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   Technology Profile#680    1/10/2006
Silicon Carbide Optics

Summary:

SSG has developed a silicon-carbide (SiC) fabrication process to make lightweight satellite mirrors that are less toxic and more thermally stable than beryllium, a commonly used material in space applications. MDA predecessor BMDO funded the company's technology through several projects, including projects geared toward telescopes for the ground-based interceptor program, now MDA’s exoatmospheric kill vehicle program. The new technology also is being developed for use in the semiconductor lithography industry, for applications including wire bonders and lithography stages.



Technology Description:

SSG's technology includes techniques for producing optical substrates and mirror cladding that can be used in a wide range of spaceborne and tactical applications.

Key among the benefits of SiC optics is the material's nontoxicity. Beryllium, a naturally occurring metal, can damage the lungs of people working with it. SiC, meanwhile, is about as toxic as sand—which is to say harmless. And SiC is easily acquired, while beryllium must be mined and carefully machined. SSG uses a simple casting approach instead of intensive machining to produce SiC lightweight mirrors.

The SiC approach also boasts time savings. In a production scenario, the SiC castable process will support substrate fabrication in a matter of weeks, compared with six months or more with competing materials such as beryllium or glass, according to the company. Moreover, SiC in optics has thermal stability that is six to seven times better than beryllium, which is even more thermally stable than aluminum. SiC optics will operate at or below 50 Kelvin and can withstand heat generated by visible sunlight. And SiC optical telescopes have demonstrated visible optical quality performance, which is important in lidar applications.

SSG's technology includes both SiC substrates and cladding techniques and telescope metering structures. Conventionally, manufacturers make precision lightweight mirrors by coating nickel on beryllium optics. In SSG's process, however, the company takes the SiC substrate (analogous to a piece of pottery or a dish that is very lightweight) and applies a silicon cladding. The company then follows its standard finishing steps, including diamond turning and computer-controlled optical surfacing at its Tinsley Laboratory Division.



MDA Origins:

With Phase I and Phase II SBIR awards, MDA predecessor BMDO originally funded the company's technology for demonstration in telescopes for the ground-based interceptor program, now MDA’s exoatmospheric kill vehicle program.

BMDO actually funded several SSG SiC optics projects, advancing know-how at the company and contributing to material development efforts. Funded projects have included SBIR Phase II awards for SiC steering mirrors for high-energy laser applications and an SiC optical telescope for next-generation midcourse interceptors, as well as SBIR Phase I awards for reaction-bonded SiC for MDA seeker telescope applications; high-performance optical coatings for SiC advanced seeker systems; innovative aspheric surface generation of SiC optics; an SiC all-reflective telescope supporting spiral upgrades for emerging kill-vehicle architectures to counter future ballistic missile threats; rapid-stressed mirror polishing of SiC aspheric mirrors; a lightweight, segmented, deployable SiC optical system; and an SiC optical telescope for next-generation midcourse interceptors.



Spinoff Applications:

SSG’s technology has the potential for use in the semiconductor lithography industry. Wire bonders for computer chips, for example, are one potential application. The company also has explored building structure for lithography stages, which are used to move microchips during fabrication. (Such structure, for example, includes components used to hold together ultra-precise mirrors at exact alignments.) Moreover, SSG is examining SiC mirrors with ultra-low scatter performance for extreme ultraviolet (EUV) laser source assemblies.

In general, SiC can be used for many applications in which beryllium or glass-based materials might traditionally be used. Therefore, most items that use beryllium and require a high degree of “lightweighting” and precision optical performance represent potential applications, according to company researchers.




Commercialization:

The company has successfully flown SiC-based telescopes on two space experimental programs, and it is currently developing SiC telescopes for additional space programs and for a GlobalHawk Reconnaissance camera.

SSG officials' goal is to manufacture both government-related telescope systems and commercial products. Challenges for the company's technology include scaling it up for larger products, improving precision for lithography application, and making the technology less expensive and more production-oriented at both the component level and the subassembly level. SSG continues to seek funds to help commercialize the work it has done in lithography.



Company Profile:

SSG was founded in 1977 by a small group of engineers and scientists with a vision of creating affordable infrared (IR) telescopes for the Department of Defense and government research agencies. SSG’s early contracts provided telescopes to the Air Force Geophysics Laboratory to study IR space backgrounds from space platforms. Over the years, the business expanded from IR telescopes to visible and ultraviolet instruments. In 1986, SSG expanded to the space mechanism business by providing a telescope and scanner for a DOD flight experiment. The scanner and electronics business has grown and many of SSG’s current programs include high-precision mechanisms and flight electronics.

In October 1997, SSG moved its system engineering, design and integration, and test facilities to Wilmington, MA. SSG has grown to more than 200 employees and full-time contractors. The company provides system engineering, design, fabrication, testing, and optics manufacturing to NASA, DOD, major aerospace firms, and several commercial customers.

In December 2001, with assistance from its equity partner, Parthenon Capital, SSG purchased Tinsley Laboratories from ASML, a maker of semiconductor lithography systems. Today, SSG has four facilities: three in Massachusetts and one in California. Its corporate offices and engineering facility, located in Wilmington, MA, support design, fabrication, optical alignment/testing, and optical fabrication within a 65,000-square-foot building. Tinsley Laboratories, located in Richmond, CA, is a 50,000-square-foot facility that houses a modern optical-fabrication capability. And SSG’s Ceramics Division and Optics Division are both located in Massachusetts.



Contact Information:

Mr. Joseph Robichaud
Sensors Systems Group, Inc.
65 Jonspin Road
Wilmington, MA 01887
(978) 694-9991
fax: (978) 694-9922
email: joseph.robichaud@l-3com.com






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