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Optical Coherent Transients in Cold Atoms: From Free-Induction Decay to Optical Precursors

Authors Chen, Jiefei HKUST affiliated (currently or previously)
Wang, Shuyuan HKUST affiliated (currently or previously)
Wei, Dong HKUST affiliated (currently or previously)
Loy, Michael Ming-tak View this author's profile
Wong, George K L View this author's profile
Du, Shengwang View this author's profile
Issue Date 2010
Source Physical Review A , v. 81, (3), March 2010, Article number 033844
Summary We report theoretical and experimental studies of the propagation of a square-modulated laser pulse through a laser-cooled atomic ensemble of two-level absorbers, as well as through a three-level system with electromagnetically induced transparency. We find that the transmission characteristics over a wide range of optical depth can be fully accounted for as optical coherent transients excited by the wide spectral content of the square-modulated optical pulse. We show that both time-domain atom-field coupled equations and frequency-domain linear dispersion theory give precisely the same description of the optical transients at a weak power limit. At low optical depth with moderate absorption, resonant excitation dominates and free-induction decay (FID) contributes mostly to the transient field. At high optical depth when absorption and propagation effects become significant, lossless optical precursors start to dominate the transient response. By varying the optical depth from 0 to 45, we observe that optical transients evolve gradually from FID to optical precursors. We thus show that FID and optical precursors, which have been considered as two different optical transients for many decades, can be unified within a single theoretical frame and they are the manifestations of the same physical process in two different regimes.
ISSN 1050-2947
Rights © 2010 American Physical Society
Language English
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