UV Air-Spaced Achromatic Doublets, AR-Coated: 245 - 400 nm

  • Minimal Focal Length Shift Over the Design Wavelength Range
  • Air-Spaced Design for Superior Performance and High Power Handling
  • 1" Outer Diameter Aluminum Housing



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

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Wavelength Range 245 - 400 nm
Design Wavelengths 282.5, 325.0, and 367.5 nm
Surface Quality 10-5 Scratch-Dig
(to Prevent Scattering from
High-Power Sources)
Clear Aperture  Ø18 mm
Focal Length Tolerance ±1% at 325.0 nm
Centration <3 arcmin
AR Coating Ravg < 0.5% from 245 - 400 nm
Housing  Ø1" 6061-T6 Aluminum Barrel
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.
Air-Spaced Doublet in a Lens Tube
Click to Enlarge

Air-Spaced Achromatic Doublet in an SM1L30C Slotted Lens Tube with Two SM1RR Retaining Rings


  • Air-Spaced Design Provides Excellent Aberration Performance
  • Ø18 mm Clear Aperture
  • 1" Outer Diameter for Mounting Inside a Ø1" Lens Tube
  • AR Coating for the 245 - 400 nm Range

Thorlabs' Air-Spaced Achromatic Doublets are designed to provide superior spherical and chromatic aberration correction. Air-Spaced Doublets have an optical design with four degrees of freedom. These extra variables allow the performance of these air-spaced doublets to exceed the performance of equivalent cemented doublets in some cases. For details, please see the Performance tab. The air-spaced design is also highly resistant to laser damage, since no cement is utilized in the fabrication process.

The doublets are pre-mounted in an aluminum barrel with tight tolerances on lens and barrel diameter to minimize the effects of lens decentering. Each mount includes an engraving with the part number, AR coating wavelength, focal length, and the direction of light propagation required to collimate a point source. The mount has a 1" outer diameter for mounting inside a Ø1" lens tube (as shown in the photo to the right).

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

Optic Cleaning Tutorial
Optical Coatings and Substrates

UV Air-Spaced Achromatic Doublet Performance

The tables below contains links to pop-ups with plots containing the theoretical performance of each air-spaced achromatic doublet.

Item #Focal Shift PlotsWavefront Error PlotsSpot Radius Plots
ACA254-100-UV 100 mm Focal Shift 100 mm WFE 100 mm Spot Radius
ACA254-150-UV 150 mm Focal Shift 150 mm WFE 150 mm Spot Radius
ACA254-200-UV 150 mm Focal Shift 200 mm WFE 200 mm Spot Radius

Posted Comments:
Suk Hyun Kim  (posted 2024-05-03 20:47:59.867)
I would like to purchase ACA254-200-UV lens. I have three questions. 1. Beam spot size graph is shown. What is the incoming beam diameters? 2. Is the lens diffraction limited? 3. do you offer 300mm focal length lens?
Pawel Czuma  (posted 2019-10-24 14:01:52.707)
Please answer my following questions: 1.) Is It possible to make UV Air-Spaced Achromatic Doublets uncoated? What will be transmission of such doublet from 190 to 400nm? What will be price? 2.) Is it possible to make such UV Air-Spaced Achromatic Doublets uncoated for WD=25mm and focus of approx 33mm? Best Regards, Pawel
YLohia  (posted 2019-10-24 02:30:33.0)
Hello Pawel, thank you for contacting Thorlabs. Custom lenses can be requested by emailing our Tech Support team. We will reach out to you directly to discuss the feasibility of offering this.
saurabh  (posted 2018-03-22 06:08:11.03)
I need this product Qty. 2 Also do you have similar focal lens for f=90mm ?
tfrisch  (posted 2018-03-22 09:47:20.0)
Hello, thank you for contacting Thorlabs. Our Sales Team can send you a quote for 2pcs of ACA254-100-UV, and I will reach out to you directly about price, lead time, and minimum order quantity for a 90mm focal length version.
scottie730318  (posted 2014-05-15 00:57:23.963)
The ACA254-100-UV has any Mounting Thread on the lens housing (i.e. SM1)? thanks
jlow  (posted 2014-05-14 01:29:15.0)
Response from Jeremy at Thorlabs: There's no mounting thread on the lens housing. The outer diameter is Ø1" so you can put this in any mount that can accept Ø1" optics with >0.63" thickness.
scottie730318  (posted 2014-05-15 00:17:31.917)
Each mount includes an engraving with the part number, AR coating wavelength, focal length, and the direction of light propagation required to collimate a point source. It indicated that the direction of arrow go right, the point source must be put in the left to obtain the collimated beam? When the point source put in the left of lens, the collimating beam can be obtained on the right side.
jlow  (posted 2014-05-14 01:28:15.0)
Response from Jeremy at Thorlabs: When the arrow points to the right, the point source should be put on the left for best performance.
user  (posted 2013-02-12 13:23:25.14)
Which is the damage threshold? Thanks
jlow  (posted 2013-02-14 09:58:00.0)
Response from Jeremy at Thorlabs: These lenses are being tested and we will update the website once we have tested values. In the meantime, you could use the value for our -UV coated UVFS window as a guideline, which is 5.0 J/cm^2 (355 nm, 10 ns, 10 Hz, Ø0.350 mm).
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245 - 400 Air-Spaced Achromatic Doublets

Item # f
Air Gapc
ACA254-100-UV 102.9 30.33 -26.88 -25.85 117.77 7.10 6.00 0.25 16.1 85.8 Air-Spaced Doublet Drawing
ACA254-150-UV 150.0 56.55 -24.17 -23.80 Plano 6.35 2.50 0.54 13.0 138.9
ACA254-200-UV 200.005 138.00 -26.56 -25.69 -151.4 4.50 4.25 1.30 13.6 190.0

a. Left lens center thickness in the reference drawing. b. Right lens center thickness in the reference drawing. c. Center air spacing between the lenses.

Item # Transmission Plota Left Lens Materialb Right Lens Materialb
ACA254-100-UV Plot CaF2 UV Fused Silica
ACA254-150-UV Plot CaF2 UV Fused Silica
ACA254-200-UV Plot CaF2 UV Fused Silica
  • The shaded region represents the specified coating range of the lenses. Click here to download transmission data.
  • "Left" and "Right" refer to the orientations of the lenses in the Reference Drawing found by clicking on the info icon above.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
ACA254-100-UV Support Documentation
ACA254-100-UVAir-Spaced Achromatic Doublet, AR Coating: 245 - 400 nm, f=100 mm
ACA254-150-UV Support Documentation
ACA254-150-UVAir-Spaced Achromatic Doublet, AR Coating: 245 - 400 nm, f=150 mm
ACA254-200-UV Support Documentation
ACA254-200-UVAir-Spaced Achromatic Doublet, AR Coating: 245 - 400 nm, f=200 mm