Characterization of optical nonlinearities in nanoporous silicon waveguides via pump-probe heterodyning technique.

The nonlinear response of nanoporous silicon optical waveguides is investigated using a novel pump-probe method. In this approach we use a two-frequency heterodyne technique to measure the pump-induced transient change in phase and intensity in a single measurement. We measure a 100 picosecond material response time and report behavior matching a physical model dominated by free-carrier effects significantly stronger than those observed in traditional silicon-based waveguides.