The divergence of good-quality laser beams is modeled using the mathematics of Gaussian beams. Gaussian laser beams are said to be diffraction limited when their radial beam divergence is close to the minimum possible value, which is given by where is the laser wavelength and is the radius of the beam at its narrowest point, which is called the "beam waist". This type of beam divergence is observed from optimized laser cavities. Information on the diffraction-limited divergence of a coherent beam is inherently given by the N-slit interferometric equation. See also Laser beam profiler Laser linewidth References External links Laser divergence calculator Interactive beam divergence graph Optics Antennas (radio)