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.
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
