ABSTRACT
The Gaussian beam is the simplest case of laser beams actually appearing in practical optical systems. There also exist some other derived parameters, such as the Rayleigh range, which explains the extension of the beam waist along the propagation axis, and the Gouy phase shift, which describes how the phase includes an extra p-phase shift after crossing the beam waist region. Although simple, Gaussian beams exhibit a great variety of realizations when three-dimensional beams are studied. To properly evaluate such effects, certain other parameters have been defined by accounting for the ellipticity of the irradiance pattern, the longitudinal astigmatism, and the twisting of the irradiance profile. Gaussian laser beams are a reference of quality for a laser source. The description of other types of generalized, non-Gaussian, nonspherical, and nonorthogonal, laser beams is referred to the same type of parameters describing the Gaussian case.
