Chemical Vapor Composite (CVC) Silicon Carbide (SiC) material has demonstrated superior optical polishing properties
and high specific stiffness characteristics. These unique characteristics make CVC SiC a highly desirable material for
aerospace reflective optics applications. The lack of material fabrication processes for CVC SiC has hindered the
introduction of this material into the aerospace marketplace. Traditional methods of fabrication such as diamond
grinding and lapping have proven to be expensive for CVC SiC material in aperture diameters that approximate 25cm or
larger. Because of the extreme hardness of CVC SiC, the material removal rates are low and therefore larger size parts
become very time consuming and thus cost prohibitive. Over the past two years several development efforts have been
focused specifically toward fabrication technologies and methods to enhance the economical producibility of CVC SiC
material. The results of these development efforts have revealed viable economical fabrication processes for CVC SiC.
These fabrication processes have demonstrated material removal rates that are vastly greater than that of traditional
diamond grinding and lapping process. This paper describes fabrications technologies and processes and material
removal rates for fabricating monolithic, ultra pure, optical grade CVC SiC material.
Components for space telescopes using high quality silicon carbide (SiC) produced via the chemical vapor composite (CVC) process are currently under development. This CVC process is a modification of chemical vapor deposition (CVD) and results in a dramatic reduction in residual stress of the SiC deposit. The resultant CVC SiC material has high modulus, high thermal conductivity and can be polished to better than 1nm RMS surface roughness, making it ideal for space telescopes requiring lightweight, stiff and thermally stable components. Moreover, due to its lower intrinsic stress, CVC SiC is much more readily scaled to large sizes and manufactured into the complex geometries needed for the telescope assemblies. Results are presented on the optical figure for a lightweight 15cm CVC SiC mirror demonstrating low wavefront error (<30nm peak-to-valley and <5.1nm rms). Theoretical and experimental modal analysis measured the first four resonant modes of the mirror and found a first modal frequency in the vicinity of 2100 Hz, representing a highly stiff mirror.
We report the performance of a very high repetition rate ArF laser optimized for next generation, high NA, high throughput scanner. The laser's repetition rate exceeds 4kHz, at 5mJ, and at bandwidths of less than 1.2 pm. We discuss the complexity of high power operation, and make some estimates about the robustness of this technology. In particular, we discuss the risks of scaling to this high repetition rate, and prospects of exceeding 4kHz to near 6kHz with 95 percent bandwidths of less than 1pm.