Editorial Feature

What is a Beamsplitter?

Beamsplitters are elements that redirect a portion of the incident beam of light and allow the rest of the light to continue in the original direction. Beamsplitter elements may be simple or complex systems. A simple beam splitter consists of a square or rectangular glass sheet that is coated with a reflective material, while a complex system can be an integrated multi-element optical assembly.

A beamsplitter partially transmits light and partially reflects the incident light in unequal proportions. Apart from splitting the incident light, beamsplitters can be used to recombine two separate light beams or images into a single line. Plate, cube and perforated are the commonly available types of beam splitters.

Schematic of a beamsplitter as part of a Michelson Interferometer. Image Credit: Florida International University

Working Principle

A simple beamsplitter consists of two right-angled prisms, coated on the hypotenuse with a semi-reflective coating, cemented together to form a cube. When light is incident on this cube a portion of light is reflected at 90o at the mirrored interface, while the rest of the light passes through the prism in the same direction.


Some of the applications of beam splitters are as below:

  • Scientific instruments – interferometers, spectrometers and fluorimeters
  • Optical instruments – microscopes, binoculars, range finders, and survey equipment

Sources and Further Reading


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