The engraving on the housing is parallel to polarized transmitted light and perpendicular to the orientation of the wires.
Features
Polarize Light from 3 - 5 µm or 7 - 15 µm
Extinction Ratio:
3 - 5 µm (-IRA): >1000:1
7 - 15 µm (-IRC): >10 000:1
Offered in Four Sizes
Ø25.0 mm
12.5 mm x 12.5 mm
25.0 mm x 25.0 mm
50.0 mm x 50.0 mm
Anodized Aluminum Mount with Transmission Axis Indicated
The mounted wire grid polarizers on silicon substrates sold here are designed to provide high extinction over two spectral ranges in the mid-IR: 3 - 5 µm (3333 - 2000 cm-1) or 7 - 15 µm (1429 - 667 cm-1). The 3 - 5 µm versions (denoted by -IRA) offer >1000:1 extinction and >85% average transmission over their specified range, while the 7 - 15 µm versions (denoted by -IRC) offer >10 000:1 extinction and >75% average transmission over their specified range. Wavelength-dependent plots of the transmission are available in the Specs tab. The polarizers are recessed inside Ø25.0 mm, 12.5 mm square, 25.0 mm square, or 50.0 mm square mounts fabricated from anodized aluminum. As shown by the drawings to the right, the mounts are engraved with the polarization axis of the transmitted light.
These MIR polarizers consist of a linearly spaced wire grid pattern that is deposited onto an AR-coated silicon substrate. Silicon was chosen because it offers good transmission in the mid-IR wavelength range. Because the wire grid absorbs and reflects radiation that is polarized parallel to the grid, the polarization of the transmitted radiation is perpendicular to the wires. These polarizers feature a mark on the housing to indicate the transmission axis (see diagrams to the right).
For smooth attenuation over the specified wavelength range and fine control over the output polarization direction, we recommend the Ø25.0 mm versions, which are well suited for use with our family of rotation mounts for Ø1" optics. The 12.5 mm square, 25.0 mm square, and 50.0 mm square versions can be secured in a cylindrical lens mount. Since our cylindrical lens mounts do not provide rotation, the square polarizers are best for applications that only require horizontal or vertical polarization.
The surface of a wire grid polarizer, like any diffraction grating, is extremely delicate. Never touch the surface of the polarizer, and only handle it by the edge. Careful removal of dust by gentle air flow is the only recommended cleaning procedure.
For broadband applications in the MIR, Thorlabs offers holographic wire grid polarizers for the 2 - 30 µm spectral range. In addition, we have wire grid polarizers on glass substrates for the 250 nm - 4 µm spectral range, which help enable the use of a visible alignment beam in a mid-IR experiment. For our complete selection of polarizers, please see the Polarizer Guide tab.
Item #
WP12LM-IRA
WP25M-IRA
WP25LM-IRA
WP50LM-IRA
WP12LM-IRC
WP25M-IRC
WP25LM-IRC
WP50LM-IRC
Wavelength Range
3 - 5 µm (3333 - 2000 cm-1)
7 - 15 µm (1429 - 667 cm-1)
Extinction Ratioa
>1000:1 Over Entire Wavelength Range
>10 000:1 Over Entire Wavelength Range
Transmissionb
>85% (Average) Over Wavelength Range
>75% (Average) Over Wavelength Range
Housing Size
12.5 mm x 12.5 mm
Ø25.0 mm
25.0 mm x 25.0 mm
50.0 mm x 50.0 mm
12.5 mm x 12.5 mm
Ø25.0 mm
25.0 mm x 25.0 mm
50.0 mm x 50.0 mm
Housing Thickness
5.8 mm
5.8 mm
5.8 mm
5.8 mm
5.8 mm
5.8 mm
5.8 mm
5.8 mm
Clear Aperture
6.0 mm x 6.0 mmc
Ø19.0 mm
18.0 mm x 18.0 mmc
42.0 mm x 42.0 mmc
6.0 mm x 6.0 mmc
Ø19.0 mm
18.0 mm x 18.0 mmc
42.0 mm x 42.0 mmc
Transmission Axis Accuracyd
±2°
Angle of Incidence
±20°
Distance Between Wires
144 nm
Wire Thickness
65 nm
Thermal Expansion
2.6 x 10-6 per °C
Substrate
AR-Coated Silicon
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.
Specified at normal incidence for light polarized parallel to the transmission axis of the polarizer.
As shown by the drawing below, our square mid-IR polarizers have rounded corners that slightly reduce the clear aperture of the optic.
With respect to the engraved line on the housing, as shown in the drawings below.
Engraving is Parallel to Transmitted Light Polarization
Click to Enlarge Excel Spreadsheet Containing Raw Data Extended-Range Transmission of 3 - 5 µm Polarizers The shaded region in this graph denotes the range over which these polarizers provide >1000:1 extinction.
Click to Enlarge Excel Spreadsheet Containing Raw Data Extended-Range Transmission of 7 - 15 µm Polarizers The shaded region in this graph denotes the range over which these polarizers provide >10 000:1 extinction.
Posted Comments:
Alex Sabella
 (posted 2020-07-28 02:26:50.743)
Hi,
Do you have CW damage thresholds for the MIR polarisers on silicon (e.g WP25LM-IRA) or the holographic wire grid polariser (e.g. WP25H-B).
Thank you,
Alex
YLohia
 (posted 2020-07-30 02:38:12.0)
Hello Alex, thank you for contacting Thorlabs. As per our direct discussion, your beam parameters of 4.8um 2W (2 mm x 3 mm) will be fine to use with the WP25LM-IRA.
Martin Svoren
 (posted 2020-05-27 03:22:21.777)
Hey Thorlabs,
we are missing threshold damage information. could you tell us?
Thank you and best regards
Martin
YLohia
 (posted 2020-07-14 02:03:30.0)
Hello Martin, thank you for contacting Thorlabs. Could you please tell us your beam parameters (Wavelength, average power, peak power, pulse width, and repetition rate)? I had reached out to you at the time of your posting but I never heard back. Please email us at techsupport@thorlabs.com if you have further questions.
georg.ramer
 (posted 2018-10-11 18:06:16.153)
What is the extinction ratio of the IRC wiregrid polarizers outside the specified transmission range of 7 to 15 um?
YLohia
 (posted 2018-10-15 10:34:32.0)
Hello, thank you for contacting Thorlabs. The transmission in the 2-16um extended range is given in the Specs tab.
hasal
 (posted 2014-12-08 12:43:40.217)
Hello, can you tell me which value of extinction ration is related to the WP12LM-IRA? Do you offer all of the listed types in two variations with 1:1000 and 1:10 000? Thanks for explanation.
myanakas
 (posted 2014-12-08 08:54:22.0)
Response from Mike at Thorlabs: Thank you for your feedback. The extinction ratio for the WP12LM-IRA is >1000:1. This can be found in the table on the "Specs" tab or on the support drawing, which can be found by clicking on the red "Decs" icon next to the part number (http://www.thorlabs.de/thorcat/TTN/WP12LM-IRA-AutoCADPDF.pdf). Part numbers ending in -IRA have an extinction ration of >1000:1 and part numbers ending in -IRC have an extinction ratio of >10000:1. We will work to make this more clear on the webpage.
Will WP25M-IRA pass a decent fraction of light at 650nm? I just want to make sure our pointing lasers will still be visible after passing through two or three of these (assuming the pointing laser is correctly polarized to pass through). Thanks.
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.
9.1 mm x 9.5 mm x 9.5 mmb and 10.7 mm x 15.9 mm x 15.9 mmb
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.