Editing Optical cavity (section)

==Resonator modes==
[[Image:Optical-cavity-en.svg|thumb|Types of two-mirror optical cavities, with mirrors of various curvatures, showing the radiation pattern inside each cavity.]]

Light confined in a resonator will reflect multiple times from the mirrors, and due to the effects of [[Interference (wave propagation)|interference]], only certain patterns and [[frequency|frequencies]] of radiation will be sustained by the resonator, with the others being suppressed by destructive interference. In general, radiation patterns which are reproduced on every round-trip of the light through the resonator are the most stable. These are known as the ''modes'' of the resonator.<ref>{{cite journal |first=H.K.V. |last=Lotsch |title=The scalar theory for optical resonators and beam waveguides. |journal=Optik |volume=26 |year=1967 |pages=112–130}}</ref>

Resonator modes can be divided into two types: [[longitudinal mode]]s, which differ in frequency from each other; and [[transverse mode]]s, which may differ in both frequency and the [[Intensity (physics)|intensity]] pattern of the light. The basic, or fundamental transverse mode of a resonator is a [[Gaussian beam]].