Aluminum Oxide (Al2O3) Revisited
Publisher Summary This chapter discusses the optical properties of aluminum oxide (AI2O3). The anisotropic optical constants of aluminum oxide from 0 to 116 eV are described. The hexagonal form of aluminum oxide is variously called “alumina,” “corundum,” “ruby,” or “sapphire.” It is a hard, stable material melting at 2319 K. AI2O3 is a negative, uniaxial crystal transparent from 0.145 to 5.0 μm and 0.147 to 5.2 μm. It is noted that optical anisotropy is small from the extreme ultraviolet through the infrared, becoming larger in the microwave region. Optical-quality crystalline aluminum oxide is made by several techniques including: Czochralski growth, flame fusion, the heat-exchanger method (HEM), and the edge-defined, film-fed growth techniques. The high mechanical and dielectric strength of AI2O3 makes it a desirable laser host material. Chromium and titanium-doped aluminum oxide are common solid state laser-gain media. Gervais used a compilation of optical constants for amorphous AI2O3 that do not contain information on the anisotropy of the crystalline state. The information was supplemented with single-crystal and polarization measurements.