Create an Account  |   Log In

View All »Matching Part Numbers

Your Shopping Cart is Empty

MWIR Achromatic Doublets Optimized for 3 - 5 µm

  • AR Coating for 3 - 5 µm
  • Design Wavelengths at 3 µm, 4 µm, and 5 µm
  • 1" Outer Diameter


f = 100 mm


f = 200 mm

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

Related Items

Please Wait
Common Specifications
Diameter Ø1" (Ø25.4 mm)
Dimension Tolerance +0.00/-0.10 mm
Centration <3 arcmin
Clear Aperture  Ø20 mm
Spot Size Diffraction Limited On Axis
Design Wavelengths 3 µm, 4 µm, and 5 µm
Antireflection Coating Ravg < 1.5% from 3 to 5 µm, 0° AOI
Substrates Silicon and Germanium
Focal Length Tolerance ±1% at 4 µm
RMS WFE <λ/10 @ 4 µm
Surface Quality 60-40 Scratch-Dig


  • Air-Spaced Doublet Design Provides Superior Aberration Performance than Singlet Lenses
  • AR Coated for the 3 - 5 µm Range
  • Designs Incorporate Silicon (Si) and Germanium (Ge) Substrates
  • Mounted in Engraved SM1-Compatible Housings

These AR-coated, air-spaced achromatic doublet lenses provide excellent transmission in the 3 - 5 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 germanium substrate and another with a silicon substrate.

Each achromatic doublet on this page has three design wavelengths: 3 µm, 4 µm, and 5 µm. By optimizing the design for these three wavelengths, the focal shift across the 3 - 5 µm range will be minimized (see the graphs below for details), providing excellent on-axis performance.

Thorlabs' MWIR achromatic doublets are pre-mounted in engraved SM1-compatible 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. Our entire Zemax Catalog is also available.
Documents Tab to be Discontinued...
Please note that this tab will be removed at the end of 2015. The same information displayed here can be found by clicking on the red Docs Icon (Support Documentation icon) next to the item of interest in the pricing area below.
Click the Support Documentation icon document icon or Part Number below to view the available support documentation
Part NumberProduct Description
AC254-050-E Support Documentation AC254-050-E:Si-Ge Achromatic Doublet, 50 mm EFL, ARC: 3-5 µm
AC254-075-E Support Documentation AC254-075-E:Si-Ge Achromatic Doublet, 75 mm EFL, ARC: 3-5 µm
AC254-100-E Support Documentation AC254-100-E:Si-Ge Achromatic Doublet, 100 mm EFL, ARC: 3-5 µm
AC254-200-E Support Documentation AC254-200-E:Si-Ge Achromatic Doublet, 200 mm EFL, ARC: 3-5 µm

Please Give Us Your Feedback
Email Feedback On
Contact Me:
Your email address will NOT be displayed.
Please type the following key into the field to submit this form:
Click Here if you can not read the security code.
This code is to prevent automated spamming of our site
Thank you for your understanding.
Would this product be useful to you?   Little Use  1234Very Useful

Enter Comments Below:
Characters remaining  8000   
Posted Comments:
No Comments Posted

3 - 5 µm Air-Spaced Achromatic Doublets

Item #f
Reflectance PlotLeft Lens MaterialaRight Lens MaterialaGraphsb
AC254-050-E5010.040.4Air-Spaced Doublet DrawingPlotSiliconGermanium
  • "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 and transmission 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 / Ships
AC254-050-E Support Documentation
AC254-050-ESi-Ge Achromatic Doublet, 50 mm EFL, ARC: 3-5 µm
AC254-075-E Support Documentation
AC254-075-ESi-Ge Achromatic Doublet, 75 mm EFL, ARC: 3-5 µm
AC254-100-E Support Documentation
AC254-100-ESi-Ge Achromatic Doublet, 100 mm EFL, ARC: 3-5 µm
AC254-200-E Support Documentation
AC254-200-ESi-Ge Achromatic Doublet, 200 mm EFL, ARC: 3-5 µm
Log In  |   My Account  |   Contact Us  |   Careers  |   Privacy Policy  |   Home  |   FAQ  |   Site Index
Regional Websites: West Coast US | Europe | Asia | China | Japan
Copyright 1999-2015 Thorlabs, Inc.
Sales: 1-973-300-3000
Technical Support: 1-973-300-3000

High Quality Thorlabs Logo 1000px:Save this Image