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
