Surface figuring of silicon carbide using chemical etching methodologies

Coming OCA has completed a set of feasibility studies into improved technologies for the figuring and finishing of precision aspheric optical surfaces on silicon carbide (SiC) employing two innovative chemical etching processes: plasma-assisted chemical etching (PACE) and photoelectrochemical etching (PECE). Researchers completed preliminary investigations into the material removal methodologies and the physical characteristics of the resulting surfaces. All three classes of commercially available optical grade SiC were tested: hot-pressed (alpha-SiC), chemical vapor deposited (CVD) (beta-SiC) and reaction bonded (RB-SiC). Coming OCA demonstrated that controlled, localized surface removal was achievable for both PACE and PECE methodologies. These studies have resulted in a better understanding of how to generate and finish low subsurface damage optical surfaces on lightweight SiC mirrors and thus achieve cost effective ultra-lightweight mirrors of unparalleled stability. Coming OCA believes that these results demonstrate the fundamental feasibility of these technologies for application in the optical manufacturing of high performance SiC mirrors.