Switching from normal to anomalous dispersion in photonic crystal with Raman gain defect.

Propagation of a light through a one-dimensional photonic crystal containing a defect layer doped with a Raman gain medium is discussed. We demonstrate all-optically controlled switching from normal to anomalous dispersion in such a structure. A group delay for the transmitted probe (Raman) pulse is investigated. We show that the group velocity of a Raman pulse can be tuned from subluminal to superluminal by varying the intensity of the pump field.