In
optics, a
Gaussian beam is a
beam of monochromatic
electromagnetic radiation whose transverse magnetic and
electric field amplitude profiles are given by the
Gaussian function; this also implies a Gaussian
intensity (irradiance) profile. This fundamental (or TEM
00)
transverse gaussian mode describes the intended output of most (but not all) lasers, as such a beam can be focused into the most concentrated spot. When such a beam is refocused by a
lens, the transverse
phase dependence is altered; this results in a
different Gaussian beam. The electric and magnetic field amplitude profiles along any such circular Gaussian beam (for a given
wavelength and
polarization) are determined by a single parameter: the so-called waist
w0. At any position
z relative to the waist (focus) along a beam having a specified
w0, the field amplitudes and phases are thereby determined as detailed below.