Knob for changing light propagation from subluminal to superluminal

The application of a coupling field connecting the two lower metastable states of a system was shown to produce a variety of effects on the propagation of a weak electromagnetic pulse. The experiments were based on the fact that electromagnetically induced transparency lead to a dispersion profile with a sharp derivative near the line center of the absorption line. It was found that the pulse was narrowed compared to the input pulse. Results indicated that the application of lower level coupling field can lead to superluminal propagation.

Overview