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 vg = −c/880 are demonstrated, corresponding to the generated pulses peak exiting the 1.7 cm long medium ~50 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 faster 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 via the seed detuning and the input seed power.
Physical Review Letters
atomic vapor, Four-wave mixing, negative group velocity, nonlinear optics, superluminal