Ultrafast-pulse self-phase modulation and thirdorder dispersion in Si photonic wire-waveguides

By propagating femtosecond pulses inside submicron-cross-section Si photonic-wire waveguides with anomalous dispersion, we demonstrate that the pulse-propagation dynamics is strongly influenced by the combined action of optical nonlinearity and up to third-order dispersion with minimal carrier effects. Because of strong light confinement, a nonlinear phase shift of a few π due to self-phase modulation is observed at a pulse peak-power of just ∼250 mW. We also observe soliton-emitted radiation, fully supported by theoretical analysis, from which we determine directly the third-order dispersion coefficient, β₃ = -0.73 ± 0.05 ps ³/m at 1537 nm.