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Polarizing Bandpass Filter

  • Wavelength Pass Band Only Contains P-Polarization
  • Pass Band Transmission >85%
  • 106:1 Extinction Ratio
  • Center Wavelength at 355 nm


Polarizing Bandpass Filter, CWL = 355 nm

Polarizing Bandpass Filter Mounted in a CM1-DCH Cage Cube Filter Mount

Simplified Operation Drawing

The p-polarization state is passed within the designed pass band, while the s-polarization state is rejected.

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FPB353-15 Specifications
Center Wavelength 355 nm
Bandwidth +6 nm / -9 nm
Extinction Ratioa 1 000 000:1
Optic Size 25.2 mm x 35.6 mm
Optic Thickness 2 mm
Dimensional Tolerance ±0.1 mm
Clear Aperture >21.41 mm x 30.26 mm
Acceptance Angle 45° ± 0.5°
45° ± 7° at 355 nm
Coating Polarizing Bandpass Filter
Transmission (P-Pol., over Bandwidth) >85%
Blocking (Reflection) Regions TP-Pol. 300 - 339 nm: OD > 6
369 - 434 nm: OD > 6
TS-Pol. 300 - 455 nm: OD > 6
Tabs. 434 - 1100 nm: OD > 2
Transmission / OD Datab info
Laser Lines
Surface Quality 60-40 Scratch-Dig
Substrate UV Fused Silicac
Mass 4 g
  • The extinction ratio (ER) is the ratio of maximum to minimum transmission of a sufficiently linearly polarized input. When the transmission axis and input polarization are parallel, the transmission is at its maximum; rotate the polarizer by 90° for minimum transmission.
  • Click on More Info Icon for a plot and downloadable data.
  • Click Link for Detailed Specifications on the Substrate


  • Extinction Ratio: 1 000 000:1
  • 25.2 mm x 35.6 mm x 2.0 mm Unmounted Filter
  • >85% Transmission Within the Pass Band
  • Excellent Suppression in Blocking Regions (OD > 6)
  • UV Fused Silica Substrate
  • 355 nm +6 nm / -9 nm Center Wavelength

Thorlabs' Polarizing Bandpass Filter is designed to isolate key laser lines while also separating out the s- and p-polarization states. The p-polarized component is transmitted over a defined pass band and reflected (rejected) outside of the band, while the s-polarized component is reflected over the entire blocking region of the optic. This filter offers a high extinction ratio of Tp:Ts > 106:1, high p-polarized transmission in the pass band (>85%), and excellent suppression (OD > 6) in the blocking region.

The filter is 25.2 mm x 35.6 mm and has a thickness of 2 mm. It is designed to be used at a 45° AOI; however, when used at the center wavelength, the incident angle can be widened without loss of performance. See the table to the right for details. The item number is engraved on the coated side of the filter, on which we recommend the beam be incident.

The unique design of this filter allows it to be used as a laser line filter, as an analyzer within a DIC microscopy system, or as wavelength selectors within harmonic generation setups or fluorescence imaging systems.

Limited Stock Icon

This item will be retired without replacement when stock is depleted. If you require this part for line production, please contact our
OEM Team.

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. 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.

Non-Polarizing Beamsplitters

Plate Beamsplitters
Cube Beamsplitters
Pellicle Beamsplitters
  • 45° AOI Unless Otherwise Noted

Polarizing Beamsplitters

Plate Beamsplitters
Cube Beamsplitters
Birefringent Crystal Beamsplitters
  • Mounted in a protective box, unthreaded ring, or cylinder.
  • Available unmounted or mounted in a protective box or unthreaded cylinder.

Other Beamsplitters

Other Beamsplitters

Polarizer Selection Guide

Thorlabs offers a diverse range of polarizers, including wire grid, film, calcite, alpha-BBO, rutile, and beamsplitting polarizers. Collectively, our line of wire grid polarizers offers coverage from the visible range to the beginning of the Far-IR range. Our nanoparticle linear film polarizers provide extinction ratios as high as 100 000:1. Alternatively, our other film polarizers offer an affordable solution for polarizing light from the visible to the Near-IR. Next, our beamsplitting polarizers allow for use of the reflected beam, as well as the more completely polarized transmitted beam. Finally, our alpha-BBO (UV), calcite (visible to Near-IR), rutile (Near-IR to Mid-IR), and yttrium orthovanadate (YVO4) (Near-IR to Mid-IR) polarizers each offer an exceptional extinction ratio of 100 000:1 within their respective wavelength ranges. 

To explore the available types, wavelength ranges, extinction ratios, transmission, and available sizes for each polarizer category, click More [+] in the appropriate row below.

Wire Grid Polarizers
Film Polarizers
Beamsplitting Polarizers
alpha-BBO Polarizers
Calcite Polarizers
Quartz Polarizers
Magnesium Fluoride Polarizers
Yttrium Orthovanadate (YVO4) Polarizers
Rutile Polarizers
  • Click on the graph icons in this column to view a transmission curve for the corresponding polarizer. Each curve represents one substrate sample or coating run and is not guaranteed.
  • Mounted in a protective box, unthreaded ring, or cylinder.
  • Available unmounted or in an SM05-threaded (0.535"-40) mount that indicates the polarization axis.
  • Available unmounted or in an SM1-threaded (1.035"-40) mount that indicates the polarization axis.
  • Available unmounted or mounted in cubes for cage system compatibility.
  • Calcite's transmittance of light near 350 nm is typically around 75% (see Transmission column).
  • Available unmounted or in an unthreaded Ø1/2" housing.
  • The transmission curves for calcite are valid for linearly polarized light with a polarization axis aligned with the mark on the polarizer's housing.
  • The 1064 nm V coating corresponds to a -C26 suffix in the item number.
  • Available unmounted or mounted in a protective box or unthreaded cylinder that indicates the polarization axis.

Posted Comments:
stephen.madden  (posted 2018-10-23 00:41:50.483)
Would love to get a version of this at 1030nm centre wavelength on 50x50mm fused silica substrate to match a Yb fibre laser. Is this possible? Could you also please send me a plot of the reflected output for P and S polarisation from 200 to 1000nm please as this is important in the (new) application we are actively developing right now. Many thanks Steve
YLohia  (posted 2018-10-23 08:33:37.0)
Hello Steve, thank you for contacting Thorlabs. I will reach out to you directly to discuss your requirements. Quotes for custom optics can be requested by contacting
igkioule  (posted 2018-06-12 21:41:54.37)
Hi, Is it possible to provide a larger (e.g., 50mm x 50mm or 50mm x 72mm) version of the FPB639-21 beamsplitter? Thank you in advance for the information.
YLohia  (posted 2018-06-13 04:57:59.0)
Hello, we will reach out to you directly via email to look into quoting this further.

Polarizing Bandpass Filter

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
FPB353-15 Support Documentation
FPB353-15Polarizing Bandpass Filter, CWL = 355 nm, Bandwidth = +6 nm / -9 nm
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