Broad Infrared Use
Useful transmission from approximately 0.4 or 0.6 to 12 µm, depending on grade and processing.
Infrared Optical Material
Zinc Sulfide (ZnS)
Durable Multispectral Performance for Visible and Infrared Systems.
A pale yellow infrared material available in standard and multispectral grades for thermal imaging, defense, aerospace, and harsh-environment windows.
Why Zinc Sulfide
A Durable Infrared Material for Multispectral and Harsh-Environment Optics
Zinc sulfide combines good mechanical durability, broad infrared transmission, and optional visible transmission in multispectral grades.
Multispectral Availability
Special processing can improve visible and near-infrared transmission for multispectral imaging systems.
Good Environmental Durability
Better mechanical durability than ZnSe supports exposed windows and demanding field applications.
Flexible Coating Options
Supports visible, NIR, MWIR, LWIR, dual-band, and protective coating designs.
Engineering Properties
Optical, Mechanical, and Thermal Characteristics
Representative values for optical-grade Zinc Sulfide (ZnS). Final values vary by material grade, wavelength, temperature, thickness, supplier specification, and test method.
Physical & Mechanical Properties
| Chemical Formula | ZnS |
|---|---|
| Crystal Structure | Cubic or hexagonal; optical material is often polycrystalline |
| Density | Approximately 4.09 g/cm³ |
| Knoop Hardness | Approximately 160–220, grade dependent |
| Young’s Modulus | Approximately 74 GPa |
| Poisson’s Ratio | Approximately 0.28 |
| Thermal Expansion | Approximately 6.5 × 10⁻⁶/K |
| Melting / Sublimation | High-temperature behavior is process and grade dependent |
Optical Properties
| Transmission Range | Approximately 0.4/0.6–12 µm, grade dependent |
|---|---|
| Refractive Index | Approximately 2.20 at 10.6 µm |
| Visible Appearance | Pale yellow to cream; multispectral grades may appear clearer |
| Scatter | Standard grade may exhibit more visible scatter than multispectral grade |
| Mechanical Durability | Good for an infrared transmitting material |
| Coating Compatibility | VIS/NIR/MWIR/LWIR AR, dual-band, filter, and protective coatings |
| Available Grades | Standard infrared and multispectral grades |
Optical Transmission
Flexible Transmission for Infrared and Multispectral Imaging
ZnS supports important infrared bands, while multispectral grades extend useful transmission into the visible for combined imaging systems.
Representative only. Final transmission depends on grade, thickness, surface finish, absorption bands, and coating.
Material Comparison
When Zinc Sulfide Is the Best Fit
| Property | Germanium | ZnSe | ZnS | Zinc Sulfide (ZnS) |
|---|---|---|---|---|
| Multispectral Capability | No | No | Visible but softer | Excellent in multispectral grade |
| Mechanical Durability | Good | Very Good | Moderate | Good |
| LWIR Performance | Excellent | Limited | Very Good | Very Good |
| Visible Scatter | Opaque | Opaque | Low | Grade dependent |
| Exposed Windows | Good with coating | Specialized | Limited | Very Good |
Manufacturing Capabilities
From ZnS Blank to Finished Multispectral or Infrared Component
COE Sapphire supports prototype, low-volume, and repeat production of precision ZnS windows, domes, lenses, protective optics, and custom multispectral components.
Precision Machining
Controlled cutting, edging, beveling, coring, and custom geometry fabrication for zinc sulfide.
Optical Polishing
Precision flat, spherical, aspheric, and custom polishing with process control for surface quality and edge integrity.
Optical Coating
MWIR and LWIR anti-reflection, protective, filter, and diamond-like carbon coatings.
Quality Assurance
Dimensional inspection, interferometry, surface inspection, transmission verification, and documentation.
Design Guide
Specify the Right Zinc Sulfide Optical Component
Provide optical grade, operating wavelength, dimensions, tolerances, surface quality, flatness or power, wedge or parallelism, clear aperture, edge treatment, coating, quantity, and environmental requirements.
Discuss Your SpecificationMaterial GradeStandard infrared or multispectral grade
Surface QualityCommercial through precision optical grades
Flatness / PowerApplication-specific interferometric control
Wedge / ParallelismPrecision parallel, wedged, or custom geometry
Edge TreatmentProtective bevel or chamfer recommended for fragile edges
CoatingsUV, VIS, NIR, MWIR, beamsplitter, and custom coatings
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Frequently Asked Questions
Zinc Sulfide (ZnS) Optical Material FAQs
What wavelength range does zinc sulfide transmit?
Depending on grade, ZnS can provide useful transmission from the visible or near infrared to roughly 12 µm.
What is multispectral ZnS?
Multispectral ZnS receives additional processing to improve visible and near-infrared transmission while retaining useful mid- and long-wave infrared performance.
How does ZnS compare with ZnSe?
ZnS is generally harder and more durable, while ZnSe offers lower absorption for CO₂ laser applications and a broader long-wave transmission range.
Is ZnS suitable for exposed windows?
Yes. Its mechanical durability and multispectral availability make it useful for protective windows, sensor apertures, and demanding aerospace or defense environments.
What coatings are available for ZnS?
Options include visible/NIR AR, MWIR/LWIR AR, dual-band, multispectral, filter, and protective coating systems.
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