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BREXIT UPDATE: Knight Optical will continue to provide quality assured service for all your optical requirements both custom & stock. We will handle all requirements caused by the new regulations.


Looking For a Custom Optical Solution? Enquire

Custom Zinc Selenide

Zinc Selenide (ZnSe) is a polycrystalline, semiconductor that readily transmits from 600nm to 21µm, with around 70% transmission between 1-15µm. Produced by chemical vapour deposition (CVD) zinc selenide boasts a lot of impressive properties including:

  • High purity
  • High refractive index homogeneity
  • Chemically inert
  • High damage threshold
  • Insoluble in water
  • Highly resistant to thermal shock
  • Non-hygroscopic
  • Low bulk loss (from absorption and scattering)

Below is a brief summary of Zinc Selenide’s optical properties, a full data sheet is available here.

Transmission range

0.6 to 21µm

Refractive Index

2.4028 @ 10.6µm


5.27 g/cm3

Melting Point



Knoop 120 with 50g indenter

Operating Temperature

< 250°C

Knight Optical supplies high quality zinc selenide components, including windows, lenses and prisms, made to your custom specification. We can offer uncoated and coated optics, including broadband antireflective (BBAR) coatings. Our typical manufacturing specifications are listed below however we are always expanding our capabilities so if your requirements are not mentioned below, please contact our technical sales team who will guide you through your enquiry.


< 5mm to 100mm +

Form error (@633nm)

< 1 wave

Centration /parallelism

< 3 arc minute


< 60/40

Typical coatings

Single sided BBAR @ 2-14µm

With our in-house state-of-the-art metrology laboratory you can be confident that your optical components will meet your requirements. You can find out more about our testing facilities here.

Uncoated, 1mm thick

Additional Information

  • Zinc selenide is a hazardous material and precautions should be taken when handling, please find our Zinc Selenide SDS here.

Typical Applications

CO2 Lasers

  • Laser grade ZnSe infrared lenses are often used as CO2 laser focal lenses as they transmit at 10.6µm, with minimal absorption. It is also the only infrared material which also transmits at 632.8nm which means it works for the CO2/HeNe laser pairing.
  • Zinc selenide beam combiners are also used when a CO2 and HeNe laser are used in conjunction with each other. The beam combiner, positioned at 45° to the CO2 laser, will transmit the CO2 beam (10.6µm) and reflect the HeNe beam (632.8nm) at 45° angle into the path of the CO2 laser beam, combining the two.
  • Zinc selenide resonator windows are used to separate the gas medium from the resonator optics

FLIR and Thermal imaging

  • Zinc selenide optical windows are often used as protective windows in both forward looking infrared (FLIR) and thermal imaging applications. Often these protective windows would have a BBAR coating to reduce the reflection back into the system and maximise the transmission.

Fourier Transform Infrared (FTIR) Spectroscopy

  • Due to zinc selenide’s wide transmission band it is an ideal substrate for attenuated total reflection (ATR) crystals used in FTIR spectroscopy.


Our 2022/2023 Catalogue

Inside Knight Optical’s catalogue you’ll find details of the industries we serve as well as the many other services we can offer. It also showcases hundreds of our most popular products, supported by useful technical information, to help you choose the right part for your application.
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