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For a single mode TEM 00 (Gaussian) laser beam, M 2 is exactly one. Unlike the beam parameter product, M 2 is unitless and does not vary with wavelength. The M 2 value for a laser beam is widely used in the laser industry as a specification, and its method of measurement is regulated as an ISO standard. [2]
The M (mode) factor was introduced to experimentally measure the presence of higher-order modes within a Gaussian-like beam. In early 1970, Larry Marshall [ 2 ] noted, 'Despite variations of intensity cross sections from gaussian shape, it is still convenient to define beam diameter as M times the 1/e^2 diameter of the equivalent gaussian mode'.
The Gaussian function has a 1/e 2 diameter (2w as used in the text) about 1.7 times the FWHM.. At a position z along the beam (measured from the focus), the spot size parameter w is given by a hyperbolic relation: [1] = + (), where [1] = is called the Rayleigh range as further discussed below, and is the refractive index of the medium.
MFM images of 3.2 Gb and 30 Gb computer hard-drive surfaces. Comparison of Faraday-effect image (left) and MFM image (inset, lower-right) of a magnetic film. Magnetic force microscopy (MFM) is a variety of atomic force microscopy, in which a sharp magnetized tip scans a magnetic sample; the tip-sample magnetic interactions are detected and used to reconstruct the magnetic structure of the ...
[6] [7] The D4σ beam width is the ISO standard definition and the measurement of the M 2 beam quality parameter requires the measurement of the D4σ widths. [6] [7] [8] The other definitions provide complementary information to the D4σ. The D4σ and knife-edge widths are sensitive to the baseline value, whereas the 1/e 2 and FWHM widths are ...
A unit of measurement, or unit of measure, is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. [1] Any other quantity of that kind can be expressed as a multiple of the unit of measurement. [2] For example, a length is a physical quantity.
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The equipment used for communications over multi-mode optical fiber is less expensive than that for single-mode optical fiber. [1] Typical transmission speed and distance limits are 100 Mbit/s for distances up to 2 km (), 1 Gbit/s up to 1000 m, and 10 Gbit/s up to 550 m.