Zinc Selenide (ZnSe)
— Laser-Grade Mid-IR Optics, Windows & Blanks
Zinc selenide (ZnSe) is the industry standard material for high-power mid-infrared optics and CO₂ laser systems. Supwafer supplies laser-grade CVD ZnSe and optical blanks, finished windows and lenses with AR/HDT coatings and full metrology (transmission, LDT, surface quality). Request samples or a datasheet to validate for your application.
- Typical transmission: ~0.6 µm – 20 µm (optimized usage: 2–12 µm; excellent at 10.6 µm CO₂ line)
- Refractive index (10.6 µm): ≈ 2.40 (typical)，Density: ~5.27 g/cm³
- Common products: CO₂ laser windows, focusing lenses, IR windows, blanks for machining, prisms, beamsplitters
- Thermal conductivity: moderate (~10–20 W/(m·K), depends on grade)
- Hardness: relatively soft (requires careful handling)
Why ZnSe — engineering rationale
Broad mid-IR transparency: Covers visible alignment light to longwave IR, enabling combined visible/IR alignment and laser operation in the same optic.
Low bulk absorption at 10.6 µm (laser-grade CVD): Minimizes heat generation inside the substrate, reducing thermal lensing and risk of catastrophic damage under high CW power.
Machinability & coating compatibility: Can be diamond-machined, polished to optical quality and coated with AR/HDT stacks for laser use.
Suitability for high-power optics: With appropriate LDT-rated coatings and thermal mounting, ZnSe is the standard for CO₂ laser windows and lenses.
Typical optical & physical specifications
| Property | Typical value / range | Notes |
|---|---|---|
| Transmission range | 0.6 – 20 µm | Effective application: 2–12 µm; verify with transmission curve |
| Refractive index (10.6 µm) | ~2.40 | Use for optical design and AR coating design |
| Absorption coefficient (10.6 µm) | < 0.01 – 0.001 cm⁻¹ (laser-grade) | Low absorption reduces internal heating — request supplier LIDT/LDT data |
| Thermal conductivity | ~10 – 20 W/(m·K) | Moderate — heat sinking recommended for high CW power |
| Density | ~5.27 g/cm³ | / |
| Hardness (Knoop) | 100–150 kg/mm² | Softer than sapphire/SiC — risk of scratches and edge chipping |
| Surface roughness (polished) | Ra ≤ 5 nm (typical) | Depends on polish grade |
| Surface figure / flatness | λ/4 @ design wavelength or µm spec | For windows/lenses specify per application |
| Typical sizes | blanks up to 200 mm dia (custom) | Standard finished sizes depend on stock and machining capability |
Manufacturing & grades
CVD ZnSe (preferred for laser optics): Chemical vapor deposition yields high-purity, low-absorption material commonly used for high-power CO₂ optics. CVD ZnSe exhibits good homogeneity and controlled inclusion levels.
Bulk/melt-grown ZnSe: Available for lower-cost or non-laser critical applications; quality varies with process and may have higher inclusion/absorption.
Grade selection guide:
Laser-grade CVD ZnSe — choose for CO₂ lasers and high LDT requirements.
Optical/IR grade — choose for imaging, spectroscopy, where ultra high LDT is not required.
Research blanks — uncoated blanks for custom machining/testing.
Coatings & laser damage considerations
AR coatings: Single/multi-layer AR coatings tuned to 3–5 µm, 8–12 µm or centered at 10.6 µm.
HDT / high-LDT coatings: Required for CW high-power lasers to avoid coating absorption failure. Validate with supplier LDT (laser damage threshold) test reports (pulse and CW conditions).
Coating adhesion & durability: Request adhesion and environmental testing for process environments (humidity, cleaning, abrasion).
Mounting, thermal management and mechanical design tips
Mounting: Use compliant mounts that avoid point loads on edges; allow for differential thermal expansion. Use O-ring or kinematic mounts where possible.
Cooling: For high CW power windows use water-cooled or conductive mounting to remove absorbed heat.
Thermal gradients: Avoid rapid temperature changes; thermal shock can cause cracking. Preheat/cool designs for high power operation.
Stress relief: Provide compliant interfaces (e.g., indium foil, copper backing) if thermal conduction is needed.
Edge chamfering & polish: Chamfered edges reduce chipping risk; recommend specifying edge finish.
Handling, cleaning & safety
Handle with powder-free gloves, hold by edges only.
Cleaning: Use filtered nitrogen blow, then IPA on lint-free wipes. Avoid abrasives and aggressive chemicals.
Machining safety: ZnSe dust can be hazardous if inhaled — use local exhaust and PPE during grinding/polishing. Collect machining waste per local hazardous waste rules.
Storage: desiccated, padded packaging; avoid moisture exposure and mechanical shocks.
Design & procurement decision checklist
If you need high CW power at 10.6 µm: choose laser-grade CVD ZnSe + HDT coatings + active cooling.
For FLIR windows (8–12 µm): optical ZnSe with appropriate AR coating suffices; consider environmental protective coating.
For spectroscopy: confirm full transmission curve and dispersion across the measurement band.
Example use cases & short case notes
1–3 kW CO₂ cutting heads: CVD ZnSe with HDT AR, water-cooled mount — minimizes window failure and thermal lensing.
Thermal imaging / FLIR: thin ZnSe windows with AR 8–12 µm and hydrophobic coating improve image clarity in outdoor conditions.
FTIR/ATR accessories: ZnSe ATR crystals for organic spectra in 400–4000 cm⁻¹ region (verify chemical compatibility).
Contact & sample request
Ready to evaluate ZnSe for your system? Request sample blanks, coated windows or a custom optic. Our engineers provide LDT pre-screen advice for your laser regime.
Email: sales@supwafer.com
Phone: +86-18059149998
Faqs:
ZnSe is a polycrystalline material with a yellow or reddish-brown cubic crystal system. It is sensitive to air and turns red quickly when exposed to light. It is insoluble in water, has a hardness of only two-thirds that of multispectral ZnS, and a relatively large refractive index.
ZnSe lenses are widely used in spectral analysis, CO₂ lasers, astronomy, medical systems, infrared night vision, thermal imaging, and infrared imaging. It can also be used as a substrate for various optical components.
Yes, ZnSe lenses can be used in laser cutters and CO₂ lasers.
The optical waveband of ZnSe lenses is 0.6 - 20 μm.
ZnSe lenses with AR coatings are available in various thicknesses, such as 3 - 10 μm, 4 - 13 μm, and 10.6 μm.
ZnSe can be electron beam evaporated using a tantalum or molybdenum crucible liner. It is recommended to scan the electron beam at low power to melt the material evenly and avoid drilling holes. The evaporation temperature is approximately 900 °C, and the deposition rate is expected to be 10 - 15 angstroms per second. The substrate surface needs to be cleaned to ensure good adhesion, and if necessary, yttrium oxide (Y₂O₃), hafnium oxide (HfO₂), or fluorides can be used as a thin adhesion layer.
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