Pulse Evolution and Phase Sensitive Amplification in Silicon Waveguides
  We for the first time provide an analytic solution for pulse propagation and phase sensitive amplification in the regime of high nonlinearity in silicon waveguides including two-photon absorption (TPA) and free carriers. Our analytic results clearly explain why and how the TPA and free carriers affect the signal gain. These observation are confirmed with numerical modelling and experimental results. 
Yanbing Zhang, Chad Husko, Jochen Schroder, and Ben J. Eggleton
physics.optics