Enhanced group velocity of ultrashort optical pulses in Bragg grating waveguide structure

Theoretical investigation using both time-domain and frequency-domain methods shows that effective group velocity in optical waveguides can be significantly enhanced by a Bragg grating, so that picosecond optical pulses whose spectrum is located around Bragg bandgap center, can travel 2.6 times as fast compared with the case without grating. Moreover, we point out that this enhanced group velocity can be controlled by the carrier-induced optical gain. This last effect is induced through a linewidth enhancement factor, which detunes pulse wavenumber from the center of Bragg bandgap, where pulse transmission is the fastest. This may imply interesting applications, such as an electronically controlled optical delay in optical transmission systems.