven valid up to the melting temperature of the material. Therefore, an accurate means of interpolating and extrapolating the data is obtained. A comprehensive characterization of the material's absorption properties with frequency and temperature is realized