Common Beam Expander Features

Ideal for Reducing Beam Divergence
Diffraction-Limited Performance with <λ/4 Wavefront Error Introduced
Input Aperture is Threaded to Work with our SM05- and SM1-Threaded Adapters
Easy to Mount and Align using our Standard Posts and Mounts

These Galilean Beam Expanders provide an ideal solution for expanding or reducing beam diameters. Beam expanders are commonly used to reduce divergence. Another common use is to expand the beam and then focus with another lens to take advantage of a reduction in spot size. These beam expanders have all been designed to minimize the telescope length, minimize the introduced wavefront error (<λ/4), and provide diffraction-limited performance (for <Ø1 mm input).

The design incorporates a plano-concave singlet to provide the desired divergence and a doublet, which has been computer optimized to balance aberrations and re-collimate the beam. The rotary barrel controls adjustment of the diverging lens with graduations in 50 µm increments. All of the designs are available with a broadband antireflection coating for the 400 - 650 nm (-A), 650 - 1050 nm (-B), or 1050 - 1620 nm (-C) wavelength range.

Thorlabs also offers many other types of beam expanders, including variable beam expanders whose expansion ratio is achieved via rotation and fixed beam expanders with a sliding collimation adjustment mechanism. For more information on our extensive line of beam expanders, please click on the Selection Guide tab.

Easy Mounting and Alignment

The new BE series of beam expanders now come with an improved design for easier mounting and alignment (see photos below). The input aperture has been threaded to provide compatibility with our externally threaded SM05 (for BE02M, BE03M, and BE05M) or SM1 (BE10M, BE15M, and BE20M) products. As a result, these beam expanders are able to be used with any of our standard adapters, lens holders, iris diaphragms, etc.

The image to the right shows the beam expander mounted in a KM100 kinematic mount. A mounting ring allows the beam expander to be secured into 1" or 2" mounts. BE02M, BE03M, and BE05M can be used with our KS1, KM100, or FMP1. BE10M, BE15M, and BE20M have 2" mounting ring to be used with our KS2 or FMP2.

The image to the left shows the new mounting configuration available with all BE series beam expanders. 4-40 and M3 tapped holes are provided on the BE02M, BE03M, and BE05M, while the BE10M, BE15M, and BE20M models have 8-32 and M4 tapped holes.

	BE02M	BE03M	BE05M	BE10M	BE15M	BE20M
Expansion	2X	3X	5X	10X	15X	20X
Input Aperture	Ø8.0 mm	Ø8.0 mm	Ø4.5 mm	Ø4.5 mm	Ø4.5 mm	Ø4.5 mm
Max. Input Beam Diameter^a	Ø4.0 mm	Ø4.5 mm	Ø2.5 mm	Ø2.0 mm	Ø1.6 mm	Ø1.2 mm
Input Thread	SM05	SM05	SM05	SM1	SM1	SM1
Output Thread	SM1	M36^b	M36^b	SM2	SM2	SM2
Recommended Mount	KS1 / MSP1	KS1 / MSP1	KS1 / MSP1	KS2 / TR2	KS2 /TR2	KS2 / TR2
AR Coating Options	-A: 400 - 650 nm -B: 650 - 1050 nm -C: 1050 - 1620 nm
Scratch-Dig	20-10
Wavefront Error	<λ/4
AR Coating Reflectivity	<0.5% over AR Coating Range
Lens Substrates	N-BK7, SF2	N-BK7, N-SK11	N-BK7, N-SK11	N-BK7, SF2	N-BK7, N-SF5	N-BK7, N-SF5
Housing Dimensions
Input Housing Dimension	Ø23.5 mm			Ø32.0 mm
Output Housing Dimension	Ø31 mm	Ø40.0 mm	Ø42.0 mm	Ø56.0 mm	Ø59.0 mm	Ø59.0 mm
Length of Housing	38 - 42 mm	67 - 72 mm	71 - 79 mm	116 - 136 mm	197 - 215 mm	267 - 287 mm

^aFor Diffraction-Limited Performance
^bThe SM2A19 adapter, shown below, makes these beam expanders compatible with our Ø2" Lens Tubes and 60 mm Cage Systems. It features external M36 threads and internal SM2 threads.

Thorlabs offers several different families of beam expanders to meet various experimental needs. The table below provides a direct comparison of the options we offer. Please feel free to call one of our applications engineers if you would like help choosing the best beam expander for your specific application.

