Abstract
We have examined the propagation of femtosecond laser pulses in an absorbing dye solution through a short to a long range of propagation distance. The transmitted pulses show strong spectral shift and a superluminal to subluminal transition in the propagation velocity keeping its initial shape almost intact. It is verified that the peak velocity is well described by a modified group velocity defined within the framework of the saddle-point method as well as by a recent prediction of the net group delay of surviving frequency.
- Received 20 October 2000
DOI:https://doi.org/10.1103/PhysRevLett.86.3546
©2001 American Physical Society