Effect of free carrier on high repetition rate pulse trains in silicon nanowire waveguides

By using the finite difference method, the nonlinear effects of high repetition rate femtosecond pulse trains in silicon nanowire waveguides were analyzed. By numerically modeling the propagation of femtosecond pulse in silicon nanowire waveguides with the generalized nonlinear Schrödinger equation, the temporal and spectral properties of femtosecond pulses propagating are discussed, and the physical mechanisms of pulse evolution are demonstrated. The simulation results indicate that, owing to the remarkable nonlinear effect, the carriers in the silicon waveguide are rapidly excited with the increase of the input laser power, subsequently have significant modulation effects on the high repetition rate pulses train. For various repetition rate and power of the laser pulses train, the output pulsestrain will get different temporal compression and broadening under the dominance of different nonlinear effects. Furthermore, the results demonstrate that the spectrum evolution of pulse train with different transmission distances is similar to the calculated results of single pulse transmission. The results will provide an important reference for the design of optical sampling clock, microwave photonic radar system and the sweep of carriers in waveguide.