Specification	ELU Series	EL Series	ELQ Series	BE Series (Fixed)	BE Series (Variable, Rotation)	BE Series (Variable, Sliding)	BE Series (Reflective)
Expansions Available	2.5X, 5X, 10X, 20X	2.5X, 3X, 5X, 10X, 20X	2.5X, 5X, 10X, 20X	2X, 3X, 5X, 10X, 15X, 20X	2-5X 5-10X	0.5 - 2X	2X, 4X
Collimation Adjustment Mechanism	Sliding			Rotation		Sliding	Fixed
AR Coating Range(s) Available	248 nm 351 nm	400 - 650 nm 650 - 1050 nm 1050 - 1620 nm 3000 - 5000 nm	1064 ± 40 nm	400 - 650 nm 650 - 1050 nm 1050 - 1620 nm		400 - 650 nm 650 - 1050 nm	None
Mirror Coating (Range)	None						Silver (450 nm - 20 μm)
Average Reflectivity (per Surface)	<0.2%	<2%	<0.2%	<0.5%		<0.5%	>96%
Max Input Beam Diameter (1/e²)^a	2.5X: Ø4.4 mm 5X: Ø2.2 mm 10X: Ø1.1 mm 20X: Ø0.6 mm	2.5X: Ø4.4 mm 3X: Ø4.0 mm 5X: Ø2.2 mm 10X: Ø1.1 mm 20X: Ø0.6 mm	2.5X: Ø4.4 mm 5X: Ø2.2 mm 10X: Ø1.1 mm 20X: Ø0.6 mm	2X, 3X: Ø4.0 mm 5X, 10X, 15X, 20X: Ø2.25 mm	Ø3.0 mm	0.5X: Ø6.0 mm to 2X: Ø3.0 mm	Ø3 mm
Input Aperture	2.5X: Ø9 mm 5X: Ø10.9 mm 10X: Ø9 or Ø10.9 mm 20X: Ø3.5 or Ø3.8 mm	2.5X: Ø9 or Ø11.0 mm 3X: Ø11.0 mm 5X: Ø10.9 mm 10X: Ø9 or Ø10.9 mm 20X: Ø3.5 mm	2.5X: Ø11 mm 5X, 10X: Ø10.9 mm 20X: Ø3.5 mm	2X, 3X: Ø8 mm 5X, 10X, 15X, 20X: Ø4.5 mm	Ø8.0 mm	Ø10.0 mm	Ø6 mm
Wavefront Error	<λ/4						<λ/10^b
Scratch-Dig	10-5 (20-10 for -E Coating)			20-10			40-20
Optics	Two Best-Form or Spherical Lenses			One Plano-Concave Singlet, One Doublet	Spherical Singlets and Doublets		Two Spherical Mirrors

^aFor Diffraction-Limited Performance
^b Ø1.5 mm Input Beam for BE02R and Ø1 mm Input Beam for BE04R

Left: Typical wire grid plot of the wavefront distortion of a Gaussian beam that has propagated through a BE series Gaussian beam expander. See the table below for the calculated peak-to-valley wavefront distortion value and the RMS wavefront distortion value for each BE series beam expander at its design wavelength.

Thorlabs' BE series of beam expanders are specified to provide diffraction-limited performance, which means that the introduced wavefront distortion in a Gaussian beam will be less than λ/4. However, the nominal performance of the BE series of beam expanders is typically much better than this specification. Below is a table that lists the calculated wavefront distortion for each BE series beam expander and the parameters of the beam used to make the calculation. The beam is normally incident on the beam expander and the propagation direction is such that the output beam is larger than the input beam. Click on the item number in the table to download the corresponding wire grid plot and the data file used to create that plot.

