We discuss an optical interferometer's beamsplitter from the points of view of visibility loss and phase, critical to astrometry. A beamsplitter having no symmetries is described by 16 parameters, all functions of optical frequency; if all symmetries are present this number is reduced to four, only two of which are relevant to astronomical interferometry. We have developed a novel multi-layer design which covers fully a factor of three in wavelength while contributing a minimum of visibility loss, light loss, and systematic error.
Diamond grown with chemical vapor deposition (CVD) processes is currently being considered for use as a long wave infrared (LWIR) dome material for advanced missiles. In order to assess diamond's suitability for this application, a complete understanding of the optical properties of CVD diamond is needed. This includes a determination of the relative amount of bulk and surface scattering, and a measurement of the absorption in thick CVD diamond films. In this paper, we present scattering data for visible (0.633 micrometers ) and infrared (10.6 micrometers ) wavelengths from optically smooth thick diamond films. Scattering data from the aluminized front and back surfaces of the films is also reported. These measurements, together with first order scattering theory, provide a means for determining the component of scattered radiation which is due to bulk scattering. The bulk absorption is also estimated from a detailed energy balance using reflectance, transmittance and scattering measurements.
A thermochemical polishing technique (using low carbon steel at 700 degree(s)C to 900 degree(s)C) was employed to reduce the roughness on the surface of diamond films from 20,000-40,000 angstroms rms to 30-45 angstroms rms. These polycrystalline films were grown by filament assisted chemical vapor deposition (FACVD) onto (100) oriented silicon substrates. SEM micrographs reveal etch pits in the films, and these limit the final polish which can be achieved. This paper show that the hot iron technique polishes a (111) oriented film, which is the hardest direction for abrasive polishing. Preliminary studies indicate that for chemical polishing there is no large difference between the polishing rates of diamond as a function of orientation.
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