Fused silica is what you specify when the application has already ruled everything else out. Semiconductor lithography equipment, deep UV laser optics, high-precision metrology windows, fluorescence imaging systems, excimer laser cavities — these aren't applications where you compare materials and pick the best value. Fused silica is the answer before the question is finished.

The transmission range tells most of the story: 185nm through 3500nm, clean through deep UV, visible, and into the near-infrared. No standard glass touches that. Borosilicate cuts off around 300nm. If your light source is a UV laser, a deuterium lamp, or an excimer at 193nm, fused silica is the only flat glass substrate that won't absorb the wavelengths you're working with.

Thermal stability is the other reason it appears in precision instruments. The expansion coefficient is one-tenth that of borosilicate. In a laser cavity or an interferometric measurement system, that's the difference between a component that holds alignment through a thermal cycle and one that drifts. For semiconductor fab windows and chemical process enclosures, the near-total chemical inertness matters just as much — fused silica doesn't contribute contamination, doesn't react with process gases, and doesn't degrade in the environments that would compromise anything less pure.

Fabrication requires diamond tooling throughout. Score, drill, and grind with diamond — the material is harder and more brittle than standard glass, and it won't forgive shortcuts. Waterjet works well for flat sheet cutting. Edges polish to an excellent optical finish given the amorphous, isotropic structure.

Available in UV-grade and IR-grade. Custom dimensions to order — contact us with your thickness, format, and application.