Phase-coupling-induced ultraslow light propagation in solids at room temperature

We show that the group velocities of light pulses can be decelerated dramatically by the use of a dispersive phase-coupling effect through a wave mixing process. We have observed experimentally such a phase-coupling-induced ultraslow light propagation with a group velocity as low as 0.05 m/s in a photorefractive Bi12SiO20 crystal at room temperature. Moreover, the ultraslow light is amplified in the Bi12SiO20 crystal because of the unidirectional energy transfer from a coupling beam to the ultraslow light. This technique to produce ultraslow light propagation is valid for all nonlinear wave mixing processes with a dispersive phase-coupling effect.