CO₂ Laser Windows

Our CO2 laser windows are made from Laser Grade ZnSe and coated with low absorbing and low reflectance coatings. Windows from other materials such as Germanium, Silicon, Zinc Sulphide (ZnS) can also be made and coated for other wavelengths.

ZnSe windows can be fabricated in dimensions from 5.0 mm to 300 mm diameter, and in thicknesses from 1.0 mm up to 50 mm (related to diameter and pressure differential). Many standard sizes are manufactured and held in stock. Square and rectangular ZnSe windows can be fabricated to order.

Brewster Windows

Brewster windows operate at an angle of incidence equal to the ‘Brewster angle’ which is 67.4 degrees for ZnSe at 10.6mm. In order to present a square profile to the incident beam, they are about 2.5 times longer than their width. They fully transmit linearly polarized light in the P-plane and reflect about 50% of the S-plane component. Consequently, they can be used to enhance (‘clean-up’) the polarization or by rotating it about the beam axis, they can be used as an attenuator. Coated versions enhance the reflectance of the S-component but at the expense of restricting the power. Usually, Brewster windows are used in pairs.

  • Wedged to between 3 and 5 arcminutes in order to overcome multiple interference
  • Coated or uncoated versions and many sizes available
  • Also available in matched wedge pairs


The following Brewster windows are currently available.  Others may be available upon request

Part No Material Diameter ET Coating
ZBW2510 ZnSe 25mm 3mm Uncoated ZnSe
ZBW3315 ZnSe 33mm 3mm Uncoated ZnSe
EZBW4015 ZnSe 40mm 3mm AR/U-EB
ZBW4218 ZnSe 42mm 3mm Uncoated ZnSe
ZBW5018 ZnSe 50mm 3mm Uncoated ZnSe
EZBW5018 ZnSe 50mm 3mm AR/U-EB
ZBW5320 ZnSe 53mm 3mm Uncoated ZnSe
Part No Material Diameter ET Coating
ZBW6122 ZnSe 61mm 3mm Uncoated ZnSe
ZBW6323 ZnSe 63mm 3mm Uncoated ZnSe
ZBW6625 ZnSe 66mm 3mm Uncoated ZnSe
EZBW6625 ZnSe 66mm 3mm AR/U-EB
ZBW10038 ZnSe 100mm 3mm Uncoated ZnSe
ZBW11542 ZnSe 115mm 3mm Uncoated ZnSe
ZBW13248 ZnSe 132mm 3mm Uncoated ZnSe


ULO Optics is the leading European manufacturer of laser optics, a position held for more than two decades. The optics manufactured by ULO are often used in high power laser systems and have always been designed for such environments. Apart from optimum design and manufacturing standards, the key to the success of any optic relates to the coating performance.

A wide range of coatings are available for our products.

  • AR coatings for lenses and windows include standard AR, UltraLO AR, Dual-Band AR, Broad & Wide-Band AR and diamond-like carbon (DLC) AR. The AR coatings can be tailored for your specific wavelengths as needed. And special coating is available for Brewster windows which enhances the difference in S and P reflectance/transmittance.
  • Special coatings for 9.3 um and 9-11 um available.
  • Mirrors can be Supermax R, NiCu Gold, and Gold coated copper. Phase retarders are available on copper and silicon. We also offer a specialized coating for polarization forcing mirrors.
  • Partial reflectors are available from 0.75% to 99.9%, plus a polarization-insensitive 50:50 beam splitter as well as beam combiners.

Ultra-Lo Coatings

UltraLO optics are specifically fabricated for use in the growing family of CO2 high power lasers. The total lens absorption of the UltraLO coating is significantly less than < 0.15% at 10.6 microns. Typically the results from 2014 measured 0.10% on 9mm thick parts.

UltraLO lenses will handle the same high power as conventional lenses but with less optical distortion and a smaller focal length shift due to less heating of the substrate. Additionally, the lower absorption of the UltraLO lenses can lead to longer lens lifetime.


  • Lower thermal effects in optics at high power

Supermax R Coatings

Supermax R coated mirrors offer exceptional performance  with high reflectivity. The Supermax R coating offers high durability, withstanding the MIL-Spec severe abrasion test making them easily cleaned, leading to longer mirror lifetime. Every Supermax R optic, in addition to its other high performance characteristics, also provides zero phase shift (+/- 2°) at 10.6 microns.

Supermax coated silicon mirrors are the ideal choice for a variety of applications, from beam path fold mirrors to lightweight scanner mirrors. Supermax copper mirrors can also be used for various functions such as fold mirrors, zero phase optics and intracavity mirrors, giving the user outstanding performance without compromise.


  • Zero phase retardation
  • >99.8% average reflectance
  • Rs = 99.93%, Rp = 99.81%
  • Absorption at normal incidence = 0.11%.
  • ThF4 free

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