Click to view item-specific focal length shift data and spot diagrams at various wavelengths.
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.
Molded Glass Aspheric Lenses: 1050 - 1620 nm or 1050 - 1700 nm Broadband AR Coating
Aspheric lenses focus or collimate light without introducing spherical aberration into the transmitted wavefront. For monochromatic sources, spherical aberration often prevents a single spherical lens from achieving diffraction-limited performance when focusing or collimating light. Thus, an aspheric lens is often the best single element solution for many applications including collimating the output of a fiber or laser diode, coupling light into a fiber, spatial filtering, or imaging light onto a detector.
All of these molded glass lenses are also available premounted in non-magnetic 303 stainless steel lens cells that are engraved with the part number for easy identification. These mounted aspheres have a metric thread that makes them easy to integrate into an optical setup or OEM application. The mounted aspheres are readily adapted to our SM1 series of lens tubes by using our Aspheric Lens Adapters. Mounted aspheres can be used as a drop-in replacement for multi-element microscope objectives by combining the lens with our Microscope Objective Adapter Extension Tube.
If an unmounted aspheric lens is being used to collimate the light from a point source or laser diode, the side with the greater radius of curvature (i.e., the flatter surface) should face the point source or laser diode. To collimate light using one of our mounted aspheric lenses, orient the housing so that the externally threaded end of the mount faces the source.
Molded glass aspheres are manufactured from a variety of optical glasses to yield the indicated performance. The molding process will cause the properties of the glass (e.g., Abbe number) to deviate slightly from those given by glass manufacturers. Specific material properties for each lens can be found by clicking on the Glass link in the tables below.
Choosing a Lens
Aspheric lenses are commonly chosen to couple incident light with a diameter of 1 - 5 mm into a single mode fiber. A simple example will illustrate the key specifications to consider when trying to choose the correct lens.
Example: Fiber: P1-630A-FC-2 Collimated Beam Diameter Prior to Lens: Ø3 mm
The specifications for the P1-630A-FC-2, 630 nm, FC/PC single mode patch cable indicate that the mode field diameter (MFD) is 4.3 μm. This specification should be matched to the diffraction-limited spot size given by the following equation:
Here, f is the focal length of the lens, λ is the wavelength of the input light, and D is the diameter of collimated beam incident on the lens. Solving for the desired focal length of the collimating lens yields
Thorlabs offers a large selection of mounted and unmounted aspheric lenses to choose from. The aspheric lens with a focal length that is closest to 16 mm has a focal length of 15.29 mm (Item# 354260-B or A260-B). This lens also has a clear aperture that is larger than the collimated beam diameter. Therefore, this aspheric lens is the best option given the initial parameters (i.e., a P1-630A-FC-2 single mode fiber and a collimated beam diameter of 3 mm). Remember, for optimum coupling the spot size of the focused beam must be less than the MFD of the single mode fiber. As a result, if an aspheric lens is not available that provides an exact match, then choose the aspheric lens with a focal length that is shorter than the calculation above yields. Alternatively, if the clear aperture of the aspheric lens is large enough, the beam can be expanded before the aspheric lens, which has the result of reducing the spot size of the focus beam.
The target values of these constants are available by clicking on the Info Icons below or by viewing the .pdf and .dxf files available for each lens. Links to the files can be found by clicking on the item number in the price tables below.
Aspheric Lens Design Formula
Positive Radius Indicates that the Center of Curvature is to the Right of the Lens
Negative Radius Indicates that the Center of Curvature is to the Left of the Lens
Aspheric Lens Equation
Choosing a Collimation Lens for Your Laser Diode
Since the output of a laser diode is highly divergent, collimating optics are necessary. Since aspheric lenses do not introduce spherical aberration, they are commonly chosen when the collimated laser beam is to be between one and five millimeters. A simple example will illustrate the key specifications to consider when choosing the correct lens for a given application.
Example: Laser Diode to be Used: L780P010 Desired Collimated Beam Diameter: Ø3 mm (Major Axis)
The specifications for the L780P010 laser diode indicate that the typical parallel and perpendicular FWHM beam divergences are 10° and 30°, respectively. Therefore, as the light diverges, an elliptical beam will result. To collect as much light as possible during the collimation process, consider the larger of these two divergence angles in any calculations (i.e., in this case use 30°). If you wish to convert your elliptical beam in to a round one, we suggest using an Anamorphic Prism Pair, which magnifies one axis of your beam.
