In the term mode coupling, as used in physics and electrical engineering, the word "mode" refers to

eigenmode In linear algebra, an eigenvector () or characteristic vector of a linear transformation is a nonzero vector that changes at most by a scalar factor when that linear transformation is applied to it. The corresponding eigenvalue, often denoted ...

s of an idealized, "unperturbed",

linear system In systems theory, a linear system is a mathematical model of a system based on the use of a linear operator. Linear systems typically exhibit features and properties that are much simpler than the nonlinear case. As a mathematical abstraction o ...

. The

superposition principle The superposition principle, also known as superposition property, states that, for all linear systems, the net response caused by two or more stimuli is the sum of the responses that would have been caused by each stimulus individually. So tha ...

says that eigenmodes of linear systems are independent of each other: it is possible to excite or to annihilate a specific mode without influencing any other mode; there is no

dissipation In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. In a dissipative process, energy (internal, bulk flow kinetic, or system potential) transforms from an initial form to a ...

. In most real systems, however, there is at least ''some''

perturbation Perturbation or perturb may refer to: * Perturbation theory, mathematical methods that give approximate solutions to problems that cannot be solved exactly * Perturbation (geology), changes in the nature of alluvial deposits over time * Perturbat ...

that causes energy transfer between different modes. This perturbation, interpreted as an interaction between the modes, is what is called "mode coupling". Important applications are: * In

fiber optics An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...

{{cite journal , last1=Thomas , first1=Jens , last2=Jovanovic , first2=Nemanja , last3=Becker , first3=Ria G. , last4=Marshall , first4=Graham D. , last5=Withford , first5=Michael J. , last6=Tünnermann , first6=Andreas , last7=Nolte , first7=Stefan , last8=Steel , first8=M. J. , title=Cladding mode coupling in highly localized fiber Bragg gratings: modal properties and transmission spectra , journal=Optics Express , publisher=The Optical Society , volume=19 , issue=1 , date=22 December 2010 , pages=325–341 , issn=1094-4087 , doi=10.1364/oe.19.000325 , pmid=21263572 , doi-access=free * In

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...

s (compare

mode-locking Mode locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s). A laser operated in this way is sometimes r ...

) * In

condensed-matter physics Condensed matter physics is the field of physics that deals with the macroscopic and microscopic physical properties of matter, especially the solid and liquid State of matter, phases which arise from electromagnetic forces between atoms. More ge ...

critical slowing down Critical or Critically may refer to: *Critical, or critical but stable, medical states **Critical, or intensive care medicine *Critical juncture, a discontinuous change studied in the social sciences. *Critical Software, a company specializing in ...

can be described by a

Coupled mode theory Coupled mode theory (CMT) is a perturbational approach for analyzing the coupling of vibrational systems (mechanical, optical, electrical, etc.) in space or in time. Coupled mode theory allows a wide range of devices and systems to be modeled as on ...

.See e.g. W. Götze, ''Complex Dynamics of glass forming liquids. A mode-coupling theory'', Oxford: Oxford University Press (2009).

References

Condensed matter physics Nonlinear optics Fiber-optic communications

See also

References