Abstract

A fabrication technique has been developed at the University of Arizona which incorporates the well understood method of fabricating rigid optical components and a method of supporting thin glass substrates so that their flexible nature is transparent to the optician^2,3. Fixing the shell to a rigid monolithic blocking body eliminates the problems of handling and the deflection of the substrate under the forces of polishing. This approach has been demonstrated by the fabrication of shells 1/2 meter in diameter and 2 mm thick. The U of A is currently manufacturing a shell which is 2 meters in diameter and 2mm thick as a demonstration for the NGST⁴.For space applications, the coefficient of expansion of the material at cryogenic temperatures is of concern. For this reason, a borosilicate material (Schott Borofloat) has been selected as the mirror substrate because it has a CTE of zero at 35°K. In this particular case, the selection of material generated the need for adaptation of the earlier process.

© 1998 Optical Society of America