Extreme Hardness
Mohs hardness of 9 provides exceptional resistance to scratching, abrasion, and erosion.
Sapphire Optical Material
Sapphire (Al₂O₃)
Extraordinary Strength. Exceptional Optical Performance.
Single-crystal aluminum oxide engineered for demanding optical systems requiring exceptional hardness, thermal stability, chemical resistance, and broad spectral performance.
Why Sapphire
Engineered for Optical Systems That Cannot Compromise
Sapphire combines optical transmission with outstanding mechanical and environmental durability, making it an excellent choice for exposed windows, sensor covers, laser systems, semiconductor equipment, and high-temperature assemblies.
Broad Transmission
Useful transmission from deep ultraviolet through visible and near-infrared wavelengths.
Thermal Stability
Maintains structural performance at elevated temperatures and during thermal cycling.
Chemical Resistance
Excellent resistance to corrosive chemicals, moisture, and harsh process environments.
Engineering Properties
Mechanical, Thermal, and Optical Performance
Representative values for optical-grade single-crystal sapphire. Final specifications should be confirmed for orientation, wavelength, geometry, and operating environment.
Physical & Mechanical Properties
| Chemical Formula | Al₂O₃ |
|---|---|
| Crystal Structure | Trigonal (rhombohedral) |
| Density | 3.98 g/cm³ |
| Mohs Hardness | 9 |
| Young’s Modulus | Approximately 345 GPa |
| Poisson’s Ratio | Approximately 0.25 |
| Maximum Service Temperature | Application-dependent; up to approximately 2,000°C in suitable environments |
Optical & Thermal Properties
| Transmission Range | Approximately 0.18–5.5 µm, uncoated |
|---|---|
| Refractive Index | Approximately 1.76 at 550 nm |
| Birefringence | Present; depends on crystal orientation |
| Thermal Conductivity | Approximately 35 W/m·K at room temperature |
| CTE | Orientation-dependent; approximately 5–8 × 10⁻⁶/K |
| Coating Compatibility | AR, protective, reflective, and custom spectral coatings |
| Available Orientations | C-plane, A-plane, R-plane, and custom orientations |
Optical Transmission
Broad Spectral Performance
Uncoated sapphire offers useful transmission from the deep UV into the mid-infrared. Actual transmission depends on thickness, orientation, surface finish, and coatings.
Representative only. Final performance varies with crystal quality, orientation, thickness, surface finish, and optical coating.
Material Comparison
Where Sapphire Delivers the Greatest Advantage
| Property | Sapphire | BK7 | Fused Silica | CaF₂ |
|---|---|---|---|---|
| Scratch Resistance | Excellent | Moderate | Good | Low |
| High-Temperature Use | Excellent | Limited | Very Good | Moderate |
| UV Transmission | Very Good | Limited | Excellent | Excellent |
| Chemical Durability | Excellent | Good | Excellent | Moderate |
| Relative Cost | Higher | Low | Moderate | Higher |
Manufacturing Capabilities
From Sapphire Blank to Finished Optical Component
Integrated fabrication supports prototypes, low-volume builds, and repeat production with documented quality control.
Precision Machining
Core drilling, slicing, shaping, edge finishing, and complex geometry control.
Optical Polishing
Precision lapping and polishing for demanding flatness and surface-quality requirements.
Optical Coating
AR, protective, reflective, and application-specific spectral coating options.
Quality Assurance
Dimensional inspection, interferometry, surface inspection, and documentation.
Design Guide
Specify the Right Sapphire Component
Include operating wavelength, crystal orientation, dimensions, tolerances, surface quality, flatness, parallelism, edge treatment, coating, quantity, and environmental requirements.
Discuss Your SpecificationSurface QualityCommercial to precision grades
FlatnessApplication-specific interferometric control
ParallelismPrecision wedge and parallelism options
Edge TreatmentChamfer, bevel, radius, and custom profiles
CoatingsSingle-band, broadband, protective, and custom
DocumentationInspection reports and traceability available
Related Optical Components
Custom Sapphire Components
Precision components can be manufactured to drawing, sample, or application requirements.
Frequently Asked Questions
Sapphire Material FAQs
What wavelength range does sapphire transmit?
Optical-grade sapphire is commonly used from the deep ultraviolet through visible and near-infrared wavelengths, with useful transmission extending into the mid-infrared. Exact performance depends on thickness, crystal quality, orientation, polish, and coatings.
Which crystal orientation should I specify?
C-plane is common for many window applications, while A-plane, R-plane, and other orientations may be selected for birefringence, mechanical, thermal, or process considerations. The best choice depends on your optical system.
Can sapphire receive anti-reflection coatings?
Yes. Sapphire can be coated with single-band, broadband, protective, reflective, and custom spectral coatings designed around the operating wavelength and environment.
Can COE manufacture custom shapes and tolerances?
Yes. Custom diameters, rectangles, wedges, holes, slots, edge profiles, rods, substrates, and other geometries can be evaluated against your drawing and performance requirements.
Need Custom Sapphire Optical Components?
Send your drawing, wavelength, tolerance, coating, quantity, and application requirements to our engineering team.