| 摘要 |
There is disclosed a method and apparatus for providing optically pure water-free fused silica blanks, tubing and crucibles for use in forming optical waveguides, lenses, prisms, filters, and high temperature lamp envelopes, in which soot is deposited on a high purity graphite bait or refractory low expansion glass, glass-ceramic or suitable crystalline ceramic bait by a flame hydrolysis method in which the burner is located close to the bait. This results in an exceptionally dense soot preform. The preform is later sintered in an inert dry atmosphere by slowly inserting the soot covered bait into a furnace in such a manner that entrapped gas is forced from the fused silica during the slow insertion into the furnace maintained at a temperature above 1,400 DEG C. The formation of bubbles within the fused silica is prevented because of the inert atmosphere and because the gases in the preform escape through the unsintered portions of the preform, thereby providing a crucible or blank of fused silica of exceptionally high optical quality. |
