Form 9.B Project Summary



Proposal Number:


Project Title:

Fabrication and Polishing of Uncoated

Silicon Carbide Aspheric Optical


Technical Abstract (Limit 200 words)

Silicon Carbide (SiC) optics are a key technology

for future NASA missions including Next

Generation Space Telescope (NGST). SiC has

superior thermal stability and excellent specific

stiffness making it ideal for space based system

applications. Flat and spherical optical surfaces can

be obtained directly on SiC materials using

conventional polishing systems. The problem has

been in obtaining non-symmetric aspheric surface

profiles (i.e.;hyperbolic, elliptical or parabolic

contours). A common solution is to coat SiC optics

with a thin layer of silicon prior to optical finishing.

Silicon can be easily polished and the slight

coefficient of thermal expansion (CTE) mismatch

between SiC and silicon is not an issue for most

applications. SSG proposes to develop an

innovative fabrication process which will facilitate

polishing of uncoated SiC aspheric optical surfaces.

The proposed approach will modify and improve the

casting, machining and polishing steps in SiC

fabrication. Several innovative techniques will be

used including diamond micromachining, automated

lap polishing, high speed spot polishing, flow

polishing and ion figuring. SSG has already done

some preliminary work in these areas, producing a

0.75 wave pk-valley off-axis parabola in a 4.5"

diameter SiC sample. The effort proposed will

provide SiC optics which are superior to the current

state-of- the-art silicon coated SiC optics in several

ways: improved thermal stability, improved

reflectivity in the EUV spectral region, reduced

manufacturing cost/time, and eliminating residual

stresses created by the silicon coating process. In

Phase I SSG will develop and refine the innovative

manufacturing process proposed. The viability of

the techniques proposed, and the improvements

obtained with the uncoated SiC substrates, will be

demonstrated by fabrication and testing of a

proof-of-concept off-axis parabolic reflector.

Potential Commercial Applications (Limit 200 words)

The availability of cost effective, bare SiC aspheric

optical surfaces will open up a number of important

commercial applications. Reductions in cost, and

improvements in EUV reflectivity and thermal

stability make the technologies proposed here very

interesting for EUV lithographic projection optical

systems. SSG has already begun discussions with

Silicon Valley Group (SVG) Lithography with

regard to transitioning the optical

fabrication/polishing processes referenced here.

Name and Address of Principal Investigator (Name,

Organization Name, Mail Address, City/State/Zip)

Joseph Robichaud

SSG, Inc.

65 Jonspin Road

Wilmington , MA 01887

Name and Address of Offeror (Firm Name, Mail Address,


Alan H. McEacharn

SSG, Inc.

65 Jonspin Road

Wilmington , MA 01887