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Journal of the Optical Society of America B

Theory of fluorescence spectra induced by short laser pulses

Maciej Lewenstein, Jakub Zakrzewski, Kazimierz Rza̧żewski

Published Jan 1, 1986• 61 citations
Publisher

Abstract

We consider a single-photon bound–bound and bound–free transitions induced by short, coherent laser pulses. Fluorescence energy spectra are calculated. In the case of the fluorescence to a side level, a number of analytic results are presented. For the resonance-fluorescence case the compact Bloch-like equations are derived for the ionization to an autoionization resonance and numerically analyzed. The multipeak structure of the spectra previously found in the simplified models is shown to be a universal feature. The number of maxima of the spectrum increases with the area of the pulse.

DOI
10.1364/josab.3.000022

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Laser excitation of a two-level atom is analytically studied for arbitrary pulse shape, area, and energy. The ionization mechanism is modeled as a homogeneous width $\ensuremath{\gamma}$ of the atomic excited state. A transformation of the optical Bloch equations allows the dynamics to be completely described by a single equation for the area of the pulse at time ttt, $\ensuremath{\Phi}(t)$. Analytic solutions for the total bound population for a wide variety of pulse shapes can be found in two regions: $\ensuremath{\Phi}(t)\ensuremath{\approx}sin\ensuremath{\Phi}(t)$ and $\ensuremath{\Omega}(t)>\ensuremath{\gamma}$, where $\ensuremath{\Omega}(t)$ is the resonance Rabi frequency. The generalization of the two-level atom results to the NNN-level atom is discussed.
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A quantum electrodynamic treatment of an autoionizing atom excited by a laser field is presented. As the main result, the authors present the average number of photons emitted into a particular mode of the electromagnetic field. In the case of a symmetric autoionizing resonance, the spectrum presented here resembles the power spectrum in resonance fluorescence of a two-level atom. For an asymmetric resonance, however, this spectrum manifests the confluence of coherences. The total number of scattered photons has a maximum at the confluence intensity. The spectrum is asymmetric in this case.