Stuttgart 2012 – wissenschaftliches Programm
Q 69.7: Vortrag
Freitag, 16. März 2012, 15:30–15:45, V38.04
Superluminal Twin Beams, Superluminal Images and the Arrival Time of Spatial Information in Optical Pulses with Negative Group Velocity — •Ulrich Vogl, Ryan T. Glasser, and Paul D. Lett — Joint Quantum Institute, NIST and the University of Maryland, Gaithersburg, MD 20899 USA
We report the demonstration of superluminal pulse generation via noncollinear four-wave mixing in hot rubidium vapor with a double-Λ scheme. Two steep gain features result in a large dispersion near the gain lines, resulting in both slow and fast light effects. We identify large negative group indices in the wings of the gain line and observe group velocities of up to -1/2000 c for the injected beam. A novel feature of this system is that the generated conjugate can also be superluminal, and that the group velocity of both the probe and the conjugate can be tuned over a wide range via the probe’s two-photon detuning and also via the probe power. In another experiment we imprint spatial patterns on the probe pulse. We show that anomalous dispersion can be used as an additional degree of freedom for image processing, complementary to existing schemes to slow down and store images. This scheme allows us also to investigate the propagation of spatial information through a medium of anomalous dispersion. By doing this we can address the velocity of information without introducing temporal waveforms with a frequency bandwidth outside the region of anomalous dispersion. Prospects include the investigation of correlations between the generated twin beams when passed through an anomalous dispersion medium.