Dispersive effect of light phase coupling and group velocity control in solids at room temperature

A new mechanism to control the group velocity of light based on the dispersive effect of phase coupling has been developed, by means of which we have realized ultraslow and superluminal light propagation in photorefractive Bi12SiO20 crystal at room temperature through the photorefractive phase coupling effect. The ultraslow and superluminal light were shown to be amplified due to photorefractive intensity coupling in the crystal.