Effect of polishing technique on the roughness and residual surface film on fused quartz optical flats.

In many optical applications it is desirable to have extremely smooth surfaces to minimize diffusely scattered light and surface plasmon effects. This is particularly important for measurements made in the uv and vacuum uv. In a previous paper one of us has shown that optical surfaces produced by the conventional fresh-feed polishing technique are rougher than those produced by the bowl-feed technique. On the other hand, for measurements made using polarized light, in particular for ellipsometric measurements, the homogeneity of the surface of an optical flat is extremely important. A residual modified layer at the surface left from the polishing process, or a thin dirt layer remaining after cleaning, can drastically affect the apparent thickness and optical