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In physics, coherence length is the propagation distance over which a coherent wave (e.g. an electromagnetic wave) maintains a specified degree of coherence. Wave interference is strong when the paths taken by all of the interfering waves differ by less than the coherence length. A wave with a longer coherence length is closer to a perfect ...
The coherence length is defined as the distance the wave travels in time . [11]: 560, 571–573 The coherence time is not the time duration of the signal; the coherence length differs from the coherence area (see below).
The coherence time, usually designated τ, is calculated by dividing the coherence length by the phase velocity of light in a medium; approximately given by = where λ is the central wavelength of the source, Δν and Δλ is the spectral width of the source in units of frequency and wavelength respectively, and c is the speed of light in vacuum.
The second order coherence for stellar light as measured in the Hanbury Brown and Twiss experiment as a function of the time delay introduced between the signals /, where is the coherence length. g ( 2 ) ( τ ) = 1 + e − π 2 ( τ τ 0 ) 2 {\displaystyle g^{(2)}(\tau )=1+e^{-{\frac {\pi }{2}}({\frac {\tau }{\tau _{0}}})^{2}}} .
In physics, coherence theory is the study of optical effects arising from partially coherent light and radio sources. Partially coherent sources are sources where the coherence time or coherence length are limited by bandwidth, by thermal noise, or by other effect. Many aspects of modern coherence theory are studied in quantum optics.
The coherence length determines the width of the correlogram, which relies on the spectral width of the light source, as well as on structural aspects such as the spatial coherence of the light source and the numerical aperture (NA) of the optical system. The following discussion assumes that the dominant contribution to the coherence length is ...
Coherence length [ edit ] Within this model the degree of correlation between a pair of planes decreases as the distance between these planes increases, i.e., a pair of planes 10 planes apart have positions that are more weakly correlated than a pair of planes that are nearest neighbours.
He also introduced the notion of coherence length in ... Pippard was the author of Elements of Classical Thermodynamics for Advanced Students of Physics, [14 ...