• Synthetic Fused Silica

• Standard Zero Length

• 40-20 Scratch-Dig

• Non-Coated Optics

• Six Sizes Available.

ISI’s Fused Silica Viewports are designed and rated for high and ultra-high vacuum applications. They are constructed using vacuum grade materials including high purity silicon dioxide, 304 stainless steel and vacuum tube-grade braze alloys. Fused silica is a polycrystalline, isotropic material with no crystal orientation. Its physical, thermal, dielectric and optical properties are uniform in all directions of measurement. Conventional fused quartz is suitable for basic non-demanding optical applications. Impurities in fused quartz cause a blue-violet fluorescence when exposed to ultraviolet radiation at 253.7µm. This fluorescence is not evident in synthetic fused silica, which is manufactured by flame hydrolysis of silicon tetrachloride.

Infrared fused silica windows with low "OH" content can be quoted for applications requiring IR transmission to about 3600nm. This material has less than 1ppm OH content which eliminates the typical absorption band found in other materials. Fused Silica Viewports are preferred over Glass Viewports because of their transparency to ultraviolet radiation. Other advantages include a higher abrasion resistance and a low coefficient of thermal expansion, making them very resistant to thermal shock. Poor surface finish can contribute as much as 10% to overall  transmission losses. All viewports are supplied with flat faces which have been finished to standards suitable for most applications. ISI’s standard finish for fused silica viewports is 40-20 scratch-dig. Other finishes are available on request at additional cost. For Deep-UV grade materials, the optics industry typically recommends a 20-10 scratch-dig optical finish for service below .25 microns.