Brewster Windows
![](https://www.thorlabs.com/Images/GuideImages/919_BrewsterWindows_5.jpg)
- Uncoated UV Fused Silica Brewster Windows
- Parallelism: ≤5 arcsec
- Zero Reflection Loss for P-Polarized Light
BW0801
BW1602
BW0601
BW2502
![](../../images/loading-red.gif)
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![UVFS Brewster Angle](https://www.thorlabs.com/images/TabImages/UVFS_Brewster_Reflectance_G1-300.gif)
Click to Enlarge
This graph 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.
Features
- Ideal for Laser Cavities
- UV Fused Silica Substrate
- Available Minor Diameters: 6 mm, 8 mm, 13 mm, 16 mm, 20 mm, and 25 mm
- P-Polarized Light is Transmitted without Reflection Losses
- Brewster Window Mounts Available
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 graph to the right shows reflectance for both S- and P-polarization through UV fused silica at 633 nm. 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.
These Brewster windows are manufactured from 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 Graphs tab for a transmission plot of UV fused silica. Since the index of refraction of UV fused silica varies with wavelength, Brewster's angle is wavelength dependent; the Graphs tab also contains details on this dependence.
We offer mounting options for 8 mm, 13 mm, 16 mm, 20 mm, and 25 mm minor diameter Brewster windows. These mounts are engineered with a 55° 32’ mounting angle (Brewster’s Angle at 633 nm) with an exit port for the reflected S-polarized light so that the mount may be used in either direction.
We also offer a Brewster Window View Port for use in vacuum systems and Empty Glass Cells with Brewster Windows for spectroscopy applications. In addition to Brewster windows, Thorlabs also offers High Precision Windows, Narrowband Laser Windows, and a complete line of polarization optics.
UV Fused Silica Transmission, Index of Refraction, and Brewster's Angle
![UVFS Brewster Angle](https://www.thorlabs.com/images/TabImages/UVFS_Brewster_Reflectance_G1-350.gif)
Click to Enlarge
This graph shows the calculated reflectance of uncoated UV fused silica for polarized light as a function of angle of incidence. The reflectance for P-polarized light goes to zero at Brewster's angle.
![UVFS Brewster Angle](https://www.thorlabs.com/images/TabImages/Uncoated_1mm_UVFS_Transmission_370.gif)
Click to Enlarge
This graph shows the transmission of a 1 mm thick UV fused silica sample, including surface reflections, with the incident light normal to the surface.
![UVFS Index of Refraction](https://www.thorlabs.com/images/TabImages/UVFS_n_G1-350.gif)
Click to Enlarge
This graph shows the calculated index of refraction of UV fused silica as a function of wavelength from 200 nm to 2.2 μm.
![Brewster Angle for Air to UVFS](https://www.thorlabs.com/images/TabImages/UVFS_Brewster_Angle_G1-350.gif)
Click to Enlarge
This graph shows the calculated value of Brewster's angle as a function of wavelength when light is passing from air to UV fused silica.
The index of refraction for UV fused silica is wavelength dependent, as shown in the graph above, and expressed by the following formula:
.
Please note that that the wavelength needs to be in microns when using the formula above. Brewster's angle is given by
.
Here, θB is Brewster's angle, ni is the index of refraction of the incident medium (1.0003 for air), and nt is the index of refraction of the transmitting medium (1.45701 for fused silica at 633 nm). Hence, Brewster's angle also displays a wavelength dependence, as shown in the plot above.
![Polarization through a Brewster Window](https://www.thorlabs.com/images/TabImages/Brewster_Windows_D1-300.gif)
The image above 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.
Brewster Windows
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
![Brewster's Angle Equation](https://www.thorlabs.com/images/TabImages/BW_equation.gif)
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
It should be noted that the index of refraction is wavelength dependent. For fused silica, the index of refraction can be expressed as
![Index of Refraction for Fused Silica wavelength dependency](https://www.thorlabs.com/images/TabImages/BW_n_equation.gif)
Please note that that the wavelength needs to be in microns when using the formula above.
Posted Comments: | |
m lieb
 (posted 2023-11-30 13:51:35.523) Hi,
am I assuming correctly that only one of the "edges" of the window has a bevel whereas the other one is "pointy"?. I would like to transmit as close as possible to the edge cdolbashian
 (posted 2023-12-15 09:15:31.0) Thank you for reaching out to us with this inquiry. The obtuse angles of this element have no bevel, while the acute angles have a small bevel. I have contacted you directly with a drawing which will, hopefully, be helpful for clarity. prathmesh ghag
 (posted 2022-04-22 16:04:17.86) For BW 2502 the transmission wavefront error is λ/10.
