LWIR SPECTRAL PROPERTIES OF CVD DIAMOND AT CRYOGENIC TEMPERATURES

The infrared emittance and transmittance spectra of a chemical vapor-d eposited diamond substrate were determined at 4.2, 77 and 295 K. The m ultiphonon region was analyzed under varying degrees of spectral resol ution. No variance in spectral properties over this temperature range was observed beyond measurement uncertainty. The refractive index of t he material was determined in the 3-21 micron spectral region at cryog enic temperatures. The absorption coefficient was also determined and shown to vary from 11.7 cm(-1) in the short wave 2 phonon region to 0. 79 cm(-1) at longer wavelengths. The results indicate that chemical va por-deposited diamond possesses significant potential for use as windo ws, filter substrates and optical component coatings in long-wave infr ared systems.