Quantum interference effects in ladder-type and Λ-type three-level systems

王正岭, 印建平

Min Yan, Edward G. Rickey, Yifu Zhu

We report experimental studies of electromagnetically induced transparency in Λ-type and ladder-type atomic systems realized in 87Rb atoms cooled and confined in a magneto-optical trap. Complete transparency is observed in the Λ-type system with a moderate coupling field. Comparison between the two systems reveals that at the line center of a weak probe transition, destructive interference occurs for the Λ-type system, whereas constructive interference occurs for the ladder-type system. We discuss conditions of complete transparency in the Λ-type system that contains hyperfine magnetic sublevels. Our experimental measurements for the two systems agree with theoretical calculations based on simple three-level Λ-type and ladder-type models.

Kariman I. Osman, Saad S. M. Hassan

Seyyed Hossein Asadpour, Ziauddin Ziauddin, Muqaddar Abbas +1 more

The noise-induced coherence created via the quantum interference of incoherent radiation in atomic three-level systems of V and \ensuremath{\Lambda} types driven by a pair of weak laser pulses is shown to result in exchange of optical vortices. In the three- level V-type atom-light coupling the system is populated in its ground level, while in the \ensuremath{\Lambda} model the system is initially prepared in an electromagnetically induced transparency state. By solving the quantum optical Maxwell-Bloch equations and with quantum interference of incoherent radiation present, we show that the orbital angular momentum (OAM) of the vortex probe beam can be transferred to a generated signal field. While the exchange efficiency in the V configuration is higher, the losses are less in the \ensuremath{\Lambda} scheme when we consider such a noise-induced coherence. We further discuss the effects of phase mismatching and inhomogeneous broadening on the energy conversion between light beams carrying OAM.

Liu Zhi-Yuan, Yupeng Duan, Ying-Jie Du

Abstract We theoretically investigate the self-nonlinear and cross-nonlinear responses of the Λ-type, V-type, and ladder-type three-level atomic systems. The analytical solutions of the cross-nonlinearity are obtained by using an iterative method. These analytical expressions reveal that the atomic decay rates and two-photon resonance are closely related to the cross-nonlinear response. For the Λ-type system, the relaxation rate between the ground-state sublevels determines the amplitude and linewidth of the cross-nonlinearity. For the ladder-type system, the lifetime of the upper excited state governs the amplitude and linewidth of the cross-nonlinearity. In both systems, the amplitude of the cross-nonlinearity is significantly enhanced, and the linewidth is greatly compressed simultaneously. In contrast, for the V-type three-level system, the amplitude and linewidth of the cross-nonlinearity are related to the spontaneous emission rate of the excited states, where neither the amplitude enhancement nor the linewidth compression is observed. We conclude that the cross-nonlinear response can reach or even exceed the linear response in the Λ-type system when the relaxation rate between the ground states is sufficiently small, or in the ladder-type system when the spontaneous emission rate of the upper excited state is sufficiently small. Compared with the crossnonlinearity, the self-nonlinearity is related to the Rabi frequency and detuning of the coupling field. Its amplitude decreases with the increase of the coupling Rabi frequency, while it can be increased to a certain extent with the increase of the coupling detuning. Our results provide a theoretical basis for the optimization and application of strong nonlinear effects in three-level atomic systems.

M.I. Podgoretskii, O.A. Khrustalev