Kindly let me know the transmission wavefront error specification offered for this product. jdelia
 (posted 2022-05-16 04:08:47.0) Thank you for contacting Thorlabs. Like you mentioned, we specify the transmitted wavefront error as <λ/10. I have contacted you directly to clarify your inquiry further Ramon.alvarez
 (posted 2018-05-14 20:58:04.127) What is the roughness of you elliptical Brewster windows? YLohia
 (posted 2018-05-15 10:10:42.0) Hello, thank you for contacting Thorlabs. While we do not have an official specification for the surface roughness for these units, it is typically on the order of < 5 Å. dt_m0hammed_temimi
 (posted 2016-08-21 11:19:12.747) please I need a brewster window with amount using with intracavity Nd:YAG laser jlipa
 (posted 2013-10-25 14:36:32.427) I need some Brewster windows like BW1602, but made from IR grade fused silica. Can you supply them? tcohen
 (posted 2013-10-29 13:11:00.0) Response from Tim at Thorlabs: Yes, we can quote this. We will contact you to discuss your requirements. jack
 (posted 2009-05-26 15:21:13.0) Response from Jack at Techsupport: If you look at the surface at 0 deg. then youll see a circular surface, at any other angle the surface will appear to be elliptical.
The models are fine but the front view in drawing needs to be corrected. Optic department has been informed. csandberg
 (posted 2009-05-26 05:24:03.0) The solid model for these brewster windows seem to be wrong.
The flat surfaces of the window should be elliptical when viewed perpendicular, and circular when viewed from the brewster angle.
PS. Also see Lars Sandtroms comment on BW0601 earlier. It goes for all windows in this section. lsandstrom
 (posted 2009-05-26 02:34:45.0) BW0601 seems to be associated with the wrong SolidWorks model.
The front surface of the model is circular in the Solid model while elliptical on the real device. Laurie
 (posted 2009-05-01 13:36:20.0) Response from Laurie at Thorlabs to egualda: Thank you for your interest in our Brewster Windows. At this time, we do not carry a standard mount for these optics. However, I have emailed a member of our mechanics unit to see if he has any ideas that we can share with you or any previous prototypes that may work. egualda
 (posted 2009-04-30 11:16:20.0) Do you have any spetial holder for the following item: BW0801 Brewster Window, 8mm diameter 1 mm thickness? |
Beamsplitter Selection Guide
Thorlabs' portfolio contains many different kinds of beamsplitters, which can split beams by intensity or by polarization. We offer plate and cube beamsplitters, though other form factors exist, including pellicle and birefringent crystal. For an overview of the different types and a comparison of their features and applications, please see our overview. Many of our beamsplitters come in premounted or unmounted variants. Below is a complete listing of our beamsplitter offerings. To explore the available types, wavelength ranges, splitting/extinction ratios, transmission, and available sizes for each beamsplitter category, click More [+] in the appropriate row below.Plate Beamsplitters
Non-Polarizing Plate Beamsplitters |
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Polarizing Plate Beamsplitters |
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Cube Beamsplitters
Non-Polarizing Cube Beamsplitters |
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Polarizing Cube and Polyhedron Beamsplitters |
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Pellicle Beamsplitters
Non-Polarizing Pellicle Beamsplitters |
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Crystal Beamsplitters
Polarizing Crystal Beamsplitters |
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Other
Other Beamsplitters |
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Item # | BW0601 | BW0801 | BW0802 | BW1302a | BW1602 | BW2002 | BW2502 |
---|---|---|---|---|---|---|---|
Minor Diameter | 6.0 mm | 8.0 mm | 8.0 mm | 13.0 mm | 16.0 mm | 20.0 mm | 25.0 mm |
Minor Diameter Tolerance | +0.00 / -0.10 mm | ||||||
Thickness | 1.0 mm | 2.0 mm | |||||
Thickness Tolerance | ±0.1 mm | ±0.2 mm | ±0.1 mm | ||||
Brewster Angle | 55° 32' @ 633 nm | ||||||
Clear Aperture | >90% of Minor Axis | ||||||
Parallelism | ≤5 arcsec | ||||||
Transmitted Wavefront Errorb | <λ/10 | ||||||
Surface Quality | 20-10 Scratch-Dig | ||||||
Wavelength Range | 185 nm - 2.1 μm (Uncoated) | ||||||
Substrate | UV Fused Silicac | ||||||
Transmission Data | ![]() |
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These Brewster Window Optic Mounts are designed with steel flexure retention plates for holding the optics in place. The mounts feature a separate mounting surface for compatibility with Ø1/2" or Ø1" smooth bore mounts or internally SM1-threaded components. The exit port for the reflected S-polarized light allows the mount to be used in either direction. For more information, please see our full presentation here.
Brewster Window Mount Item # | Mounting Surfacea | Compatible Brewster Window | ||
---|---|---|---|---|
Minor Diameter | Thickness | Brewster Window Item # | ||
BW08M1 | Ø1/2" Smooth Bore | 8 mm | 1 mm | BW0801 |
BW08M2 | 8 mm | 2 mm | BW0802 | |
BW13M | Ø1" Smooth Bore | 13 mm | 2 mm | BW1302 |
BW16M | 16 mm | 2 mm | BW1602 | |
BW20M | 20 mm | 2 mm | BW2002 | |
BW25M | External SM1 | 25 mm | 2 mm | BW2502 |