# Coupling parameter

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Coupling_parameter
> Markdown URL: https://mediated.wiki/source/Coupling_parameter.md
> Source: https://en.wikipedia.org/wiki/Coupling_parameter
> Source revision: 1291896781
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

{{More citations needed|date=November 2022}}

The '''coupling parameter''' of the resonator specifies the part of the energy of the laser field, which is output at each round-trip.<ref>{{Citation |last=Nishiyama |first=H. |title=Dynamics of low coupling parameter free-electron laser oscillator |date=2003-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780444514172500249 |work=Free Electron Lasers 2002 |pages=74–78 |editor-last=Kim |editor-first=K. -J. |place=Amsterdam |publisher=Elsevier |language=en |doi=10.1016/b978-0-444-51417-2.50024-9 |isbn=978-0-444-51417-2 |access-date=2022-11-25 |last2=Asakawa |first2=M. |last3=Tsunawaki |first3=Y. |last4=Heya |first4=M. |last5=Awazu |first5=K. |last6=Imasaki |first6=K. |editor2-last=Milton |editor2-first=S. V. |editor3-last=Gluskin |editor3-first=E.|url-access=subscription }}</ref> The coupling parameter should not be confused with the [round-trip loss](/source/round-trip_loss), which refers to the part of the energy which is absorbed or scattered at each round-trip of laser field in the [laser resonator](/source/laser_resonator), and cannot be used.

At the continuous wave operation, the [round-trip gain](/source/round-trip_gain) is determined by the coupling parameter and the round-trip loss. In simple configurations of the [laser cavity](/source/laser_cavity) or [laser resonator](/source/laser_resonator), the coupling parameter may be just the transmission coefficient of the output coupler or just square of the [magnification coefficient](/source/magnification_coefficient) in the case of an [unstable resonator](/source/unstable_resonator).

The round-trip loss may limit the power scaling of the [active mirror](/source/active_mirror)s, or [disk laser](/source/disk_laser)s, while the size of the [gain medium](/source/gain_medium) scales up, and the gain size product is limited by the exponential growth of the [amplified spontaneous emission](/source/amplified_spontaneous_emission); the powerful [disk laser](/source/disk_laser) should work at low values of the coupling parameter and even lower values of the round-trip loss.

==See also==
*[Disk laser](/source/Disk_laser)

{{DEFAULTSORT:Coupling Parameter}}

== References ==
{{Reflist}}{{Optics-stub}}

Category:Laser science

---
Adapted from the Wikipedia article [Coupling parameter](https://en.wikipedia.org/wiki/Coupling_parameter) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Coupling_parameter?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.