Item#	Input Beam Diameter	Wavelength	Peak-to-Valley Wavefront Distortion	RMS Wavefront Distortion	Output Beam Diameter
BE02M-A	4 mm	543.8 nm	0.0196λ	0.0056λ	8.12 mm
BE02M-B	4 mm	840 nm	0.0113λ	0.0032λ	8.04 mm
BE02M-C	4 mm	1315 nm	0.0100λ	0.0029λ	8.02 mm
BE03M-A	4 mm	543.8 nm	0.0255λ	0.0075λ	11.68 mm
BE03M-B	4 mm	840 nm	0.0117λ	0.0034λ	11.67 mm
BE03M-C	4 mm	1315 nm	0.0050λ	0.0015λ	11.67 mm
BE05M-A	2.25 mm	543.8 nm	0.0068λ	0.0019λ	10.91 mm
BE05M-B	2.25 mm	840 nm	0.0025λ	0.0007λ	10.90 mm
BE05M-C	2.25 mm	1315 nm	0.0009λ	0.0002λ	10.91 mm
BE10M-A	2.25 mm	543.8 nm	0.0185λ	0.0040λ	21.77 mm
BE10M-B	2.25 mm	840 nm	0.0685λ	0.0197λ	21.41 mm
BE10M-C	2.25 mm	1315 nm	0.0547λ	0.0159λ	21.33 mm
BE15M-A	2.25 mm	543.8 nm	0.0163λ	0.0034λ	32.73 mm
BE15M-B	2.25 mm	840 nm	0.0576λ	0.0163λ	32.18 mm
BE15M-C	2.25 mm	1315 nm	0.0430λ	0.0124λ	32.04 mm
BE20M-A	2.25 mm	543.8 nm	0.1022λ	0.0276λ	44.59 mm
BE20M-B	2.25 mm	840 nm	0.0288λ	0.0074λ	43.75 mm
BE20M-C	2.25 mm	1315 nm	0.0309λ	0.0085λ	43.51 mm

Please Give Us Your Feedback

Email		Feedback On
(Optional)
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 1 2 3 4Very Useful

Enter Comments Below:

Characters remaining 8000

Posted Comments:

Poster: bdada

Posted Date: 2012-02-10 19:25:00.0

Response from Buki at Thorlabs to omertzang: Thank you for your feedback on our variable beam expanders. Unfortunately, we don't have any specific data on the damage threshold for femtosecond pulsed light. We expect the beam expander to withstand 100 mJ/cm2 for a 10ns pulse but we cannot use this information to calculate the damage threshold for a femtosecond pulse due to different damage mechanisms.

Poster: doron.azoury

Posted Date: 2012-02-09 05:25:52.0

Can you please provide information regarding the damage threshold for pulsed laser. We use femtosecond 80MHz laser with energy of 10^-6 J/cm^2. Can these beam expanders hold this energy level?

Poster: bdada

Posted Date: 2011-11-04 11:39:00.0

Response from Buki at Thorlabs: Thank you for your interest in our beam expanders. We are considering the addition of a locking screw as a standard feature, but we are able to provide it as a custom for now. We have contacted you regarding the Zemax file. Please contact TechSupport@thorlabs.com if you have further questions.

Poster: james.parker

Posted Date: 2011-11-02 13:36:48.0

Hi, I'm interested in your range of beam expanders, mainly the BE02M for my current requirement. I would like to know the effect of wavelength change on the collimation. If you could please send me the Zemax file for this unit that would be great. A feature that I would like to see on these beam expanders is a locking screw for the adjustment. Best regards, James

Poster: bdada

Posted Date: 2011-11-01 16:40:00.0

Response from Buki at Thorlabs: Thank you for using our Feedback tool. It is possible to use the beam expanders in the reverse direction as a beam reducer. 2x or 3x reduction from 10mm would typically be ok. If the reduction is very large there could be issues with divergence and the damage threshold of the internal optics. We have contacted you to further discuss your application.

Poster: puje

Posted Date: 2011-11-01 06:57:35.0

Hello Thorlabs, can the beam expanders (Be series) be used also as beam reducers (i.e. "the other way around" so to speak) or are there problems associated with this? I have a 10-mm beam diameter that I would like to reduce by a factor of 2 or 3, and also have the option of fine-tuning the divergence of the smaller beam.

Poster: bdada

Posted Date: 2011-09-22 19:33:00.0

Response from Buki at Thorlabs: The input aperture, meaning the input opening, of the BE10M 10X beam expander is Ø4.5mm. On the other hand, we specify the 1/e^2 maximum input beam diameter to be 2.25mm for diffraction limited performance. This means that, as long as the input beam diameter is smaller than 2.25mm, the introduced wavefront distortion in a Gaussian beam will be less than ?/4. However, the nominal performance of the BE series of beam expanders is typically much better than this specification. Now going back to your question, if you use a 3mm beam, the expansion will still be about 10X but the performance would not be better than specified at the recommended beam diameter. Please refer to the "Wavefront Data" tab on the product page to see the values of the calculated beam distortion for our beam expanders at 2.25mm input beam diameter.

