Superluminal optical pulse propagation in nonlinear coherent media

Abstract

The propagation of light-pulse with negative group-velocity in a nonlinear medium is studied theoretically. We show that the necessary conditions for these effects to be observable are realized in a three-level $\Lambda$-system interacting with a linearly polarized laser beam in the presence of a static magnetic field. In low power regime, when all other nonlinear processes are negligible, the light-induced Zeeman coherence cancels the resonant absorption of the medium almost completely, but preserves the dispersion anomalous and very high. As a result, a superluminal light pulse propagation can be observed in the sense that the peak of the transmitted pulse exits the medium before the peak of the incident pulse enters. There is no violation of causality and energy conservation. Moreover, the superluminal effects are prominently manifested in the reshaping of pulse, which is caused by the intensity-dependent pulse velocity. Unlike the shock wave formation in a nonlinear medium with normal dispersion, here, the self-steepening of the pulse trailing edge takes place due to the fact that the more intense parts of the pulse travel slower. The predicted effect can be easily observed in the well known schemes employed for studying of nonlinear magneto-optical rotation. The upper bound of sample length is found from the criterion that the pulse self-steepening and group-advance time are observable without pulse distortion caused by the group-velocity dispersion.

arXiv comment16 pages, 7 figures

References in corpus (6)

• Storage of light in atomic vapor
• Ultra-Slow Light and Enhanced Nonlinear Optical Effects in a Coherently Driven Hot Atomic Gas
• Resonant nonlinear magneto-optical effects in atoms
• Transparent Anomalous Dispersion and Superluminal Light Pulse Propagation at a Negative Group Velocity
• Enhancement of Magneto-Optic Effects via Large Atomic Coherence
• Superluminal Optical Phase Conjugation: Pulse Reshaping and Instability

Cited by in corpus (4)

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• Lossless anomalous dispersion and an inversionless gain doublet via dressed interacting ground states (DIGS)
• Dirac tachyons and antitachyons in many-particle system