Silicon Carbide Optical Surfacing Using Plasma Assisted Chemical Etching

OCA proposes a research program into an improved, automated technology for the finishing of precision silicon carbide (SiC) optical elements employing the plasma assisted chemical etching (PACE) process. Automated fabrication using the PACE process offers significant cost and performance benefits for the generation and finishing of low scatter, low subsurface damage optical surfaces on lightweight SiC mirror substrates. The program will employ OCA's newly constructed PACE aspheric figuring system. Using this system and the new process, we will be capable of producing surfaces figured to precise tolerances with no physical surface contact and completely under computer numerical control. As part of this Phase I program, we will investigate the influence of fundamental operating parameters of the plasma assisted chemical etching process on the resulting surface characteristics of SiC; evaluate pre-PACE surface preparation techniques; define candidate process parameter regimes for use in an automated PACE process; demonstrate process stability and resulting surface characteristics on SiC substrates. Achieving these goals will prove the feasibility of the PACE process and will set the stage for development of a useful manufacturing process for SiC and other important substrate materials in Phase II. OCA envisions several optical applications where the processes resulting from the proposed research can yield significant cost and performance advantages. These areas include silicon carbide mirrors, ultra-low scatter components, zero sub-surface damage optics, inexpensive silicon aspheres, diamond films and complex oxide thinning and figuring.