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: Uncoated
Aspheric lenses are designed to focus or collimate light without introducing spherical aberration into the transmitted wavefront. For monochromatic sources, spherical aberration is often what 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.
This page features our selection on uncoated molded glass aspheric lenses. Please note that Thorlabs offers a larger selection of aspheric lenses with one of our AR coatings deposited on both sides (see links in the selection table to the right).
All of these molded glass lenses are available premounted in nonmagnetic 303 stainless steel lens cells that are engraved with the part number for easy identification. These mounted versions have a metric thread that makes them easy to integrate into an optical setup or OEM application. Mounted aspheres are readily adapted to our SM1 series of lens tubes by using our Aspheric Lens Adapters. They can be used as a drop-in replacement for multi-element microscope objective 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 Info icons () 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.
Lens Design Formula
Positive Radius Indicates that the Vertex is Located Left of the Center
Negative Radius Indicates that the Vertex is Located Right of the Center
Variable Definitions
z
SAG as a Function of Y
R
Radius of Curvature
k
Conic Constant
A4
4th Order Aspheric Coefficient
A6
6th Order Aspheric Coefficient
A8
8th Order Aspheric Coefficient
A10
10th Order Aspheric Coefficient
A12
12th Order Aspheric Coefficient
Aspheric Lens Coefficients
The aspheric lens coefficients are listed on the product page that is loaded by clicking on the part number in the price table below and in the .pdf and .dxf files available for each lens. Links to the files can be found under the Drawings and Documents tab or by clicking on the part number in the price table below.
Choosing a Collimation Lens for Your Laser Diode
Since the output of a laser diode is highly divergent, collimating optics are necessary. Aspheric lenses do not introduce spherical aberration and are therefore 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)
When choosing a collimation lens, it is essential to know the divergence angle of the source being used and the desired output diameter. 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 into a round one, we suggest using an Anamorphic Prism Pair, which magnifies one axis of your beam.
Ø = Beam Diameter
Θ = Divergence Angle
Assuming that the width of the lens is negligible compared to the radius of curvature, the thin lens approximation can be used to determine the appropriate focal length for the asphere. Assuming a divergence angle of 30° (FWHM) and desired beam diameter of 3 mm:
f = Focal Length
Note that the focal length is generally not equal to the needed distance between the light source and the lens.
With this information known, it is now time to choose the appropriate collimating lens. Thorlabs offers a large selection of aspheric lenses. For this application, the ideal lens is a molded glass aspheric lens with focal length near 5.6 mm and our -B antireflection coating, which covers 780 nm. 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 full-width at half maximum (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 that of the laser diode NA. 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). These lenses each have a focal length of 4.6 mm, resulting in an approximate major beam diameter of 2.5 mm. In general, using a collimating lens with a short focal length will result in a small collimated beam diameter and a large beam divergence, while a lens with a large focal length will result in a large collimated beam diameter and a small divergence.
Posted Comments:
Congli Wang
 (posted 2020-10-03 05:02:59.823)
Same here, A6 coefficient is different on this page (-1.30539e-005) and in the Auto CAD PDF (1.3053900E-05). Which one to trust?
YLohia
 (posted 2020-10-08 03:03:11.0)
Hello, thank you for contacting Thorlabs and bringing this to our attention. The A6 coefficient should have the negative sign. We will correct this information.
Congli Wang
 (posted 2020-10-03 04:50:48.55)
The Aspheric coefficient A6 is not consistent in two different places:
(1) On this page, it is mentioned A6 = -0.0001090000.
(2) However in the AutoCAD PDF, A6 = 1.0900023E-04. (Notice the missing minus sign as well as the last digits)
(2*) If you click on "INFO" on https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3809, you found A6 = 1.0900023 x 10-4, which is consistent with (2).
Which version is correct?
YLohia
 (posted 2020-10-08 03:03:09.0)
Hello, thank you for contacting Thorlabs and bringing this to our attention. The A6 coefficient should have the negative sign. 1.0900023E-04 was rounded down to 0.0001090000. We will correct this information.
Chris Manning
 (posted 2020-08-31 11:29:15.35)
I'm not sure that all the ones I asked for are here, but this is an impressive document that will benefit someone, if only as an example of the densest spreadsheet ever made:
www.hoya-opticalworld.com/common/xls/HOYA20180717.xlsx
Chris Manning
 (posted 2020-08-31 10:29:38.817)
I was wondering about the melting points of these (moldable) glasses and their transmission ranges. I am interested in UV cure. It would be a nice touch if the glass names in the product column were hot links to the glass properties that included transmission ranges, melting points, CTE's, etc.
Hello, thank you for contacting Thorlabs. Our Tech Support China team will reach out to you directly to discuss your request.
AR Coating Abbreviations
Abbreviation
Description
U
Uncoated: Optics Do Not have an AR Coating
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. Clicking on the X takes you to the landing page where that lens (mounted or unmounted) can be purchased.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the focal point.
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the focal point.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the focal point.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the focal point.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the focal point.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the focal point.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the focal point.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture
EFL is specified at the design wavelength for the unmounted lens.
WD is specified at the design wavelength.
This working distance is measured from the back surface of the lens (unmounted) or the back of the housing (mounted) to the front of the window of the laser diode being collimated.
EFL = Effective Focal Length NA = Numerical Aperture CA = Clear Aperture