Rayleigh length (range)
In optics and especially laser science, the Rayleigh length or 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.
Rayleigh length is particularly important when beams are modeled as Gaussian beams. For a Gaussian beam propagating in free space along the z-axis, the Rayleigh length is depended on the wavelength and the radial size of the beam at its narrowest point.
|zR||Rayleigh length (m)|
|w0||The beam waist (m)|
|λ||The wavelength (m)|