When slowly moving light beam passes through a target sample, the interaction time of the beam with the medium and hence its effective optical length increases. This enables the possibility of enhancing spectroscopic signals by 1-2 orders of magnitude. It is observed that both slow and fast light can be realized simultaneously for a pair of weak probes in a doubly driven double-ladder configuration with independent and simultaneous control for group velocities of the pair. It is shown that keys to realization of the simultaneous slow-fast light are electromagnetically induced transparency and X~((3))-based gain process. Many interesting parameter domains are identified where concurrent slow-slow and fast-fast light pairs can also be realized. The pair of controlled group velocities could be useful for simultaneous optical-length control of two absorption lines.
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