Improvement of the memory quality of optical pulse pairs in atomic systems via four-wave mixing

We present a scheme to improve the memory quality of linear and nonlinear optical pulse pairs via four-wave mixing (FWM) in an atomic gas. We show that in a linear regime the efficiency and fidelity of the memory of the probe and Stokes pulses can be largely improved through an elimination of the fast-light mode (and hence the suppression of the optical gain induced by the FWM process). We also show that in a nonlinear regime the system may support stable optical soliton pairs with ultraslow propagation velocity and ultralow generation power, which can also be stored and retrieved with a better quality. The improved optical pulse pair memory suggested here may have promising applications in optical information processing and transformation.