Article révisé par les pairs
Résumé : Nondegenerate two-photon absorption (ND TPA) is studied in a nanophotonic silicon waveguide in a configuration such that the dispersion of the nonlinear absorption and refraction cannot be ignored. It is shown that a signal wave around 1330 nm can be strongly absorbed by ND TPA with a pulse of 6-W peak power at 1850 nm. Experiments are performed with pulses of about 200 fs in a dispersion engineered waveguide in which the pump and signal pulses propagate at a similar group velocity. The experimental results are very well reproduced by numerical simulations of two coupled generalized nonlinear Schrödinger equations (GNLSEs). We show that the nonlinear dynamics can be well described by a single GNLSE despite the wavelength separation between the pump and the signal waves. We also demonstrate that in silicon nanophotonic waveguides, the dispersion of the nonlinear absorption is much larger than the dispersion of the Kerr effect. This could have an impact in the design of all-optical functions based on ND TPA, as well as on the study of supercontinuum and frequency-comb generation in integrated semiconductor-on-insulator platforms.