Properties of highly-nonlinear hybrid silicon-plasmonic waveguides

Summary form only given. Nonlinear hybrid silicon-plasmonic (HSP) waveguides are comprised of a low-index dielectric with a high nonlinear-index (n₂) occupying the area between a metal and a high-index dielectric, i.e. silicon. Fusing plasmonic and index-contrast guiding mechanisms [1], HSP waveguides can increase the lateral confinement thus boosting the nonlinear parameter (γ); this effect is maximized as the gap between metal and silicon reaches the 10nm-scale and can be exploited in practical integrated circuits. The HSP design incorporates silicon so as to maintain fabrication-compatibility and seamless coupling to the dominant silicon-on-insulator (SOI) platform. However, silicon exhibits two-photon absorption (TPA) below λ=2200nm, which increases the losses and additionally generates free-carriers which, in turn, give rise to secondary nonlinear free-carrier effects (FCE) [2]. The temporal dynamics of FCE are in the 1ns-scale and, above a certain power-threshold, they induce considerable dispersion and absorption (FCD and FCA, respectively) perturbing the guided wave. Both TPA and FCA absorb power thus hindering all χ⁽³⁾-related effects as a whole while FCD counteracts the Kerr-effect and thus imposes an obstacle for this type of nonlinear applications in compact integrated photonic components.