Absorption spectrum of an atom strongly coupled to a high-temperature reservoir

Journal Article · Tue Mar 01 00:00:00 EST 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.71.033806· OSTI ID:20650488

Kofman, A G ^[1]

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1. Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100 (Israel)

We study the absorption spectrum of a weak probe field near resonant to an atomic transition, the upper level of which is strongly coupled to a third level by the interaction with a Lorentzian bosonic reservoir, such as, e.g., a mode of a high-Q cavity or a local vibration in a solid. The reservoir coupling is approximated by the interaction with a classical complex Gaussian-Markovian random process (control field), which is justified when the reservoir temperature exceeds significantly the mode frequency or when the high-Q cavity is pumped by broadband incoherent radiation. The present theory is applicable also when the control field is chaotic laser light. We assume that the rms control-field Rabi frequency V{sub 0} is much greater than the field detuning {delta}{sub c}, which, in turn, is much greater than the material relaxation constants. We reveal and describe analytically all qualitatively different regimes of the spectrum modification and obtain their validity conditions. The analytical results are verified by numerical calculations using the exact continued-fraction solution. The analytical formulas obtained allow one to perform fast computer calculations for arbitrarily small values of the reservoir (control-field) bandwidth {nu}, in contrast to the known numerical methods, which require sharply increasing computational resources with a decrease of {nu}. In the most interesting case {nu}<<V{sub 0}, the spectrum consists of two peaks, the nonvanishing bandwidth and material relaxation affecting mainly the dip between the peaks. The results obtained in the static limit (i.e., a very narrow reservoir) are independent of the reservoir band shape. We reveal reservoir-induced transparency (RIT) - i.e., absorption reduction due to the reservoir coupling. Moreover, two unexpected, remarkable features are uncovered in a range of intermediate values of {nu} and V{sub 0}, {gamma}{sup 2} vertical bar {delta}{sub c} vertical bar<<V{sub 0}{sup 2}{nu}<< vertical bar {delta}{sub c} vertical bar{sup 3} ({gamma} is the spectral width in the absence of the control field): an extra peak in the dip and a resonance-absorption decrease by a half (i.e., an increase of RIT) relative to the static limit. The existence of the above spectral features depends on the statistical details of the control-field temporal behavior.

• OSTI ID: 20650488
• Journal Information: Physical Review. A, Vol. 71, Issue 3; Other Information: DOI: 10.1103/PhysRevA.71.033806; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
ABSORPTION SPECTRA
ATOMS
CHAOS THEORY
COMPUTER CALCULATIONS
CONTINUED FRACTIONS
COUPLING
LASER RADIATION
MARKOV PROCESS
MATHEMATICAL SOLUTIONS
OPACITY
OPTICS
PHOTON-ATOM COLLISIONS
PROCESS CONTROL
QUANTUM MECHANICS
RANDOMNESS
RELAXATION
SOLIDS
VISIBLE RADIATION