Nonlinearities in porous silicon optical waveguides at 1550 nm

We report an experimental investigation of the nonlinear optical properties of nanoporous silicon optical waveguides measured at 1550 nm. The nonlinear properties including two-photon absorption, self-phase modulation, free-carrier absorption and free-carrier plasma dispersion are characterized and compared with similar measurements conducted on a conventional silicon-on-insulator ridge waveguide. Our study reveals that even waveguides that are 70% porous exhibit two-photon absorption and self-phase modulation coefficients that are comparable to those of crystalline silicon. The free-carrier absorption and dispersion in porous silicon waveguides are found to be significantly faster, and stronger than those reported for crystalline silicon.