Highly selective four-wave mixing of low-intensity radiation in a degenerate two-level atomic system

Abstract

We derive equations for the collective CDW-current transverse conducting chains in a quasi-one-dimensional CDW conductor. Generalized Fröhlich relations between the transverse currents and phase gradients are due to the polarization corrections to the 1 + 1 chiral anomaly Lagrangian. The CDW Hall constant RCDW is calculated, RCDW ∼ T 2 C /ICDW, where TC is the critical temperature of the Peierls transition, and ICDW is the nonlinear CDW current in the direction parallel to the conducting chains.The Quasi-One-Dimensional (Q1D) Charge Density Wave (CDW) conductors such as NbSe 3 , TaS 3 , K 0,3 MoO 3 etc. (see, for instance, ref.[1]) are characterized by a strongly anisotropic quasiparticle spectrum. As a result, their unusual transport properties are mostly pronounced in the direction parallel to the conducting chains. The theoretical studies of the CDW electrodynamics were mainly focused on the one-dimensional aspect. The response of a 1D CDW is described by the well-known Fröhlich relations [1]

Polarization dependence of four-wave mixing in a degenerate two-level system

“…The width of this resonance is also given at low pump intensities by γ. As already pointed in [8] and [13], this configuration provides the largest ND-FWM yield. The difference in the spectral profile existing between Figs.…”

“…In fact for Ω 1 2Γ the spectral sidebands are barely visible and the spectra is mainly composed by a large central resonance with a width of the order of γ [8]. This configuration produces for Ω 1 ≈ Γ the largest NDFWM yield [13]. For increasing Ω 1 the central peak splits into two components.…”

“…The absorption [9,10] and FWM [11,12] spectra of magneto-optically trapped atoms present characteristic features resulting from the level degeneracy. Recently, the use of DTLS for efficient and highly selective NDFWM generation in an atomic vapor was reported [13].…”

High-quality electromagnetically-induced absorption resonances in a buffer-gas-filled vapour cell

“…The EIA resonance manifests itself as a steep decrease in the cell transparency (see the example in Fig.1). Since its observation, the EIA effect has also found applications, like four-wave mixing [25], "fast" light experiments [26], magnetic field mapping of cold atomic samples [27]; still, until now it has not attracted as much attention as the EIT phenomenon. The main reason that seriously limits the area of EIA use, consists in the problem of obtaining a high-contrast and at the same time sufficiently narrow nonlinear resonance.…”

Two symmetric four-wave mixing signals generated in a medium with anomalous refractive index

“…The nonlinear signals are induced by two independent laser beams, with k a and k b wave-vectors, when both beams are tuned on the same 85 Rb Doppler line 5S 1/2 (F = 3) → 5P 3/2 . In such a case, where all fields are almost resonant with the same optical transition, the degenerate FWM signals have been analyzed considering a pure [14,15] or degenerate two-level system [16], with one strong field, and arbitrary polarization of the drive fields [17,18].…”