Definition of beam expander

Photonics Dictionary

beam expander: A beam expander is an optical device that increases the diameter of a laser beam or other collimated light beam while maintaining its parallelism. This tool is commonly used in laser applications to reduce the beam's divergence, improve focus, or adapt the beam to specific optical systems.

Function: A beam expander increases the diameter of a beam, which typically reduces its divergence (the spread of the beam over distance) and can improve the beam's focusability and collimation.

Design:

Keplerian beam expander: Uses two positive lenses arranged in a telescope configuration. The first lens (objective) collimates the incoming beam, and the second lens (eyepiece) re-collimates it with a larger diameter.

Galilean beam expander: Consists of a positive lens and a negative lens. It is simpler and shorter than the Keplerian design and has the advantage of not inverting the image.

Magnification: The ratio of the output beam diameter to the input beam diameter. For example, a 10x beam expander increases the beam diameter by ten times.

Applications:

Laser systems: Used to reduce beam divergence, enabling the laser to maintain its intensity over longer distances or focus more tightly.

Optical communication: Expands beams in free-space optical communication to cover larger areas or focus on distant targets.

Metrology and inspection: Expands the beam to illuminate a larger area uniformly, which is useful in surface inspection and other precision measurements.

Adaptive optics: In astronomy and other applications, beam expanders are used to match the beam size with the entrance aperture of optical systems or to reduce the effect of diffraction.

Importance: Beam expanders are essential in precision laser systems and optical applications, enabling better control over the beam's characteristics and enhancing the performance of various optical instruments. By modifying the beam's diameter and divergence, beam expanders help optimize the delivery and manipulation of light in scientific, industrial, and communication technologies.

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