• 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

This Reflective Beam expander is a mirror-based beam expander, offering 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 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.

This Reflective Beam Expander can be mounted to an optical table or breadboard using either two CL6 Table Clamps (two CL1, 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.

• Magnification: 4X
• RMS Wavefront Error: ?/10
• Average Reflectance (450 nm - 2 µm): >97.5%
• Average Reflectance (2 - 20 µm): >96%
• Mirror Substrate: N-BK7/BK7
• Clear Input Aperture: 6 mm
• Scratch-Dig: 40-20