Evolution of ultra-short optical pulses in active DFB waveguides

We present a time-domain study on propagation of pico-second optical pulses in active semiconductor waveguides embedded with a Bragg grating. The nonlinear effects of gain saturation, limited carrier lifetime, as well as linewidth enhancement factor are taken into account. It is theoretically shown that the effective group velocity can be significantly enhanced by the grating, resulting in the so-called superluminal transmission. Moreover, the pulse propagation and reflection behaviors are greatly influenced by such parameters as Bragg coupling strength and optical gain in the waveguide.