Energy Transport Velocity and the Impression of Superluminal Pulse Propagation

L. J. Wang, Arthur Dogariu, A. Kuzmich

Gerhard Diener

A. Kuzmich, Arthur Dogariu, L.J. Wang +2 more

Lipsa Nanda, Harshawardhan Wanare, S. Anantha Ramakrishna

Anomalous dispersion is at the heart of superluminal pulse propagation in dispersive media. Most earlier analyses of these effects have been confined to discussions of pulse shapes or group velocity and group-velocity dispersion, while experiments typically measure the absorbed energy. We investigate the transport of energy in causal dispersive media including superluminal effects, via the time moments of the Poynting vector. We find that superluminal and negative traversal times are invariably accompanied by an initial temporal compression of the pulse. We predict a crossover distance at which superluminal behavior becomes subluminal even when the spectral width of the initial pulse lies well within the anomalous dispersion region. This effect is generic and we offer a theoretical basis for the experimental results of Talukder et al. [Phys. Rev. Lett. 86, 3546 (2001)]. As the pulse propagates, a strong spectral modification due to dissipation (gain) results in the dominance of normally dispersive spectral components that suffer from lower dissipation (higher gain) and is responsible for this crossover.

Shi‐Yao Zhu, Li‐Gang Wang

In this paper, we discuss what causes the superluminal propagation of a pulse through dispersion by solving Maxwell's equations without any approximation. The coherence of the pulse plays an important role for superluminal propagation. When the pulse becomes partially coherent, the propagation changes from superluminal to subluminal. The energy velocity is always less than the vacuum velocity. The shape of the pulse is changed during the propagation.

朱诗尧, 王立刚

In this paper, we discuss what causes the superluminal propagation of a pulse through dispersion by solving Maxwell's equations without any approximation. The coherence of the pulse plays an important role for superluminal propagation. When the pulse becomes partially coherent, the propagation changes from superluminal to subluminal. The energy velocity is always less than the vacuum velocity. The shape of the pulse is changed during the propagation.