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| Gain-assisted superluminal light propagation |
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| Author(s): Wang LJ, Kuzmich A, Dogariu A |
| Source: NATURE Volume: 406 Issue: 6793 Pages: 277-279 Published: JUL 20 2000 |
| Times Cited: 522 References: 25 |
| Abstract: Einstein's theory of special relativity and the principle of causality(1-4) imply that the speed of any moving object cannot exceed that of light in a vacuum (c). Nevertheless, there exist various proposals(5-18) for observing faster-than-c propagation of light pulses, using anomalous dispersion near an absorption line(4,6-8), nonlinear(9) and linear gain lines(10-18), or tunnelling barriers(19). However, in all previous experimental demonstrations, the light pulses experienced either very large absorption(7) or severe reshaping(9,19), resulting in controversies over the interpretation. Here we use gain-assisted linear anomalous dispersion to demonstrate superluminal light propagation in atomic caesium gas. The group velocity of a laser pulse in this region exceeds c and can even become negative(16,17), while the shape of the pulse is preserved. We measure a group-velocity index of n(g) = -310(+/-5); in practice, this means that a light pulse propagating through the atomic vapour cell appears at the exit side so much earlier than if it had propagated the same distance in a vacuum that the peak of the pulse appears to leave the cell before entering it. The observed superluminal light pulse propagation is not at odds with causality, being a direct consequence of classical interference between its different frequency components in an anomalous dispersion region. |
| Document Type: Article |
| Language: English |
| Reprint Address: Wang, LJ (reprint author), NEC Res Inst, 4 Independence Way, Princeton, NJ 08540 USA |
Addresses:
1. NEC Res Inst, Princeton, NJ 08540 USA |
| Publisher: MACMILLAN PUBLISHERS LTD, PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND |
| Subject Category: Multidisciplinary Sciences |
| IDS Number: 335PM |
| ISSN: 0028-0836 |
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