• Brewster-Windows-UV-1

Brewster Windows without Reflection losses of P-Polarization

Brewster Windows are uncoated substrates that can be used in series as polarizers, or to clean up a partially polarized beam. When positioned at Brewster’s Angle, the P-polarized component of the light enters and exits the window without reflection losses, while the S-polarized component is partially reflected. The 20-10 scratch-dig surface quality and λ/10 transmitted wavefront error of our Brewster windows make them an ideal choice for laser cavities.

Brewster windows are typically used as polarizers within laser cavities. When positioned at Brewster’s angle (55° 32′ at 633 nm), the P-polarized portion of the light will pass through the window with no losses, while a fraction of the S-polarized portion will be reflected off the Brewster window. When used in a laser cavity, the Brewster window essentially acts as a polarizer.
Brewster’s angle is given by
tan(θB) = nt/ni
θB is Brewster’s angle
ni is the index of refraction of the incident medium, which is 1.0003 for air
nt is the index of refraction of the transmitting medium, which is 1.45701 for fused silica at 633 nm

Paralight Optics offers Brewster windows are fabricated from N-BK7 (Grade A) or UV fused silica, which exhibits virtually no laser-induced fluorescence (as measured at 193 nm), making it an ideal choice for applications from the UV to the near IR. Please see the following Graph showing reflectance for both S- and P-polarization through UV fused silica at 633 nm for your references.




N-BK7 or UV Fused Silica Substrate

Laser Damage Quantification Test:

High Damage Threshold (Uncoated)

Optical Performances:

Zero Reflection loss for P-Polarization, 20% Reflection for S-Polarization


Ideal for Laser Cavities


Common Specifications:


Reference Drawing for

Brewster Window

The reference drawing to the left shows the reflection of S-polarized light and transmission of P-polarized light through a Brewster window. Some S-polarized light will be transmitted through the window.


Ranges & Tolerances

  • Substrate Material

    N-BK7 (Grade A), UV fused silica

  • Type

    Flat or Wedged Laser 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

    > 90%

  • Parallelism

    Precision: ≤10 arcsec | High Precision: ≤5 arcsec

  • Surface Quality (Scratch - Dig)

    Precision: 60 - 40 | High Precision: 20-10

  • Surface Flatness @ 633 nm

    Precision: ≤ λ/10 | High precision: ≤ λ/20

  • Transmitted Wavefront Error

    ≤ λ/10 @ 632.8 nm

  • Chamfer

    Protected: < 0.5mm x 45°

  • Coating


  • Wavelength Ranges

    185 - 2100 nm

  • Laser Damage Threshold

    >20 J/cm2 (20ns, 20Hz, @1064nm)



♦ The graph to the right shows the calculated reflectance of uncoated UV fused silica for polarized light at various angles of incidence (The reflectance for P-polarized light goes to zero at Brewster's angle).
♦ The index of refraction of UV fused silica varies with wavelength shown in the following left-hand graph (the calculated index of refraction of UV fused silica as a function of wavelength from 200 nm to 2.2 μm).
♦ The following right-hand graph shows the calculated value of θB (Brewster's angle) as a function of wavelength from 200 nm to 2.2 μm when light is passing from air to UV fused silica.


The Index of refraction is Wavelength Dependent


Brewster's Angle is Wavelength Dependent