Poster: m9903104

Posted Date: 2011-09-22 19:23:08.0

Hi, Im interest in your product: Laser Expander BE10M but I have some questions: the spec says the aperture is 4.5(mm) and max input beam diameter is 2.25(mm) I was wondering if input beam diameter is 3(mm), will output beam diameter be 30(mm) ? Or maximun output beam only 22.5(mm) for 10x expansion?

Poster: jjurado

Posted Date: 2011-02-10 14:09:00.0

Response from Javier at Thorlabs to linzemu: Thank you very much for contacting us with your request. In Gaussian optics, the divergence angle is inversely correlated to the beam waist radius. If we only consider far field divergence (the divergence angle near the laser source is very small), this relationship is given by theta = lambda/(pi * r), where theta is the divergence angle, lambda is the wavelength of the source, and r is the beam waist radius. You can see then, as the radius of the beam waist increases, the divergence angle becomes smaller at the same rate. For example, the specified beam divergence of our HRR005 HeNe laser (0.5 mW, 0.6328 um) is specified as 1.41 mrad. After a 10X expansion, the divergence angle is then equal to (1/10)* 1.41 mrad, or 0.141 mrad.

Poster: tor

Posted Date: 2011-01-05 09:57:24.0

Response from Tor at Thorlabs to David: Thank you for your interest in our beam expanders. I will check to see if we are able to provide your requested files.

Poster: david.m.brown

Posted Date: 2011-01-04 19:46:32.0

BE05M-C, BE10M-C, BE15M-C Would it be possible to acquire the ZEMAX files for one or all of these? I buy a lot of things from thorlabs and it would be simply fantastic if I was able to have these files to make sure the instrument I am planning to build with these is going to work as expected.

Poster: apalmentier

Posted Date: 2009-12-17 18:53:06.0

A response from Adam at Thorlabs: Thank you for the notification, we are going to have our web team correct this as soon as possible. I will also see if we can provide the appropriate Zemax files you are looking for.

Poster: flickingerd

Posted Date: 2009-12-17 17:11:45.0

The links under the "Wavefront Data" tab seem to be broken. Im interested in the available information about part BE02M-B. If a ZEMAX file was available as well, that would be great to have.

Poster: apalmentieri

Posted Date: 2008-08-01 14:25:28.0

We should consider adding Zemax files for customers to download.

Poster: Laurie

Posted Date: 2008-06-27 08:45:50.0

Response from Laurie at Thorlabs to srubin: Thank you for your feedback. The input and output drawings are transposed on the .pdf document. We will fix this ASAP.

Poster: srubin

Posted Date: 2008-06-26 22:54:07.0

I think there is a mistake in the drawing of the BE20M. in the PDF file the output side is described to have a SM1 lens while the input as an SM2 thread.

Poster: technicalmarketing

Posted Date: 2008-01-07 08:40:30.0

Katherine, We do indeed have enough stock of the BE02M-A to complete your request for 2 of these. In addition, the BE02M-A 2X beam expanders #4-40 tap could be drilled larger if you have access to a mill. Alternatively, if you request a larger tap, it is also possible for us to drill the tap for you. The width of the ring on which that tap is drilled is about 5/8" (~7 mm), so there is some room to make the tap larger. Alternatively, I would recommend using one of our screw adapters. Theyre inexpensive and then you would always have the option of going back to the 4-40 tap should your needs change. You can find the adapters at the following link if you are interested: http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=1745&visNavID=836 Specifically, you can change from a 4-40 external thread to 8-32 with part number AP8E4E, and then from 8-82, you can change to an external thread of M4 (Item# AS4M8E), 1/4-20 (Item# AS25E8E), or M6 (Item# AS6M8E) or to an internal thread of 1/4-20 (Item# AI25E8E) or M6 (Item# AI6M8E). If you would like to speak to someone about your specific application, we would invite you to call and speak to one of our applications engineers (973-579-7227). Thank you for your interest in our products, and I hope this information is helpful.

Poster: tung_katherine

Posted Date: 2008-01-05 02:37:42.0

I am interest in your BE02M-A production. But I have one question need to ask. Is it possible to extend #4-40 tapped Hole to 2 or 3 times bigger let us can mount it on our holder? If we want to buy 2 do you have them in stock? Please contact me A.S.A.P. Sincerely Katherine

Click on any phrase below to search our site using our new Search Engine: