Revised theory of resonant degenerate four-wave mixing with broad-bandwidth lasers

J. Cooper, A. Charlton, D. R. Meacher, P. Ewart, and G. Alber
Phys. Rev. A 40, 5705 – Published 1 November 1989
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Abstract

We present a revision of the theory of finite laser bandwidth effects on degenerate four-wave mixing (DFWM) of Alber, Cooper, and Ewart (ACE) [Phys. Rev. A 31, 2344 (1985)]. The same model is used for intense, broad-bandwidth pump lasers interacting with a weak monochromatic probe in a medium composed of two-level atoms. The density-matrix equations describing the time evolution of the atomic polarization coupled to fluctuating fields are solved using an appropriate decorrelation approximation. A steady-state analytical solution is found for resonant and near-resonant DFWM, for intensities that do not saturate the medium. For more intense fields it is found to be necessary to form a more complicated set of differential equations for all products of the field and atomic density-matrix elements. The results show that as in the ACE theory, increasing the bandwidth b leads to an increased effective saturation intensity. However, we find the DFWM reflectivity scales as 1/b2 when the probe is monochromatic and not 1/b as in the ACE theory. Furthermore, the saturation behavior of nonresonant DFWM is found to differ from the predictions of ACE. Atomic motion effects are shown to yield a Doppler-broadened line shape and also to affect the saturation behavior of the signal.

  • Received 16 May 1989

DOI:https://doi.org/10.1103/PhysRevA.40.5705

©1989 American Physical Society

Authors & Affiliations

J. Cooper

  • Joint Institute for Laboratory Astrophysics, University of Colorado
  • National Institute of Standards and Technology, Boulder, Colorado 80309-044 0

A. Charlton, D. R. Meacher, and P. Ewart

  • Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom

G. Alber

  • Faculty of Physics, Albert Ludwigs University, Hermann Herder Strasse 3D, 7800 Freiburg, Federal Republic of Germany

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Issue

Vol. 40, Iss. 10 — November 1989

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