Rapid, noncontact, damage free shaping of optical and other surfaces with plasma assisted chemical etching

Experimental results are presented demonstrating that plasma-assisted chemical etching (PACE) can rapidly and controllably figure (shape) and smooth optical surfaces without mechanical contact. This process, for example, significantly reduces the constraints on the design of quartz optical elements imposed by mechanical processes, such as the requirement of substrate rigidity and the limitation of sphericity of the resulting surface. The pertinent chemistry and physics of this process is summarized to provide a basis for understanding its characteristics. A theory of surface evolution applicable to PACE is used to show the range of surface topographies predicted for PACE. It is shown, among other things, that both isotropic and anisotropic etch processes intrinsically microsmooth features smaller than 0.1 mm, and that removal smooths while deposition roughens