Gaussian beam: a standalone construct

A Gaussian beam is the idealised beam of coherent light whose intensity across any cross-section follows a bell-shaped Gaussian profile, narrowing to a minimum radius called the waist and then spreading as it propagates, with its curvature and width evolving in a way fixed entirely by the waist size and wavelength. Kogelnik and Li's 1966 Laser beams and resonators set out this description as the fundamental transverse mode of a laser resonator, including the waist, the Rayleigh range over which the beam stays roughly collimated, and the far-field divergence. The referent is the spatial structure of a diffraction-limited laser beam, the baseline for focusing, coupling, and resonator design throughout photonics.[1]

Unit

The beam-waist radius and Rayleigh range that fix the beam's width and divergence

Recovery means

Not applicable

Measured by

Characterised by the waist radius, the Rayleigh range, the far-field divergence, and the beam-quality factor against the ideal