We analyze a lifetime-broadened four-state, ladder-type four-wave mixing (FWM) scheme in the context of optical soliton formation. We show that a pulsed probe field and a pulsed FWM field of considerably different frequency can evolve into a pair of matched solitons with the same temporal shape and ultraslow group velocity $(V_g∕c\sim {10}^{-3})$, i.e., two-color ultraslow optical solitons. In addition, we show regimes where two-color superluminal $(V_g∕c<0)$ optical soliton propagation may occur.

• Received 19 September 2004

DOI:https://doi.org/10.1103/PhysRevA.71.053820