Phase control of stationary light pulses due to a weak microwave coupling

We study the dynamic control of stationary light pulses generated in a sample of cold atoms driven into the double- Λ configuration with two ground levels coupled by a weak microwave field. This microwave field can modify the spin coherence of two ground levels through its phase and amplitude, and then increase or decrease the intensity of a stationary light pulse generated from this spin coherence. Such phase-modulation technique is essential to maximize the effective interaction time between light and matter in photonic information processing and therefore facilitate the achievement of enhanced optical nonlinearities at low-light levels.