![]() The linewidth (FWHM) is proportional to the square of the resonator bandwidth divided by the output power (assuming that there are no parasitic resonator losses). (This is particularly the case for lasers with dominating low-frequency phase noise.) More data are required for full noise specifications.Ī simple way to define the linewidth would be to use the root-mean-square (r.m.s.) value of the instantaneous optical frequency: This shows that the linewidth alone, or even the linewidth complemented with a spectral shape (line shape), does by far not provide full information on the spectral purity of laser light. (Phase fluctuations which are restricted to a small interval of phase values lead to a zero linewidth and some noise sidebands.) Drifts of the resonator length can further contribute to the linewidth and can make it dependent on the measurement time. A finite linewidth arises from phase noise if the optical phase undergoes unbounded drifts, as is the case for free-running laser oscillators, for example. The linewidth of a light beam is strongly (but non-trivially) related to the temporal coherence, characterized by the coherence time or coherence length. from gas discharge lamps have certain linewidths, which can depend on the operation conditions. More precisely, it is the width of the power spectral density of the emitted electric field in terms of frequency, wavenumber or wavelength. a single-frequency laser, is the width (typically the full width at half-maximum, FWHM) of its optical spectrum. The linewidth (or line width) of a laser, e.g. How to cite the article suggest additional literature More specific terms: emission linewidth, laser linewidth, Schawlow–Townes linewidthĬategories: laser devices and laser physics, fluctuations and noise, physical foundations Definition: width of the spectrum of a light beam or an absorption feature
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