Editorial Feature

What is a Beam Combiner?

A beam combiner is essentially an arrangement of beam splitters and mirrors. The function of a beam splitter is to divide the incident light into two paths, one by transmission and another by reflection. Beam splitters are coated with a material that enables the glass to reflect monochromatic light and transmit light of other wavelengths.

In order to have minimum dispersion of light, a beam combiner is constructed using a combination of three beam splitters. The coating used in the beam splitter is of great importance in reducing the dispersion and retardance of the incident light beam. Beam combiners are used in varied applications, from combining laser beams, to combining light from stars in astronomy.

Working Principle

A beam combiner works on the same principle as a beam splitter, where a portion of the incident beam is reflected at 90°, while the rest of it is transmitted in the same direction.


A beam combiner may be a combination of beam splitters and mirrors, or simply several beam splitters.


Some of the applications of beam combiners are listed below:

  • Astronomical observations/measurements
  • Laser light combination
  • Nulling interferometry

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