# Gaussian beam (beam width at a distance equal to the Rayleigh range)

## Description

In optics, a Gaussian beam is a beam of electromagnetic radiation whose transverse electric field and intensity (irradiance) distributions are well approximated by Gaussian functions. Many lasers emit beams that approximate a Gaussian profile. For a Gaussian beam propagating in free space, the spot size (radius) will be at a minimum value at one place along the beam axis, known as the beam waist. The Rayleigh range is the distance along the propagation direction of a beam from the waist to the place where the area of the cross section is doubled. At a distance from the waist equal to the Rayleigh range , the width of the beam is related to the waist size.

Related formulas## Variables

w_{zR} | Beam width at a distance equal to the Rayleigh range (m) |

w_{0} | The waist size (m) |