Low temperature bonding of light-weighted mirrors

SCHOTT has developed a Low Temperature Bonding (LTB) technology for fabricating light weight Zerodur((R)) optics without the application of high temperature or pressure. The formation of mechanically stable, optically clear joints between two or more glass or glass ceramic parts can be achieved by simply sandwiching an inorganic, aqueous-based solution between chemically prepared surfaces followed by room temperature or slightly elevated temperature curing regimen. This new technology offers a host of advantages over current technologies including room temperature processing, lower production costs and reduced delivery times as well as broad design flexibility. The LTB technology was used in this study to fabricate a 285mm light-weight plano-plano closed back mirror in an attempt to qualify the bonded assemblies made by this technology for space application. The mirrors were assembled by bonding Zerodur((R)) faceplates onto a Zerodur((R)) core structure, fabricated via abrasive water jet cutting, to produce a light weighted optic with an aerial density of 24.5 kg/m(2). in addition, smaller unit cell structures were also fabricated in a similar fashion for prototype testing. Both the large mirror and the smaller unit cell structures will be measured for surface figure stability before and after thermal cycling and for bonded mechanical strength.