Stimulated generation of superluminal light pulses via four-wave mixing

TL;DR

This paper demonstrates the generation of superluminal light pulses with negative group velocities using four-wave mixing, showing controllable pulse propagation speeds that can exceed the speed of light in vacuum.

Contribution

It introduces a method to produce and control superluminal pulses with negative group velocities via four-wave mixing in a medium.

Findings

Generated pulses with negative group velocities up to -1/880c.

Generated pulse peaks can exit the medium ~50 ns earlier than light speed.

Control of group velocities by seed detuning and input power.

Abstract

We report on the four-wave mixing of superluminal pulses, in which both the injected and generated pulses involved in the process propagate with negative group velocities. Generated pulses with negative group velocities of up to $v_{g}=-1/880c$ are demonstrated, corresponding to the generated pulse's peak exiting the 1.7\,cm long medium $\approx50$\,ns earlier than if it had propagated at the speed of light in vacuum, $c$. We also show that in some cases the seeded pulse may propagate with a group velocity larger than $c$, and that the generated conjugate pulse peak may exit the medium even earlier than the amplified seed pulse peak. We can control the group velocities of the two pulses by changing the seed detuning and the input seed power.