Search results
Results From The WOW.Com Content Network
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 [2] =, where is the laser wavelength and is the radius of the beam at its narrowest point, which is ...
The beam divergence of a laser beam is a measure for how fast the beam expands far from the beam waist. It is usually defined as the derivative of the beam radius with respect to the axial position in the far field, i.e., in a distance from the beam waist which is much larger than the Rayleigh length. This definition yields a divergence half-angle.
For a Gaussian beam, the BPP is the product of the beam's divergence and waist size w 0. The BPP of a real beam is obtained by measuring the beam's minimum diameter and far-field divergence, and taking their product. The ratio of the BPP of the real beam to that of an ideal Gaussian beam at the same wavelength is known as M 2 ("M squared").
The beam of a single transverse mode (gaussian beam) laser eventually diverges at an angle that varies inversely with the beam diameter, as required by diffraction theory. Thus, the "pencil beam" directly generated by a common helium–neon laser would spread out to a size of perhaps 500 kilometers when shone on the Moon (from the distance of ...
For example, a laser sight is a small, usually visible-light laser placed on a handgun or a rifle and aligned to emit a beam parallel to the barrel. Since a laser beam has low divergence, the laser light appears as a small spot even at long distances; the user places the spot on the desired target and the barrel of the gun is aligned (but not ...
In laser science, the parameter M 2, also known as the beam propagation ratio or beam quality factor is a measure of laser beam quality. It represents the degree of variation of a beam from an ideal Gaussian beam. [1] It is calculated from the ratio of the beam parameter product (BPP) of the beam to that of a Gaussian beam with the same wavelength.
Beams with power well out in the "tails" of the distribution have M 2 much larger than one would expect. In theory, an idealized tophat laser beam has infinite M 2, although this is not true of any physically realizable tophat beam. For a pure Bessel beam, one cannot even compute M 2. [5] The definition of "quality" also depends on the application.
In laser science, the beam parameter product (BPP) is the product of a laser beam's divergence angle (half-angle) and the radius of the beam at its narrowest point (the beam waist). [1] The BPP quantifies the quality of a laser beam, and how well it can be focused to a small spot.