Nonlinear Optics in Resonant Gas Media : Four-Wave Mixing and Higher-Order Processes

Vasily G. Arkhipkin, A. K. Popov

Aleksei M. Zheltikov, Nikolai I Koroteev

A review of the main directions of development, the most promising new techniques, and urgent applications of coherent four-photon methods of investigation of excited and ionized gas media is presented. It is demonstrated that the methods of coherent four-wave mixing (FWM) provide important spectrochronographic information on atoms and ions, allow selective studies of separate components of nonstationary gas and plasma systems with a complex composition using polarization-sensitive four-photon spectroscopy and coherent ellipsometry, and permit nonlinear-optical imaging of the spatial distribution of atoms and ions in excited gases and plasmas.

Kang-Ming Leung

C. Schmidt-Iglesias, Gaspar T. Orriols, Francese Pi

It is shown that very high phase-conjugation efficiency and oscillation is attainable in the saturation regime of resonant degenerate four-wave mixing in Doppler-broadened gas media using transverse optical Zeeman pumping of the ground state as nonlinear mechanism. Our theoretical study predicts also the absence of frequency splitting in the saturated line shape of the vectorially phase-conjugate reflectivity of optically thin media.

M. Ducloy, Daniel Bloch

We present in this paper a theoretical study of the angular dependence of phase-conjugate emission via resonant degenerate four-wave mixing (FWM) in Doppler-broadened gas media. The nonlinear optical polarization is calculated through an expansion of the atomic density matrix up to the third order in the incident fields. One finds that, when the incident frequency is resonant for a single-photon transition, both strength and lineshape of the phase-conjugate emission strongly depend on the angle 0 between standing pump wave and probe wave. The emission intensity, maximum at grazing incidences, decreases rapidly by several orders of magnitude when 0 increases. Simultaneously the emission linewidth increases from homogeneous to Doppler width. Similar effects are predicted for nearly-degenerate FWM (different pump and probe frequencies). In particular, one shows that the bandwidth of the equivalent optical reflection filter undergoes a Doppler-broadening linearly increasing with sin θ. On the opposite, none of the above effects is predicted in two-photon-resonant FWM which does not exhibit any angular dependence.

Mikhail D. Lukin, Philip Hemmer, Marlan O. Scully