High-power lasers are making increasing demands on laser hosts especially in the area of thermal management. Traditional hosts, such as YAG, are unsuitable for many high-power applications and therefore, new hosts are being developed including rare-earth sesquioxides. We report new measurements of the refractive indices of these materials as functions of wavelength and temperature, which will aid in the design of laser cavities and other nonlinear optical elements.

Infrared absorption of high-quality, commercial, polycrystalline MgAl 2 O 4 spinel is ∼40% greater in the range of 3.8 to 5.0 μm than the value predicted by the computer code OPTIMATR®, which has been used for window and dome design for more than 20 years. As a result, spinel and a-plane sapphire windows designed to support the same external pressure with the same probability of survival have approximately the same infrared absorptance in the range 3.8 to 5.0 μm. c-Plane sapphire has greater absorptance than spinel in the range 3.8 to 5.0 μm. Spinel has two weak absorption bands near 1.8 and 3.0 μm. At 1.064 μm, the laser calorimetric absorption coefficient of spinel is 10 to 50 times greater than that of sapphire. New measurements of specific heat capacity, thermal expansion, thermal conductivity, elastic constants, and refractive index (including dn∕dT ) of spinel are reported. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 05/26/2015 Terms of Use: http://spiedl.org/terms Optical Engineering 087113-2 August 2013/Vol. 52(8) Harris et al.: Optical and thermal properties of spinel with revised (increased) absorption. . . Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 05/26/2015 Terms of Use: http://spiedl.org/terms

The refractive indices and thermo-optic coefficients for varying concentrations of Er3+ doped polycrystalline yttria were measured at a variety of wavelengths and temperatures. A Lorenz oscillator model was employed to model the room temperature indices and thermo-optic coefficients were calculated based on temperature dependent index measurements from 0.45 to 1.064 microns. Some consequences relating to thermal lensing are discussed.

The refractive indices of Yb:YAG crystals for 0, 1, 3, 5, 7, and 10 at. % Yb were measured from 0.4-5.2 microns. The coefficients for the Sellmeier fit are reported. The absorption at room temperature was measured from .185-3.3 microns. Using the index and spectroscopic data, the oscillator strengths for the samples were calculated, and their dependence on dopant concentration examined.