Editing Q factor (section)

== Optical systems ==
In [[optics]], the {{mvar|Q}} factor of a [[resonant cavity]] is given by
<math display="block">Q = \frac{2\pi f_o\,E}{P}, \,</math>
where {{mvar|f<sub>o</sub>}} is the resonant frequency, {{mvar|E}} is the stored energy in the cavity, and {{math|1= ''P'' = −{{sfrac|''dE''|''dt''}}}} is the power dissipated. The optical {{mvar|Q}} is equal to the ratio of the resonant frequency to the bandwidth of the cavity resonance. The average lifetime of a resonant [[photon]] in the cavity is proportional to the cavity's {{mvar|Q}}. If the {{mvar|Q}} factor of a [[laser]]'s cavity is abruptly changed from a low value to a high one, the laser will emit a [[Pulse (physics)|pulse]] of light that is much more intense than the laser's normal continuous output. This technique is known as [[Q-switching|{{mvar|Q}}-switching]]. {{mvar|Q}} factor is of particular importance in [[plasmonics]], where loss is linked to the damping of the [[surface plasmon resonance]].<ref>{{Cite journal|last1=Tavakoli|first1=Mehdi|last2=Jalili|first2=Yousef Seyed|last3=Elahi|first3=Seyed Mohammad|date=2019-04-28|title=Rayleigh-Wood anomaly approximation with FDTD simulation of plasmonic gold nanohole array for determination of optimum extraordinary optical transmission characteristics|journal=Superlattices and Microstructures|language=en|volume=130|pages=454–471|doi=10.1016/j.spmi.2019.04.035|bibcode=2019SuMi..130..454T|s2cid=150365680}}</ref> While loss is normally considered a hindrance in the development of plasmonic devices, it is possible to leverage this property to present new enhanced functionalities.<ref>{{Cite journal|last1=Chen|first1=Gang|last2=Mahan|first2=Gerald|last3=Meroueh|first3=Laureen|last4=Huang|first4=Yi|last5=Tsurimaki|first5=Yoichiro|last6=Tong|first6=Jonathan K.|last7=Ni|first7=George|last8=Zeng|first8=Lingping|last9=Cooper|first9=Thomas Alan|date=2017-12-31|title=Losses in plasmonics: from mitigating energy dissipation to embracing loss-enabled functionalities|journal=[[Advances in Optics and Photonics]]|language=EN|volume=9|issue=4|pages=775–827|doi=10.1364/AOP.9.000775|bibcode=2017AdOP....9..775B|issn=1943-8206|doi-access=free|arxiv=1802.01469}}</ref>