RESUMO
Total internal reflection microscopy has been applied to image subsurface damage sites in conventionally polished fused-silica flats. This technique can differentiate between surface and subsurface features by changing the illuminating polarization. The method is nondestructive, and no surface preparation is required other than a thorough cleaning of the surface. The intensity distributions in the illuminated region of interest are discussed. The technique has been used successfully as an optical fabrication in-process diagnostic.
RESUMO
We present experimental evidence of the dependence of coating scatter on a substrate preparation technique for fused silica substrates. Samples included conventionally polished, superpolished, andfloat-polished substrates. We used scatterometry and total internal reflection microscopy to investigate the effects of substrate preparation on the performance of zirconium oxide thin films. Results indicate that scatter from coatings dominates the scatter signature of the coated optic. They also demonstrate that substrate preparation can affect the level of scatter produced in optical coatings. In addition it is observed that the substrates with the lowest scatter do not necessarily result in the coatings with the lowest scatter.
RESUMO
Ion-beam-figuring techniques have been applied to fabricate high-power transmission gratings for use in photoacoustic spectroscopy. A thin-film assembly of SiO(2) and TiO(2) layers on an SiO(2) substrate provides a high-reflecting characteristic at a desired wavelength. With standard photolithographic techniques a grating pattern is developed on the surface of the assembly then ion etched with ion-beam-figuring techniques. These gratings exhibit an increased factor of 25 in acoustic signal levels when compared with previously used chemical-etched silicon gratings. This increase was obtained owing to higher transmission, less thermal distortion, and the ability to withstand higher incident power levels.
