LWIR Achromatic Doublets Optimized for 7 - 12 µm

  • AR Coating for 7 - 12 µm
  • Design Wavelengths at 8 µm, 10 µm, and 12 µm
  • 1" Outer Diameter Aluminum Housing


f = 50 mm


f = 200 mm

Each mount includes an engraved arrow
indicating the direction of light propagation
required to collimate a point source.

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General Specifications
Antireflection Coating
Ravg < 1.0%, Rabs < 2.0%
from 7 to 12 µm, 0° AOI
Transmissiona Tavg > 97.0%, Tabs > 92.0%
from 7 to 12 µm, 0° AOI
Design Wavelengths 8 µm, 10 µm, and 12 µm
Diameter Ø1" (Ø25.4 mm)
Dimension Tolerance +0.0/-0.1
Centration <3 arcmin
Clear Aperture Ø20.0 mm
Spot Size Diffraction Limited On Axis
Substrates Zinc Selenideb and Zinc Sulfide
Focal Length Tolerance ±1% at 10.6 µm
RMS WFE <λ/10 @ 10.6 µm
Surface Quality 60-40 Scratch-Dig
  • Per Element
  • Click Link for Detailed Specifications on the Substrate


  • Air-Spaced Doublet Design Provides Superior Aberration Performance Compared to Singlet Lenses
  • AR Coated for the 7 - 12 µm Range
  • Designs Incorporate Zinc Selenide (ZnSe) and Zinc Sulfide (ZnS) Substrates
  • Engraved Ø1" Mount for SM1 Compatibility

These AR-coated, air-spaced achromatic doublet lenses provide excellent transmission in the 7 - 12 µm range (surface reflectance for each coating can be seen in the graph to the right). They incorporate two AR-coated lenses, one with a zinc selenide substrate and another with a zinc sulfide substrate. Each achromatic doublet on this page has three design wavelengths: 8 µm, 10 µm, and 12 µm. By optimizing the design for these three wavelengths, the focal shift across the 7 - 12 µm range will be minimized (see the graphs below for details), providing excellent on-axis performance.

Thorlabs' LWIR achromatic doublets are pre-mounted in engraved Ø1" outer diameter mounts, making it easy to incorporate these optics into your setup. Each engraving includes the part number, AR coating range, focal length, an arrow indicating the direction of light propagation to collimate a point source, and an infinity symbol denoting that this lens has an infinite conjugate ratio (i.e., if a diverging light source is placed one focal length away from the flat side of the lens, the light rays emerging from the curved side will be collimated).

Note: We do not recommend disassembly of these lenses, as this may affect performance.

Optic Cleaning Tutorial
Optical Coatings and Substrates
Zemax Files
Click on the red Document icon next to the item numbers below to access the Zemax file download.
Note: ZnSe is a hazardous material. For your safety, please follow all proper precautions while handling any ZnSe products, including wearing gloves and thoroughly washing your hands afterward. For the MSDS for ZnSe in English, click here, and for the MSDS in Japanese, click here.

Posted Comments:
Marina Servol  (posted 2022-10-03 08:41:32.437)
Hello, I have seen your achromatic doublets optimized for 3 - 5 µm and 8 -12 µm. I would like to know if you have a solution for the range 5 - 8 µm. Thanks for your answer. Sincerely, Marina
jdelia  (posted 2022-10-03 02:55:39.0)
Thank you for contacting Thorlabs. Unfortunately, we do not offer any achromatic doublets optimized for this wavelength range. We apologize for the inconvenience. I could certainly pass along your feedback to our engineering team through our internal suggestion forum.
Junyu Li  (posted 2022-01-20 05:58:00.28)
We would like to know the transmission spectrum of the AR coating above 12.5um and below 7.5um
jgreschler  (posted 2022-01-24 04:03:19.0)
Thank you for reaching out to Thorlabs. Additional data can be requested by contacting our Tech Support team at techsupport@thorlabs.com. I have reached out to you directly to provide the requested data.
bdada  (posted 2011-12-20 17:37:00.0)
Response from Buki at Thorlabs: We expect the air spaced doublets to handle up to a linear power density of 35kW/cm. Please contact TechSupport@thorlabs.com if you have any questions.
manuel.uphoff  (posted 2011-12-12 06:26:00.0)
What is the damage threshold of these lenses for a cw CO2-Laser?
jjurado  (posted 2011-08-01 09:24:00.0)
Response from Javier at Thorlabs to nick: Thank you for contacting us. We will send you this information shortly.
nick  (posted 2011-07-25 08:35:22.0)
Can you please provide me with the optical prescription of this lens (radius, aspheric / conic terms, thickness, seperation distance)? Thank you in advance! Nick
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7 - 12 µm Air-Spaced Achromatic Doublets

Item # f
Left Lens
Right Lens
Focal Length Shiftc
AC254-050-E3 50 mm 15.0 mm 37.2 mm Air-Spaced Doublet Drawing Plot Plot Zinc Selenide Zinc Sulfide
AC254-075-E3 75 mm 12.1 mm 65.1 mm
AC254-100-E3 100 mm 11.5 mm 90.5 mm
AC254-200-E3 200 mm 10.0 mm 194.3 mm
  • Click here to download an excel file containing the data shown in the plots above
  • "Left" and "Right" refer to the orientations of the lenses in the drawing found in the Reference Drawing column.
  • Click on for plots and downloadable data of the focal length shift for the lens.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
AC254-050-E3 Support Documentation
AC254-050-E3ZnSe-ZnS Air-Spaced Achromatic Doublet, ARC: 7-12 µm, f = 50 mm
AC254-075-E3 Support Documentation
AC254-075-E3ZnSe-ZnS Air-Spaced Achromatic Doublet, ARC: 7-12 µm, f = 75 mm
AC254-100-E3 Support Documentation
AC254-100-E3ZnSe-ZnS Air-Spaced Achromatic Doublet, ARC: 7-12 µm, f = 100 mm
AC254-200-E3 Support Documentation
AC254-200-E3ZnSe-ZnS Air-Spaced Achromatic Doublet, ARC: 7-12 µm, f = 200 mm