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Science 12 May 2006:
Vol. 312. no. 5775, pp. 895 - 897
DOI: 10.1126/science.1124524
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Reports

Observation of Backward Pulse Propagation Through a Medium with a Negative Group Velocity

George M. Gehring,1* Aaron Schweinsberg,1 Christopher Barsi,3 Natalie Kostinski,1,4 Robert W. Boyd1,2

The nature of pulse propagation through a material with a negative value of the group velocity has been mysterious, as simple models seem to predict that pulses will propagate "backward" through such a material. Using an erbium-doped optical fiber and measuring the time evolution of the pulse intensity at many points within the fiber, we demonstrate that the peak of the pulse does propagate backward inside the fiber, even though the energy flow is always in the forward direction.

1 Institute of Optics, University of Rochester, Rochester, NY 14627, USA.
2 Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA.
3 Department of Electrical and Computer Engineering, Manhattan College, New York, NY 10471, USA.
4 Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA.

* To whom correspondence should be addressed. E-mail: gehring{at}optics.rochester.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Controlling the Velocity of Light Pulses.
R. W. Boyd and D. J. Gauthier (2009)
Science 326, 1074-1077
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Science. ISSN 0036-8075 (print), 1095-9203 (online)