Abstract

Future needs for high performance optical systems place new demands on rapid fabrication of high quality glass mirror configurations and on the way in which the materials such as fused silica are produced for these large, lightweight, aspheric systems. Conventional fabrication techniques for large mirror blanks involve time-consuming assembly, machining, and grinding operations to achieve the lightweight and surface curvature. An alkali silicate gelation process was developed which is capable of casting near-net-shape mirror core segments which retain their geometry and integrity despite linear shrinkages of ~50% through the densification cycle. Small scale mirrors (with frit attached gel faceplates) were fabricated up to ~15 cm in diameter by a relatively rapid process. The advantage of the aqueous silicate gel approach lies in the ability to control the mean pore diameter to >2000 Å which permits rapid crack-free drying of the monoliths in a microwave oven.

© 1989 Optical Society of America