Broad Spectral Transmission
Useful transmission from the ultraviolet through the visible and into the near infrared, grade and thickness dependent.
Fused Silica
Fused Silica Optical Material
High-Purity Performance from Ultraviolet to Near-Infrared.
A high-purity amorphous silica material offering broad spectral transmission, very low thermal expansion, excellent thermal-shock resistance, and strong environmental stability for precision optical systems.
Why Fused Silica
A Premium Material for UV, Laser, and Thermally Demanding Optics
Fused silica combines high optical purity with low thermal expansion and excellent resistance to thermal shock. It is widely selected for ultraviolet systems, precision laser optics, semiconductor equipment, metrology, high-temperature windows, and scientific instrumentation.
Very Low Thermal Expansion
Excellent dimensional stability under temperature changes supports demanding optical alignment and wavefront control.
High Thermal-Shock Resistance
Low expansion and strong thermal stability help the material tolerate rapid temperature cycling.
High Optical Purity
Low absorption and strong homogeneity make fused silica suitable for precision imaging and laser applications.
Engineering Properties
Optical, Mechanical, and Thermal Characteristics
Representative values for optical-grade fused silica. Final values vary by grade, manufacturing route, wavelength, hydroxyl content, thickness, and test method.
Physical & Mechanical Properties
| Material Type | Amorphous silicon dioxide (SiO₂) |
|---|---|
| Density | Approximately 2.20 g/cm³ |
| Knoop Hardness | Approximately 500–600 |
| Young’s Modulus | Approximately 72–74 GPa |
| Poisson’s Ratio | Approximately 0.16–0.17 |
| Thermal Expansion | Approximately 0.5–0.6 × 10⁻⁶/K |
| Maximum Service Temperature | Application and grade dependent; suitable for elevated-temperature use |
Optical Properties
| Transmission Range | Approximately 0.18–2.5 µm, grade and thickness dependent |
|---|---|
| Refractive Index nd | Approximately 1.4585 |
| Abbe Number Vd | Approximately 67.8 |
| Dispersion | Low dispersion with stable optical performance |
| Birefringence | Isotropic; stress birefringence depends on processing and mounting |
| Coating Compatibility | UV, VIS, NIR AR, reflective, beamsplitter, and custom coatings |
| Available Grades | UV-grade, IR-grade, low-OH, high-OH, and high-homogeneity grades |
Optical Transmission
Strong UV-to-NIR Transmission
Fused silica is valued for broad transmission and low absorption. Actual performance depends on material grade, hydroxyl content, thickness, surface finish, and coating design.
Representative only. Final transmission depends on grade, OH content, thickness, surface finish, and coating.
Material Comparison
When Fused Silica Is the Best Fit
| Property | Sapphire | BK7 | Fused Silica | CaF₂ |
|---|---|---|---|---|
| UV Performance | Very Good | Limited | Excellent | Excellent |
| Visible Imaging | Very Good | Excellent | Excellent | Very Good |
| Thermal Expansion | Low | Moderate | Very Low | Moderate |
| Scratch Resistance | Excellent | Moderate | Good | Low |
| Relative Cost | Higher | Low | Moderate | Higher |
Manufacturing Capabilities
From Fused Silica Blank to Finished Optical Component
COE Sapphire supports prototype, low-volume, and repeat production of precision fused silica components with integrated fabrication, coating, and inspection.
Precision Machining
Cutting, coring, edging, beveling, drilling, and custom geometry fabrication.
Optical Polishing
Precision flat, spherical, and custom polishing for demanding wavefront and surface requirements.
Optical Coating
UV, visible, NIR AR, reflective, beamsplitter, and application-specific multilayer coatings.
Quality Assurance
Dimensional inspection, interferometry, surface inspection, and documentation.
Design Guide
Specify the Right Fused Silica Optical Component
Provide grade, operating wavelength, dimensions, tolerances, surface quality, flatness, wedge or parallelism, clear aperture, edge treatment, coating, quantity, and environmental requirements.
Discuss Your SpecificationMaterial GradeUV-grade, IR-grade, low-OH, high-OH, or specified equivalent
Surface QualityCommercial through precision optical grades
FlatnessApplication-specific interferometric control
Wedge / ParallelismPrecision parallel, wedged, or custom geometry
Edge TreatmentChamfer, bevel, radius, polished or ground edges
CoatingsUV, VIS, NIR, reflective, and custom multilayer coatings
Related Optical Components
Fused Silica Components Manufactured to Your Specification
Frequently Asked Questions
Fused Silica FAQ
What is fused silica commonly used for?
Fused silica is widely used for UV windows, laser optics, semiconductor systems, metrology, high-temperature windows, imaging components, and scientific instruments.
What wavelength range can fused silica transmit?
Optical-grade fused silica can provide useful transmission from the deep ultraviolet through the visible and into the near infrared, depending on grade and thickness.
How does fused silica compare with BK7?
Fused silica offers better UV transmission, much lower thermal expansion, and better thermal-shock resistance. BK7 is usually more economical for general visible optics.
How does fused silica compare with sapphire?
Fused silica provides lower thermal expansion and stronger deep-UV performance, while sapphire offers far greater hardness and abrasion resistance.
Can fused silica be optically coated?
Yes. It is compatible with UV, visible, near-infrared AR, reflective, beamsplitter, and custom multilayer coatings.
Can COE Sapphire manufacture custom fused silica shapes and tolerances?
Yes. COE Sapphire can manufacture custom dimensions, wedges, bevels, radii, apertures, holes, polished surfaces, and application-specific tolerances.
What information is needed for a fused silica quotation?
Please provide material grade, dimensions, tolerances, surface quality, flatness, wedge or parallelism, clear aperture, coating, quantity, and required inspection documentation.
Custom Fused Silica Optical Components
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