• Single-Surface-Optical-Flats-K9-1
  • Single-Surface-Optical-Flats-UV-1
  • Standard-Flat-Window-K9-1
  • Standard-Flat-Window--UV-1

Precision Flat Optical Windows with or without AR Coatings

Optical windows provide protection between an optical system or sensitive electronics and an outside environment. It is important to select a window that transmits the wavelengths used in the system. In addition the substrate material should be able to withstand the environmental conditions of the application. Windows are useful for protecting a laser output from environmental effects and for beam sampling applications. We offer Windows in a wide range of substrates, sizes and thicknesses to meet any application need.

Paralight Optics offers both standard and high precision optical flat windows fabricated from various substrate materials for use in a large variety of laser and industrial applications. Our substrates include N-BK7, UV Fused Silica (UVFS), Sapphire, Calcium Fluoride, Magnesium Fluoride, Potassium Bromide, Infrasil, Zinc Selenide, Silicon, Germanium, or Barium Fluoride. Our laser windows have a wavelength-specific AR coating centered around commonly used laser wavelengths and an optional wedge, while our precision windows are offered with or without a broadband AR coating providing good optical performance for angles of incidence (AOI) between 0° and 30°.

Here we list Calcium Fluoride Flat Window. Calcium fluoride has a low absorption coefficient and high damage threshold, making these windows a good choice for use with free-space lasers. Our calcium fluoride (CaF2) High-Precision Flat Windows either uncoated or with a broadband anti-reflective coating. The uncoated windows provide high transmission from the ultraviolet (180 nm) to the infrared (8 μm). The AR-coated windows feature an antireflection coating on both sides that provides increased transmission within the 1.65 – 3.0 µm specified wavelength range. Given its low absorption coefficient and high damage threshold, uncoated calcium fluoride crystal is a popular choice for use with excimer lasers. CaF2 windows are also commonly used in cryogenically cooled thermal imaging systems. Please check the following graphs for your references.



Material Options:

See the following flat windows selection

Wavelength Range:

as the requirements

Coating Options:

Available Either Uncoated or AR Coated as Request

Custom Options:

Different Designs, Sizes and Thickness Available


Common Specifications:


This left form is windows selection general guide for your references.


Ranges & Tolerances

  • Substrate Material

    N-BK7 (CDGM H-K9L), UV fused silica (JGS 1) or other IR materials

  • Type

    Standard Flat Window (round, square, etc.)

  • Size


  • Size Tolerance

    Typical: +0.00/-0.20mm | Precision: +0.00/-0.10mm

  • Thickness


  • Thickness Tolerance

    Typical: +/-0.20mm | Precision: +/-0.10mm

  • Clear Aperture


  • Parallelism

    Uncoated: ≤ 10 arcsec | AR Coated: ≤ 30 arcsec

  • Surface Quality (Scratch - Dig)

    Precision: 40-20 | High Precision: 20-10

  • Surface Flatness @ 633 nm

    Typical: ≤ λ/4 | Precision: ≤ λ/10

  • Transmitted Wavefront Error @ 633 nm

    Uncoated: ≤ λ/10 per 25mm | AR Coated: ≤ λ/8 per 25mm

  • Chamfer

    Protected: < 0.5mm x 45°

  • Coating

    Narrow Band: Ravg < 0.25% per surface at 0° AOI
    Broad Band: Ravg < 0.5% per surface at 0° AOI

  • Laser Damage Threshold

    UVFS: >10 J/cm2 (20ns, 20Hz, @1064nm)
    Other Substrate: >5 J/cm2 (20ns, 20Hz, @1064nm)



♦ The graphs show the transmission at normal incidence of our 5 mm thick, uncoated calcium fluoride window, and the reflectance & transmission at normal incidence of our AR-coated CaF2 window for 1.65 - 3.0 µm (Ravg < 1.0% per surface over the range).
♦ We also supply laser windows, which have wavelength-specific AR coatings centered around commonly used laser wavelengths, and Brewster windows, which are used to eliminate P-polarization reflectance. For more information on windows or get a quote, please contact us.


Transmission for 5mm Thick CaF2 Window, AR Coated for 1.65 - 3 µm, at Normal Incidence


Reflectance for 5mm Thick CaF2 Window, AR Coated for 1.65 - 3 µm, at Normal Incidence