Use of Diamond as an Optical Material

Abstract : Chemical vapor deposition (CVD) processes promise inexpensive diamond optics and coatings with large dimensions. Near term optical applications include x-ray windows, membranes for x ray lithography, and infrared windows and domes. CVD diamond, which is mainly polycrystalline, shows materials problems that include scattering due to large surface roughness, absorption due to defects, non diamond carbon phases, and impurities, and poor diamond/substrate adhesion. Free carrier absorption in CVD diamond has also been reported. While diamond films less than 3 um thick can be made transmissive in the visible and in the ultraviolet, at these wavelengths, thicker components scatter excessively and show absorption due to defects. Continuing research is improving the optical quality of CVD diamond. New polishing methods have yielded smooth surfaces in reasonable polishing times. Recent research holds promise for large optics made from single crystal diamond.