We study a four-level atomic system with electromagnetically induced transparency with giant ${\ensuremath{\chi}}^{(3)}$ and ${\ensuremath{\chi}}^{(5)}$ susceptibilities of opposite signs. This system will allow us to obtain multidimensional solitons and light condensates with surface tension properties analogous to those of usual liquids.

Turning Light into a Liquid via Atomic Coherence

Coherent control of optical bistability in tunnel-coupled double quantum wells

We propose that a coherently prepared four-level atomic medium can provide a versatile platform for realizing parity-time ($\mathcal{PT}$) symmetric optical potentials. Different types of $\mathcal{PT}$-symmetric potentials are proposed by appropriately tuning the exciting optical fields and the pertinent atomic parameters. Such reconfigurable and controllable systems may open up new avenues in observing $\mathcal{PT}$-related phenomena with appreciable gain-loss contrast in coherent atomic media.

PT-symmetric optical potentials in a coherent atomic medium

Realizing single light bullets and vortices that are stable in high dimensions is a long-standing goal in the study of nonlinear optical physics. The storage and retrieval of such stable high-dimensional optical pulses may offer a variety of applications. Here, we present a scheme to generate such optical pulses in a cold Rydberg atomic gas. By virtue of electromagnetically induced transparency, strong, long-range atom–atom interaction in Rydberg states is mapped to light fields, resulting in a giant, fast-responding nonlocal Kerr nonlinearity and the formation of light bullets and vortices carrying orbital angular momenta, which have extremely low generation power and very slow propagation velocity, and can stably propagate, with the stability provided by the combination of local and nonlocal Kerr nonlinearities. We demonstrate that the light bullets and vortices obtained can be stored and retrieved in the system with high efficiency and fidelity. Our study provides a new route for manipulating high-dimensional nonlinear optical processes via controlled optical nonlinearities in cold Rydberg gases.

Stable single light bullets and vortices and their active control in cold Rydberg gases

Coherent diffusion pertains to the motion of atomic dipoles experiencing frequent collisions in vapor while maintaining their coherence. Recent theoretical and experimental studies on the effect of coherent diffusion on key Raman processes, namely, Raman spectroscopy, slow polariton propagation, and stored light, are reviewed in this Colloquium.

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Colloquium: Coherent diffusion of polaritons in atomic media

We show that a weak probe light beam can form spatial solitons in an electromagnetically induced transparency (EIT) medium composed of four-level atoms and a coupling light field. We find that the coupling light beam can induce a highly controllable nonlinear waveguide and exert very strong effects on the dynamical behavior of the solitons. Hence, in the EIT medium, it is not only possible to produce spatial solitons at very low light intensities but also simultaneously control these solitons by using the coupling-light-induced nonlinear waveguide.

Tao Hong

Papers

Spatial weak-light solitons in an electromagnetically induced nonlinear waveguide.