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Spectral coherence, Part I: Passive-resonator linewidth, fundamental laser linewidth, and Schawlow-Townes approximation

Pollnau, M.; Eichhorn, Marc 1
1 Institut für Regelungs- und Steuerungssysteme (IRS), Karlsruher Institut für Technologie (KIT)


The degree of spectral coherence characterizes the spectral purity of light. It can be equivalently expressed in the time domain by the decay time τ or the quality factor Q of the light-emitting oscillator, the coherence time τ $^{coh}$ or length l$^{coh}$ of emitted light or, via Fourier transformation to the frequency domain, the linewidth Δν of emitted light. We quantify these parameters for the reference situation of a passive Fabry-Pérot resonator. We investigate its spectral line shapes, mode profiles, and Airy distributions and verify that the sum of all mode profiles generates the corresponding Airy distribution. The Fabry-Pérot resonator is described, as an oscillator, by its Lorentzian linewidth and finesse and, as a scanning spectrometer, by its Airy linewidth and finesse. Furthermore, stimulated and spontaneous emission are analyzed semi-classically by employing Maxwell′s equations and the law of energy conservation. Investigation of emission by atoms inside a Fabry-Pérot resonator, the Lorentz oscillator model, the Kramers-Kronig relations, the amplitude-phase diagram, and the summation of quantized electric fields consistently suggests that stimulated and spontaneous emission of light occur with a phase 90° in lead of the incident field. ... mehr

Verlagsausgabe §
DOI: 10.5445/IR/1000122140
Veröffentlicht am 11.08.2020
DOI: 10.1016/j.pquantelec.2020.100255
Zitationen: 26
Web of Science
Zitationen: 24
Zitationen: 27
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Regelungs- und Steuerungssysteme (IRS)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 08.2020
Sprache Englisch
Identifikator ISSN: 0079-6727, 1873-1627
KITopen-ID: 1000122140
Erschienen in Progress in quantum electronics
Verlag Elsevier
Band 72
Seiten Art.-Nr.: 100255
Schlagwörter Spectral coherence; Optical resonance; Fabry-Pérot resonator; Resonator linewidth; Finesse; Lasers; Laser theory; Laser resonators; Laser linewidth; Schawlow-Townes equation
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