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Quantum Electronics and Laser Science Conference

Coherence and interference enhanced nonlinearities in a four-level system

Jen‐Hao Cheng, Min Yan, Edward G. Rickey, Y. Zhu

Published Jun 25, 2003• 0 citations
Publisher

Abstract

Summary form only given. Nonlinear optical properties of an atomic medium can be modified by coherence and quantum interference that utilizes electromagnetically induced transparency (EIT). Because of the vanishing linear absorption and large enhancement of nonlinearities in an EIT medium, nonlinear optics may be studied at low light levels. We report studies of light absorption and parametric amplification based on the EIT enhanced third-order nonlinearity in a four-level atomic system. We have observed the enhanced nonlinear absorption when two coupling lasers and one probe laser are present. We are in the process of preparing the experiments for the double EIT demonstration and observation of the efficient parametric amplification in the four-level system. Because the experimental system is essentially free of Doppler broadening, quantitative comparisons between the experimental measurements and the theoretical calculations can readily be achieved.

DOI
10.1109/qels.2002.1031230

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We analyze nonlinear excitation in a four-level atomic system that exhibits electromagnetically induced transparency induced by a strong coupling laser. We show that, at the line center of the atomic transition, the nondegenerate two-photon excitation in the dressed states can be enhanced by constructive quantum interference in two excitation paths while the linear absorption is inhibited by destructive quantum interference. We report an experimental study of the interference-enhanced two-photon absorption in a multilevel Λ-type rubidium atomic system and compare the measurements with the theoretical calculations.
Electromagnetically induced transparency (EIT) in a four-level atomic system suppresses linear absorption and leads to resonantly enhanced slow-light four-wave mixing at low light intensities. We analyse the backward four-wave mixing in the four-level system under the EIT conditions, derive the four-wave-mixing efficiency and discuss slow-light propagation conditions. We present experimental measurements of resonant four-wave mixing with the backward scheme in cold Rb atoms and compare the experimental results with the theoretical calculations.