Ø = Beam Diameter
Θ = Divergence Angle
From the information above, the focal length of the lens can be determined, using the thin lens approximation:
With this information known, it is now time to choose the appropriate collimating lens. Thorlabs offers a large selection of aspheric lenses to choose from. For this application the ideal lens is a -B AR-coated molded glass aspheric lens with focal length near 5.6 mm. The C171TMD-B (mounted) or 354171-B (unmounted) aspheric lenses have a focal length of 6.20 mm, which will result in a collimated beam diameter (major axis) of 3.3 mm. Next, check to see if the numerical aperture (NA) of the diode is smaller than the NA of the lens:
0.30 = NALens > NADiode ≈ sin(15°) = 0.26
Up to this point, we have been using the FWHM beam diameter to characterize the beam. However, a better practice is to use the 1/e2 beam diameter. For a Gaussian beam profile, the 1/e2 diameter is almost equal to 1.7X the FWHM diameter. The 1/e2 beam diameter therefore captures more of the laser diode's output light (for greater power delivery) and minimizes far-field diffraction (by clipping less of the incident light).
A good rule of thumb is to pick a lens with an NA twice of the NA of the laser diode. For example, either the A390-B or the A390TM-B could be used as these lenses each have an NA of 0.53, which is more than twice the approximate NA of our laser diode (0.26). Note that these lenses each have a focal length of 4.6 mm, resulting in an approximate major beam diameter of 2.5 mm.
Posted Comments:
Alberto Carrasco
 (posted 2019-08-30 15:29:47.227)
Single-mode fibers typically have NAs around 0.1. However, all these lenses have much bigger NAs. I understand you can use them to collimate a laser, but I cannot understand how you can use them to focus a collimated laser into a single-mode fiber, because in all cases the NA of the fiber is smaller than the NA of the lens.
nbayconich
 (posted 2019-09-03 12:46:13.0)
Thank you for contacting Thorlabs. Using a lens with a larger NA than a particular fiber with a smaller NA doesn't necessarily mean that you could not focus light into that type of fiber. As long as most of the light that is focused by the collimating lens does not exceed the acceptance angle of the selected fiber, which is determined by the numerical aperture, then you can still couple light into the fiber with relatively high coupling efficiency. The angle that light enters the fiber will be determined by several factors, one being the collimated beam diameter of your source and two the focal length of the selected lens. Reducing the collimated beam diameter will reduce the effective NA of the collimating lens in use, you can estimate NA by using the equation NA=Ø/(2*f).
You will also want to take into consideration the size of the focused spot that will be produced by your collimating lens so that it matches the MFD of the fiber. More information regarding how to calculate the focused spot size can be found under our "Fiber Coupling" tutorial section.
Yitzi Calm
 (posted 2019-07-01 08:13:04.25)
Looking at part # C392TME-C, spec'ed NA = 0.64. If I use: NA = n*a/sqrt(a^2+f^2)
where:
a = 1.8 mm = CA/2
f = 2.75 mm
n = 1 (immersion index)
then I get NA = 0.55.
I understand the formula I used may not be correct. Actually that's the spirit of my inquiry, I'd like to learn what's the correct formula.
Best Regards,
Yitzi
nbayconich
 (posted 2019-07-01 02:11:16.0)
Thank you for contacting Thorlabs, the calculation you provided is useful for thin lenses however cannot be used to accurately determine the NA of an aspheric lens with a high numerical aperture. To get a more accurate value you will have to take the sine of the marginal ray angle. It's easier to see how to calculate this through ray tracing, I will contact you directly to discuss your application.
thha
 (posted 2019-02-21 04:30:41.003)
Hi...
let me know, refletcance value at 650 nm.
about ** %
YLohia
 (posted 2019-02-21 12:10:23.0)
Hello, thank you for contacting Thorlabs. We will reach out with this out-of-range data directly.
hij33153
 (posted 2018-07-07 09:07:49.58)
Hey... What is the spot size at focusing place in the A280TM-C?. Is it okay to understand the rms radius is same with the spot size at focusing place??
