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

Abstract

Experimental characterization of the bulk absorption properties of sapphire, spinel, yttria, and ALON as a function of temperature is accomplished using a Bomem DA3.02 vacuum Fourier transform spectrometer and a heated cell. The measurements are performed between 2 and 20 microm from room temperatures to 775 K. Spectra of two samples of different thicknesses are ratioed to reduce surface effects and to provide a direct measure of the bulk extinction coefficient. Absorption coefficient and reflectivity data are used to determine parameters in a multiphoton absorption model. The model has proved valid up to the melting temperature of the material. This model provides an accurate means of interpolating and extrapolating the measurements to give a comprehensive characterization of intrinsic absorption properties with frequency and temperature (in the multiphonon region).

Optical constants of refractory oxides at high temperatures

“…Therefore, while fitting our data, we allowed ∞ to vary and could indeed verify a certain temperature dependence for all measured materials, with the general trend toward an increase in ∞ with increasing temperature. This result is supported by the data of Thomas et al (1998a), who compared measured near IR refractive indexes of corundum with their multiphonon model. They found a linear increase of n with increasing temperature, corresponding to a quadratic increase of ∞ (since the absorption is too small to count for in that wavelength range).…”

“…Like the corundum disk the spinel sample has polished surfaces. High-temperature data have already been obtained by Thomas et al (1998a) and by Sova et al (1998). Thomas et al published absorption coefficients in the range of 2.5−10 μm for various temperatures up to 2000 K and a comparison of the results with the multiphonon model.…”

“…They show that the FPSQ model is a more effective way to fit the reflectivity of polar crystals in the case of wide reflection bands where equal damping of the longitudinal optical (LO) and transverse optical (TO) mode cannot be expected any more. On the other hand, Thomas et al (1998a) developed a model that does not need a four-parameter description of the dielectric function but is based on adding temperature-dependent multiphonon contributions to a classical oscillator model. Thomas et al list the parameters for the oscillators, together with their temperature dependence, corresponding to a second-order polynomial fit.…”

Estimation of Optical Properties under High Temperature Conditions

“…절연재료의 파동수 100부터 1000사이의 적외선 영역 에서의 흡수(absorption at the infrared edge)는 멀티포 논 흡수 기구가 관여함이 밝혀졌으며 이온 절연체 (ionic insulator)의 경우 흡광계수 식 (2)로 표현된다 [4] . Table 2.…”

Temperature and Thickness Dependence of IR Optical Properties of Sapphire at Moderate Temperature

“…The optical properties of sapphire have been studied by many researchers; Gryvnak and Burch [1] measured its absorption coefficients from 1 µm to 6 µm up to 2020 • C. Cook and Perkowitz [2] reported the dependence of absorption coefficients in the far-infrared region (∼200 µm) at low temperatures (−213 • C to 27 • C). Thomas and coworkers [3] obtained the absorption coefficients of sapphire from transmittance measurements using a heating laser. A direct emittance measurement of the sapphire had been carried out at elevated temperatures using a heating laser by Sova and coworkers [4].…”