Self-phase-modulation in submicron silicon-on-insulator photonic wires

Abstract

We measure the transmission of ps-pulses through silicon-on-insulator submicron waveguides for excitation wavelengths between 1400 and 1650 nm and peak powers covering four orders of magnitude. Self-phase-modulation induced spectral broadening is found to be significant at coupled peak powers of even a few tens of mW. The nonlinear-index coefficient, extracted from the experimental data, is estimated as n(2) ~ 5*10(-18) m(2)/W at 1500 nm. The experimental results show good agreement with model calculations that take into account nonlinear phase shift, first- and second order dispersion, mode confinement, frequency dispersion of n(2), and dynamics of two-photon-absorption-generated free carriers. Comparison with theory indicates that an observed twofold increase of spectral broadening between 1400 and 1650 nm can be assigned to the dispersion of n(2) as well as first order- rather than second-order dispersion effects. The analysis of pulse broadening, spectral shift and transmission saturation allows estimating a power threshold for nonlinearity-induced signal impairment in nanophotonic devices.

Monolithic nonlinear pulse compressor on a silicon chip

“…The semiconductor nature of silicon implies a small optical band gap, leading to possible nonlinear losses in the form of two-photon absorption (TPA) and free-carrier absorption (FCA). Because of TPA-and FCA-related losses, an input pulse with high peak power experiences a rapid reduction in its amplitude as it propagates into the silicon nanowire waveguide 23,27,28 . As the extent of spectral broadening from self-phase modulation scales with the peak power of the pulse, the reduction in pulse amplitude inside the nanowire waveguide limits the final pulse bandwidth and hence the compression factor.…”

“…functions of both input peak power and dispersive grating length are studied by numerically solving the nonlinear Schrödinger equation 20 , taking into account two photon and free-carrier effects 23,27,28 . The waveguide dispersion and effective waveguide modal area were obtained using a fully vectorial beam propagation method.…”

“…The waveguide dispersion and effective waveguide modal area were obtained using a fully vectorial beam propagation method. The nonlinear refractive index of silicon used to calculate γ from the effective area was varied within the range of reported values [23][24][25][26][27] to obtain the best match to measured data. Experimentally measured values for waveguide propagation losses and grating dispersion were used.…”

“…We report optimal compression factors as high as 7 at a low input peak power of 10 W. The requisite large acquired nonlinear phase for high compression factors is obtained at low input peak powers, owing to the large third order Kerr nonlinearity in silicon, high modal confinement in the carefully designed nanowire waveguide and, consequently, large nonlinear parameter, γ 20,[23][24][25][26] .…”

Effect of Spatial Modulation on Pulse Width for Ultrashort Laser Pulse during Small-Scale Self-Focusing

“…SSSF leaded to off-axis energy moving toward the peak of the pulse and the laser pulse compressed in both space and time, which caused the peak intensity augmenting [5,6]. The increase of peak intensity caused self-phase modulation (SPM) to enhance, which leaded to generating new frequency components [7,8]. If the peak intensity of the laser pulse continually increased, then the combination of the SPM-induced up-chirp and normal group velocity dispersion acted to push the energy away from the peak position, thus initiated the breaking up of the pulse [9,10].…”