INFRARED PROPERTIES OF CHEMICAL-VAPOR-DEPOSITION POLYCRYSTALLINE DIAMOND WINDOWS

Low-resolution transmittance and reflectance spectra of high-quality c hemical-vapor deposition (CVD) diamond windows were measured in the in frared in the 2.5-500-mu m wavelength range (20-4000 cm(-1)). High-res olution measurements on a window with nearly parallel surfaces show we ll defined interference fringes at low frequencies. By standard proced ures the optical constants n and K of CVD diamond were determined, for the first time to the author's knowledge, in the far-infrared region. It is shown that a window with a large wedge angle, close to 1 degree s, does not produce appreciable interference fringes. Modeling of thes e results confirms that interference fringes can be avoided by use of properly wedged CVD diamond windows. This result is of considerable re levance to the use of CVD diamond windows in spectroscopic application s for which fringe suppression is a major requirement. (C) 1998 Optica l Society of America.