High-performance IR windows for thermal imaging, FLIR systems, and CO₂ laser applications
When specifying this product, these parameters most directly impact performance and cost:
| Material | Germanium (Ge), single-crystal, high-resistivity |
|---|---|
| Transmission Range | 2 – 14 μm (opaque below 2 μm) |
| Refractive Index | ~4.0 @ 10.6 μm |
| Density | 5.32 g/cm³ |
| Hardness | 6 Mohs |
| Diameter Range | 5 – 100 mm (custom up to 150 mm) |
| Thickness Range | 1 – 50 mm |
| Surface Quality | 40-20 standard; 20-10 available |
| Surface Flatness | λ/10 @ 632.8 nm (custom available) |
| Coatings | Dual-band AR (3-5 / 8-14 μm) or single-band AR (10.6 μm) |
Parameter Reference Guide
Typical Standard capability — available as shown
Available Alternative options exist — request quotation
Custom Per your drawing — quote after review
Subject to Review Depends on project specifics
When requesting a quote for optical windows, providing the following information helps us give you an accurate quotation:
Germanium optical windows are flat, parallel substrates cut from single-crystal germanium. They provide excellent transmission in the mid-wave IR (3–5 μm) and long-wave IR (8–14 μm) atmospheric windows, making them the standard material for thermal imaging and infrared optical systems.
With a refractive index of approximately 4.0, Germanium windows require AR coatings to achieve usable transmission. Uncoated Ge surfaces reflect approximately 36% per surface, yielding only ~41% total transmission through both faces.
Reference data — verify with PhotonEdge for project-specific specifications.
| Property | Value | Notes |
|---|---|---|
| Transmission Range | 2 – 14 μm | Opaque below ~2 μm |
| Refractive Index | ~4.0 @ 10.6 μm | High — AR coating essential |
| Density | 5.32 g/cm³ | Heavy compared to ZnSe or Si |
| Hardness | 6 Mohs | Surprisingly durable for IR material |
| CTE | 6.1 × 10⁻⁸ /K | Moderate thermal expansion |
| Thermal Conductivity | 60 W/(m·K) | Good heat dissipation |
| dn/dT | 4.0 × 10⁻⁸ /K | Significant — focus shift at elevated temps |
| Melting Point | 938°C | Not suitable for extreme heat |
Broadband AR for MWIR and LWIR simultaneously. Essential due to high uncoated reflection (~36% per surface).
Ideal for thermal imaging systemsOptimized for CO₂ laser wavelength. R < 0.5% per surface.
Best for CO₂ laser cutting and markingProtective layer for harsh environments. Extends window life in outdoor or industrial applications.
Outdoor FLIR and surveillance systemsAbove 100°C, Ge absorption increases significantly (dn/dT = 4.0×10⁻⁸/K). For high-power CO₂ lasers, verify thermal stability with beam diameter and duty cycle analysis.
High refractive index (~4.0) means ~36% Fresnel reflection per surface. AR coatings are mandatory for any transmission application. Uncoated transmission is only ~41%.
Ge is completely opaque below ~2 μm. It cannot be used for visible alignment or laser sighting. Use a co-aligned visible laser for system alignment.
At 5.32 g/cm³, Ge is significantly heavier than ZnSe (5.27) or Si (2.33). Factor weight into portable or airborne thermal systems.
LWIR camera windows and protective optics for defense, surveillance, and security systems operating in the 8–14 μm band.
Protective and output windows for 10.6 μm CO₂ laser cutting, welding, and marking systems.
IR-transparent windows for Fourier transform infrared spectrometers and gas analysis cells.
Windows for infrared imaging in semiconductor wafer inspection and process monitoring.
Contact us for exact pricing based on your specifications.
Specification Parameters
Typical Specifications shown on this page are standard capabilities. Available Options include alternative materials and coatings. Custom Specifications are available per your drawing. Requirements beyond standard capability are marked Subject to Engineering Review.
Germanium has a very high refractive index (~4.0), causing ~36% Fresnel reflection per surface. This is why AR coatings are essential — without coating, only ~41% of light transmits through both surfaces.
Yes. The dn/dT of 4.0×10⁻⁸/K causes focus shift with temperature changes. Above 100°C, absorption increases significantly. Compensate in system design or limit operating temperature.
Yes. Germanium is compatible with vacuum environments and has relatively low outgassing. It is commonly used in space-borne IR instruments.
Standard diameters range from 5mm to 100mm with thicknesses from 1mm to 50mm. Larger sizes and custom shapes are available upon request.
Ge is harder (6 vs 2.5 Mohs) and less expensive, but ZnSe offers broader transmission (0.5–20 μm) and better thermal stability for high-power applications.
Yes. Circular, rectangular, square, and custom shapes are available. Provide your drawing or dimensional requirements for a quotation.
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