Features

• 2.5X, 5X, 10X, or 20X Beam Expansion
• Produce Diverging, Collimated, or Focusing Beams
• Sliding Lens Adjustment that Minimizes Walk-Off
• Best Form Narrowband AR-Coated Lenses
• High Damage Threshold of 2 GW/cm²
• Removable Endcaps Protect Optics

The ELQ 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 that are designed to minimize aberrations in the recollimated beam. Both optics have narrowband 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 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 a narrowband AR coating for 248 nm or 351 nm or a broadband AR coating for the 400 - 650 nm, 650 - 1050 nm, or 1050 - 1620 nm range. 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
ELQ-25-2.5X-1064		X
ELQ-25-5X-1064	X
ELQ-25-10X-1064	X
ELQ-25-20X-1064		X

^a Average Reflectance over AR Coating Range
^b Transmittance

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.