Features

• Use to Enlarge or Reduce the Diameter of a Collimated Beam of Light
• Superb Chromatic Compensation Due to Use of Spherical Mirrors
• Mirrors are Stationary Leading to Fixed Focus
• Offer High Transmission from 450 nm to 20 μm
• Max 1/e² Input (Expansion) Beam Diameter: 3 mm

Thorlabs' Reflective Beam Expanders are mirror-based beam expanders, offering either 2X or 4X expansion or reduction. Due to dispersion, lens-based beam expanders are only capable of compensating for focus at one wavelength of light, making them only suitable for expanding/reducing monochromatic sources. Reflective beam expanders, on the other hand, use mirrors, which have constant focal lengths, regardless of the light being focused. Thus, reflective beam expanders can be used with collimated polychromatic light without the need of any fine focus adjustment.

Our reflective beam expanders use two protected silver-coated spherical mirrors, offering high reflectance over a broad spectral range (R > 96% from 450 nm to 2.0 µm). The BE02R housing is 16 mm cage system compatible at the entrance and exit ports, while also internally SM05 threaded. The BE04R has a 16 mm cage system compatible entrance port and a 30 mm cage system compatible exit port, providing internal SM05 and SM1 threading, respectively. The SM series threading allows for our lens tubes and mounted filters to be attached to the housing, while the cage system compatibility provides a simple way to build complex setups. One particularly useful application of a reflective beam expander is to use one to reduce the diameter of a polychromatic beam and then couple the light into multimode fiber using a parabolic mirror collimator.

The Reflective Beam Expanders can be mounted to an optical table or breadboard using two CL6 Table Clamps (two CL2 or CL3 clamps will also work). Two post mounting options are also available: use two RM1C Pillar Post Angle Clamps or an RM1D Adjustable Height C-Clamp to secure the beam expander to a Ø1" Pedestal Pillar Post.

Thorlabs also offers many other types of beam expanders, including Galilean beam expanders with variable or fixed zoom ratios. Both sliding and rotating adjustment mechanisms are avaialbe. For more information on our extensive line of beam expanders, please click on the Selection Guide tab.

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Excel Spreadsheet with Raw Data for Protected Silver, 8° AOI

This graph is for unpolarized light. The shaded region denotes the range over which we recommend using these beam expanders.

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.