Precision CVD ZnS Windows for MWIR and LWIR Optical Systems
We manufacture custom ZnS infrared windows for demanding optical systems requiring large clear apertures, precise surface figure, tight parallelism, and high infrared transmission. Our capabilities integrate precision grinding and polishing, ion-assisted AR coating, and optical inspection. We have successfully delivered 400 mm-class ZnS windows, demonstrating our manufacturing capability for large-aperture infrared optics.
Custom ZnS Window Manufacturing Capabilities
We manufacture precision ZnS windows according to customer-specific optical, dimensional, and coating requirements.
| Parameter | Capability / Specification |
| Material | CVD Zinc Sulfide (ZnS) |
| Manufacturing size | 100–400 mm class |
| Proven large-format product | Φ400 mm blank / Φ360 mm clear aperture |
| Thickness | Custom, subject to design review |
| Surface figure | Precision polishing to project-specific tolerances |
| Parallelism | Precision wedge control |
| Surface quality | Imaging-grade finish |
| Coating | MWIR, LWIR, and dual-band AR coatings |
| Inspection | Surface figure, wedge, surface quality, and spectral transmission |
Final specifications depend on aperture, thickness, material grade, and coating requirements. See the demonstrated manufacturing results below.
Proven Manufacturing: 400 mm-Class ZnS Infrared Window
We successfully manufactured and delivered a 400 mm-class ZnS infrared window with a 360 mm clear aperture and 10 mm thickness.
The project required simultaneous control of surface figure, substrate deformation, wedge angle, and dual-band transmission across a large optical aperture.
Verified Specifications
| Parameter | Achieved Result |
| Blank diameter | Φ400 mm |
| Clear aperture | Φ360 mm |
| Thickness | 10 mm |
| Surface figure (PV) | ≤ λ/4 @ 10.6 μm |
| Surface figure (RMS) | ≤ λ/20 @ 10.6 μm |
| Parallelism / wedge | ≤30 arcsec |
| Surface quality | 60-40 scratch-dig |
| MWIR average transmission | ≥95% (3–5 μm) |
| LWIR average transmission | ≥95% (8–12 μm) |
| Angle of incidence | 0°–10° |
| AR coating | Ion-Assisted Deposition (IAD) |
Surface figure specifications apply over the full Φ360 mm clear aperture. The reported transmission performance applies to both spectral bands over the specified AOI range.
Manufacturing Challenges and Solutions
Surface Figure Control on a Thin, Large-Diameter Substrate
With a diameter-to-thickness ratio of 40:1, the window was sensitive to gravity, fixture loading, and polishing-induced deformation. We used segmented support fixtures, controlled polishing pressure, and iterative surface figure correction to maintain the required optical geometry.
Parallelism and Surface Quality
Multi-stage grinding and precision polishing were combined with double-sided correction to minimize subsurface damage and achieve a finished wedge angle of ≤30 arcsec while meeting the specified surface quality.
Dual-Band AR Coating
An IAD dual-band AR coating was applied to achieve average transmission of ≥95% in both the 3–5 μm and 8–12 μm bands over an incidence-angle range of 0°–10°. Coating uniformity and residual stress were managed to limit coating-induced surface deformation.
Final Verification
The completed window underwent surface figure, parallelism, surface quality, and infrared spectral transmission inspection. The manufacturing process included surface figure evaluation before and after coating.
This delivered component demonstrates our ability to integrate large-aperture precision polishing, wedge control, and dual-band coating within a single ZnS optical window.
Precision Manufacturing and Quality Assurance
Our manufacturing process focuses on the optical and mechanical factors that become increasingly critical as aperture increases.- Material evaluation: Incoming CVD ZnS inspection, including optical uniformity and residual-stress considerations.
- Precision polishing: Controlled grinding, subsurface damage removal, and surface figure correction.
- Large-aperture support: Fixture and process design to minimize gravity- and clamping-related deformation.
- AR coating: IAD coating with attention to spectral performance, thickness uniformity, and coating stress.
- Optical inspection: Surface figure, wedge, surface quality, and spectral transmission verification.
Applications
Our custom ZnS windows support demanding infrared optical assemblies, including:- MWIR and LWIR imaging systems
- Large-aperture infrared sensing and observation systems
- Airborne and maritime electro-optical equipment
- Infrared search and tracking systems
- Scientific and industrial infrared instrumentation
Custom ZnS Window Engineering Support
For large-diameter ZnS windows, aperture, thickness, mounting conditions, surface figure, and coating requirements must be evaluated together.
We work with optical engineers to review manufacturing feasibility and establish appropriate processing and inspection requirements.
For technical evaluation or quotation, please provide the available specifications:
- Blank diameter, clear aperture, and thickness
- ZnS material grade
- Surface figure or transmitted wavefront error requirements
- Parallelism / wedge tolerance
- Surface quality and applicable standard
- Operating wavelength bands, transmission targets, and AOI range
- Mounting and environmental requirements
- Quantity and inspection documentation
Request a Custom ZnS Infrared Window
Need a precision ZnS window with challenging dimensional, optical, or coating requirements?
Submit your drawing or technical specifications for a manufacturability review and quotation.
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