Mechanical Housing Update
Please note that Thorlabs is in the process of updating the mechanical housings of these beam expanders. For more details, see the Mechanical Housing Update section below.

Features

2.5X, 3X, 5X, 10X, or 20X Beam Expansion
Produce Diverging, Collimated, or Focusing Beams
Sliding Lens Adjustment that Minimizes Walk-Off
Best Form or Spherical Broadband AR-Coated Lenses
Four Coating Ranges Available
Damage Threshold: 100 W/cm² (50 W/cm² for -E)
Removable Endcaps Protect Optics

The EL series of Galilean Beam Expanders are designed to expand or reduce the diameter of a collimated beam while introducing a wavefront error of less than λ/4, (i.e., diffraction-limited performance). An expanded beam can be focused to a narrower diffraction-limited waist; such a reduced beam is sometimes necessary for use with optics or instruments that have narrow input apertures such as the SA200 family of scanning Fabry-Perot interferometers.

The housing contains two best form lenses (spherical lenses for -E) that are designed to minimize aberrations in the recollimated beam. Both optics have broadband AR coatings to minimize surface reflections. The input lens is mounted in a precision-milled tube that can slide in and out of the tube containing the output lens. The sliding design allows for the adjustment of the collimating lens and minimizes the beam walk-off effect that is inherent to lens adjustments. The beam expander can be mounted via either the 1/4"-20 or the M6-threaded hole in the base. In addition, the groove milled into the base can be used to clamp the beam expander to an optical table using CL6 mounting cleats (not included). The beam expanders have threaded input and output apertures, which allow additional lenses and filters to be installed easily along the optical axis of the beam expander.

Thorlabs also offers many other types of beam expanders, including lens based variable and fixed beam expanders whose expansion ratio is achieved via rotation as well as beam expanders with a non-rotating adjustment mechanism that have narrowband AR coatings centered at 248 nm, 351 nm, or 1064 nm. Thorlabs also offers reflective beam expanders. For more information on our extensive line of beam expanders, please click on the Selection Guide tab.

Mechanical Housing Update
These beam expanders originally featured an internal C-Mount threading on the input side and an internal M32 x 0.75 threading on the output side. In order to improve mechanical compatibility with Thorlabs' SM05- (0.535"-40) and SM1-threaded (1.035"-40) optomechanics, Thorlabs is in the process of converting the housing design so that it has internal SM05 threading on the input side and internal SM1 threading on the output side. Please refer to the table below to determine whether a given beam expander is currently being shipped with the new housing.

Thorlabs offers an extensive line of thread adapters for converting from one threading to another. Should you have any concerns, please contact Technical Support.

Info	New	Old
Mechanical Drawing (Click for Details)
Input Threading	SM05 (0.535"-40)	C-Mount
Output Threading	SM1 (1.035"-40)	M32 x 0.75
EL-25-2.5X-A		X
EL-25-5X-A	X
EL-25-10X-A	X
EL-25-20X-A		X
EL-25-2.5X-B	X
EL-25-5X-B	X
EL-25-10X-B	X
EL-25-20X-B		X
EL-25-2.5X-C		X
EL-25-5X-C	X
EL-25-20X-C		X
EL-25-3X-E	X
EL-25-5X-E	X

Lens Substrates (-A, -B, and -C Coatings): Fused Silica Lithosil and/or N-SF8
Lens Substrate (-E Coating): CaF₂

