Collective Atomic Dynamics in Resonance Fluorescence
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ND LASER PHYSICS
Collective Atomic Dynamics in Resonance Fluorescence A. I. Trubilkoa, * and A. M. Basharovb, c, ** a
St. Petersburg University of State Fire Service of Emercom of Russia, St. Petersburg, 196105 Russia b National Research Center Kurchatov Institute, Moscow, 123182 Russia c Moscow Institute of Physics and Technology (National Research University), Dolgoprudnyi, Moscow region, 141701 Russia *e-mail: [email protected] **e-mail: [email protected] Received May 4, 2020; revised May 4, 2020; accepted May 7, 2020
A new collective effect has been revealed in resonance fluorescence: the side and central components of the triplet in the emission spectrum of an atomic ensemble excited by an intense coherent field are narrowed in the case of the critical number of atoms in the ensemble. DOI: 10.1134/S0021364020120139
1. INTRODUCTION The resonance fluorescence of a single atom and an atomic ensemble is a fundamental nonlinear quantum optical phenomenon because of the first experimental detection of a quantum state of a light field. Indeed, radiation corresponding to photon antibunching was detected for the first time in scattered light upon the intense excitation by an intense monochromatic light wave [1, 2]. This phenomenon can be explained only within the full quantum-mechanical description of both atomic and field variables [3]. In a usual experiment with the scattering of external monochromatic radiation by a single atom (rarefied atomic medium), fluorescent radiation is studied in the direction perpendicular to a plane formed by the propagation directions of the atomic beam and monochromatic pump light exciting it. Under weak resonance pumping, a single intense elastic scattering peak is detected in radiation scattered by the two-level atom [4]. This peak appears at the resonance transition frequency and its width is determined by the spectral width of pump light and can be much smaller than the natural width of the atomic transition line. As the intensity of the external coherent pump field increases, radiation scattered by the single atom exhibits the known Mollow triplet [5, 6], which includes not only an elastic component, but also a broadened component at the central transition frequency and two less intense broadened satellites whose central frequencies are determined by the Rabi frequency of the external field. This nonlinear phenomenon is determined by the dynamic Stark splitting of atomic levels in the intense external coherent field, when Rabi oscillations modulate the dipole moment of the atomic transition. The half-widths of the incoherent components of the
central and side satellites are different and determined by the half and three-fourths of the natural width of the atomic transition, respectively [7, 8]. The spectral properties of an ensemble of atoms collectively interacting with the external monochromatic coherent pump wave demonstrate features in the optical spectrum of the detected fluorescence signal. In a traditional experiment in the intense pump field whose Rabi frequency
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