Distortion and attenuation free gain-assisted Superluminal Propagtion in a Rare-Earth Doped Crystal
A light pulse that travels through a narrow spectral window, i.e. a frequency range of low absorption, within a strongly absorbing frequency range will be delayed due to strong dispersion. If however, the absorbing structure is inverted, such that it is amplifying instead, one will see that a pulse travelling through this window will have its pulse peak come out of the material before it is sent i
