We demonstrate how both normal and anomalous dispersion can be realized concurrently for a pair of weak probes in a doubly driven double-ladder configuration with independent and simultaneous control for group velocities of the pair. We have shown both analytically and numerically that, because of electromagnetically induced transparency and a χ((3))-based gain process, a slow-fast light pair can be realized in the same delay element with group indices ∼±10(7) accompanied by gain or relatively small absorption (down to ∼25%). We also identify parameter regions for realization of concurrent slow-slow and fast-fast light pairs with reduced absorptions.
© 2011 Optical Society of America