Item #	R_avg^a	T^b	Damage Threshold (CW)	Mag.	Max Input Beam Diameter^c (1/e²)	Input Aperture	AR Coating Range	Scratch-Dig	Housing Dimensions
EL-25-2.5X-A	<0.5%	>96%	100 W/cm²	2.5X	4.4 mm	Ø9 mm	400 - 650 nm	10-5	Ø38 x 126 mm
EL-25-2.5X-B	<0.5%	>96%	100 W/cm²	2.5X	4.4 mm	Ø11.0 mm	650 - 1050 nm	10-5	Ø37.9 x 115.0 mm
EL-25-2.5X-C	<0.5%	>96%	100 W/cm²	2.5X	4.4 mm	Ø9 mm	1050 - 1620 nm	10-5	Ø38 x 126 mm
EL-25-3X-E	<2%	>90%	50 W/cm²	3X	4.0 mm	Ø11.0 mm	3000 - 5000 nm	20-10	Ø37.9 x 115.0 mm
EL-25-5X-A	<0.5%	>96%	100 W/cm²	5X	2.2 mm	Ø10.9 mm	400 - 650 nm	10-5	Ø37.9 x 135.0 mm
EL-25-5X-B	<0.5%	>96%	100 W/cm²	5X	2.2 mm	Ø10.9 mm	650 - 1050 nm	10-5
EL-25-5X-C	<0.5%	>96%	100 W/cm²	5X	2.2 mm	Ø10.9 mm	1050 - 1620 nm	10-5
EL-25-5X-E	<2%	>90%	50 W/cm²	5X	2.2 mm	Ø11.0 mm	3000 - 5000 nm	20-10	Ø37.9 x 115.0 mm
EL-25-10X-A	<0.5%	>96%	100 W/cm²	10X	1.1 mm	Ø10.9 mm	400 - 650 nm	10-5	Ø38.0 x 202.1 mm
EL-25-10X-B	<0.5%	>96%	100 W/cm²	10X	1.1 mm	Ø10.9 mm	650 - 1050 nm	10-5	Ø38.0 x 202.1 mm
EL-25-20X-A	<0.5%	>96%	100 W/cm²	20X	0.6 mm	Ø3.5 mm	400 - 650 nm	10-5	Ø38 x 279 mm
EL-25-20X-B	<0.5%	>96%	100 W/cm²	20X	0.6 mm	Ø3.5 mm	650 - 1050 nm	10-5
EL-25-20X-C	<0.5%	>96%	100 W/cm²	20X	0.6 mm	Ø3.5 mm	1050 - 1620 nm	10-5

Average Reflectance over AR Coating Range
Transmission
For Diffraction-Limited Performance

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

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Posted Comments:

Poster:

Posted Date: 2009-05-05 03:31:57.0

By using an adapter, SM2B2 (http://www.thorlabs.com/thorProduct.cfm?partNumber=SM2B2), that slides over the body of the beam expander, you can then thread it into a cage plate with SM2 threads. This way you can attach the beam expander very close to its center of gravity or even right on it if you remove the mounting saddle.

Poster:

Posted Date: 2009-05-05 03:31:30.0

Poster: techsupport

Posted Date: 2009-05-04 17:33:00.0

A response from Erin at Thorlabs to Wei: In order to mount the beam expander into a cage system you can use a system similar to the SM1A9 thread adapter, which will go from C-Mount (which is accessible once the end cap is removed from the input side of the expander) to our SM1 thread. From this adapter you could use the SM1T2 to connect to the LCP02. This will allow you to directly connect to the 60mm cage system over the expander and to the 30mm cage system before the input to the expander, if this is the system you are currently using. Unfortunately, due to the weight of the beam expander, this would not be able to completely support the weight, so we recommend using a post on the bottom of the expander to support it. Please note that it does have ¼-20 and M6 threaded holes on the bottom, so you could mount it to a pillar post. For more details on this, please let me know the total height of your cage system and any other details you have about it and I can help you find the correct solution. Please also let me know if you have any further questions on our products and I will be happy to help you. Have a nice day. SM1A9 C-Mount to SM1 Adapter: http://www.thorlabs.com/thorProduct.cfm?partNumber=SM1A9 LCP02 Cage Plate Adapter: http://www.thorlabs.com/thorProduct.cfm?partNumber=LCP02 SM1T2 Thread Nut: http://www.thorlabs.com/thorProduct.cfm?partNumber=SM1T2 Drawing of EL-25-5X-A: http://www.thorlabs.com/Thorcat/17400/17485-E0W.pdf

Poster: zhaow2

Posted Date: 2009-05-04 12:36:53.0

Is there a way I put EL-25-5X-A into the cage system? thanks, Wei

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