Cryostable Lightweight Frit Bonded Silicon Mirror

Published in SPIE Proceedings Vol. 4822:
Cryogenic Optical Systems and Instruments IX

Frank M. Anthony, Douglas R. McCarter, Matthew Tangedahl, David A. Content

McCarter Technology, Inc. 1312 Underwood Rd. Deer Park, TX 77536NASA Goddard Space Flight Center Optics Branch, MC551  Greenbelt, Maryland


            The excellent polishability, low density and relatively high stiffness of silicon make it an attractive candidate for optical applications that require superior performance.  Assembly of silicon details by means of glass frit bonding permits significant weight reduction thus enhancing the benefit of silicon mirrors.  To demonstrate the performance potential, a small lightweight glass frit bonded silicon mirror was fabricated and tested for cryostability.  The test mirror was 12.5cm in diameter with a 60cm spherical radius and a maximum thickness, at the perimeter, of 2.5cm.  A machined silicon core was used to stiffen the two face sheets of the silicon sandwich.  These three elements were assembled, by glass frit bonding, to form the substrate that was polished.  The experimental evaluation, in a liquid nitrogen cryostat, demonstrated cryostability performance significantly better than required by the mirror specification.

(Our paper can be downloaded here or email Doug McCarter at