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Journal of Optics B Quantum and Semiclassical Optics

Degenerate four-wave mixing in a dense two-level system embedded in a dielectric medium

Ka-Di Zhu

Published Apr 18, 2001• 0 citations
Publisher

Abstract

The nonlinear absorption and reflection spectra of a degenerate four-wave mixing (DFWM) in a dense collection of two-level atoms embedded in a linear dielectric medium are investigated theoretically in terms of the slowly varying envelope approximation and the undepleted pump approximation. The numerical results show that the linear dielectric host is beneficial to the DFWM reflection spectra of a dense two-level atom system embedded in a linear dielectric medium.

DOI
10.1088/1464-4266/3/3/307

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The nonlinear absorption and reflection spectra of a degenerate four-wave mixing (DFWM) in a dense collection of two-level atoms embedded in a linear dielectric medium are investigated theoretically in terms of the slowly varying envelope approximation and the undepleted pump approximation. The numerical results show that the linear dielectric host is beneficial to the DFWM reflection spectra of a dense two-level atom system embedded in a linear dielectric medium.
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We study phase-conjugate degenerate four-wave mixing (DFWM) in an optically pumped, two-level atomic system (the 3s2S1∕23s\phantom{\rule{0.2em}{0ex}}^{2}S_{1∕2}3s2S1∕2​, F=2F=2F=2, ${m}_{F}=2\ensuremath{\rightarrow}3p\phantom{\rule{0.2em}{0ex}}^{2}P_{3∕2}$, F=3F=3F=3, mF=3{m}_{F}=3mF​=3 transition in a diffuse, collision-free, thermal beam of sodium) using phase-modulated laser beams. In this investigation, we study the detailed line shape of the four-wave mixing signal as a function of the temporal delay between the probe field and the pump fields at different intensities of the cw pump waves and modulation frequencies. We show that phase modulation of the pump and probe beams leads to strong amplitude modulation of the phase-conjugate beam and report excellent agreement between our experimental observations of the DFWM spectra and the results of numerical calculations. Our numerical results suggest an enhancement of the ``local'' DFWM signal when the sidebands of the phase-modulated laser are resonant with dressed-state transitions, but that this resonance is less obvious in the total signal generated. We also show that the complex line shapes depend sensitively upon the delay of the probe beam, with the peak DFWM signal occurring when the probe beam is advanced compared to the pump beam.
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