YLohia
 (posted 2018-07-09 12:20:26.0)
Hello, the focused spot size depends on the input beam diameter and the wavelength. Please see the spot diameter information we have on this lens here: https://www.thorlabs.com/images/TabImages/A280_Asph.pdf. RMS beam size is just a different way of characterizing a beam size. Alternate ways of characterizing beam size would be 1/e^2, FWHM, etc.
ee14d209
 (posted 2018-02-14 22:57:41.733)
Dear Sir,
We are using C280TMD-C at 1064 nm, can you please let me know the refractive index and extension coefficient of the material used for C280TMD-C.
Thanks,
nbayconich
 (posted 2018-02-23 09:49:05.0)
Thank you for contacting Thorlabs. The material used in C280TMD-C is D-ZK3 which has a refractive index of 1.574 at 1064nm along with an extinction coefficient of 1.6951 x 10^-8 and coefficient of thermal expansion of 7.6 x 10^-6 / °C. I'll reach out to you directly with more information.
m.barrett
 (posted 2017-08-10 13:00:40.207)
What is the damage threshold for the A397TM-C? Thanks
tfrisch
 (posted 2017-08-16 05:53:32.0)
Hello, thank you for contacting Thorlabs. While we don't have any formal damage threshold specs on the molded aspheric lenses, I would expect it to be lower than polished lenses. I will reach out to you directly to discuss the specs of your source.
Do you have the damage threshold of those lenses? Thanks
tfrisch
 (posted 2017-05-16 11:16:42.0)
Hello, thank you for contacting Thorlabs. I will reach out to you directly about your application.
mchen
 (posted 2015-07-14 10:32:57.98)
Do you have the data of C-coating extended to 2 micron? Thanks!
besembeson
 (posted 2015-07-23 04:59:13.0)
Response from Bweh at Thorlabs USA: We don't have data extended to 2um. I will followup with you regarding measuring this.
tcohen
 (posted 2012-04-16 12:49:00.0)
Response from Tim at Thorlabs: The dispersion formula used for these materials is actually the Schott formula. I will contact you with the information including the coefficients and min/max wavelength ranges.
hungwen
 (posted 2012-04-16 03:59:45.0)
Could you also send me the Sellmeier coefficients of these glasses too? (ex: D-ZK3, ECO-550) Thank you!
bdada
 (posted 2012-01-09 19:21:00.0)
Response from Buki at Thorlabs:
The unmounted lens is 352280-1064 and the drawing is linked below. One surface is flat and the other surface is curved outward. Please refer to the drawing linked below for more information and contact TechSupport@thorlabs.com if you have any questions:
http://www.thorlabs.com/Thorcat/19700/19773-E0W.pdf
Hi
Is the C280TME-C lens plano convex/concave? In other words, can I regard it as a thin lens?
Cheers,
Niels.
jjurado
 (posted 2011-03-22 13:38:00.0)
Response from Javier at Thorlabs to clarafly: Thank you very much for contacting us. I will send you this information shortly.
clarafly
 (posted 2011-03-22 18:57:18.0)
Can you provide the Sellmeier coefficients of these glasses so that we can simulate the performance of these lenses? Thanks!
AR Coating Abbreviations
Abbreviation
Description
U
Uncoated: Optics do not have an AR Coating of any kind
A
Broadband AR Coating for the 350 - 700 nm or 400 - 600 nm range
B
Broadband AR Coating for the 600 - 1050 nm or 650 - 1050 nm range
C
Broadband AR Coating for the 1050 - 1620 nm or 1050 - 1700 nm range
V
Narrowband AR Coating designed for the wavelength listed in the table below
The table below contains all molded visible and near-IR aspheric lenses offered by Thorlabs. For our selection of IR molded aspheres, click here. The item # listed is that of the unmounted, uncoated lens. An "X" in any of the five AR Coating Columns indicates the lens is available with that coating (note that the V coating availability is indicated with the design wavelength). The table to the right defines each letter and lists the specified AR coating range. Click on the linked X's to purchase the specific lens, which is available mounted and unmounted.