Arbitrary delay-time control of ultraslow matched pulses

Abstract

We have theoretically and experimentally analyzed the ultraslow matched-pulse propagation in a parametric amplifying medium, especially focusing on the delay-time behaviors of the input probe pulse (signal) and the generated Stokes pulse (idler) under a strong coupling beam. Theoretically, it is predicted that the Stokes pulse always propagates with a definite group velocity with some initial delay time. The probe pulse, on the other hand, propagates at a fixed delay from Stokes after some transient period. This additional delay time is positive (probe is behind Stokes) if the medium is opaque for probe and transparent for Stokes, or it can be negative (probe is ahead of Stokes), if otherwise. It is also shown that the delay times of probe and Stokes, including the order of the pulses, can be arbitrarily and independently controlled by external parameters. The theoretical predictions and numerical simulations have been compared with experimental observations using a hot sodium vapor and they had a very nice agreement.