Nonlinear characterization of hydrogenated amorphous silicon waveguides and analysis of carrier dynamics

In this paper, we determine the optical nonlinear coefficient of hydrogenated amorphous silicon (a-Si:H) waveguides. Up to date, the data reported in the scientific literature for similar structures show a very large variability and the final assessment of their nonlinear performance is still an open issue. We performed a complete and careful characterization of more than 50 waveguides. A nonlinear coefficient of 790 + j20 W⁻¹ m⁻¹ was found, confirming that a-Si:H is a good candidate for nonlinear silicon photonic devices. Nevertheless, free-carrier-dynamics exhibits a recombination time in the nanosecond range, which can hinder their exploitation in ultrafast applications requiring high-power optical beams.