Six-wave mixing induced by free-carrier plasma in silicon nanowire waveguides

TL;DR

This paper demonstrates six-wave mixing induced by free-carrier effects in silicon nanowire waveguides, revealing unique nonlinear interactions and phase-sensitive phenomena, expanding understanding of multi-wave mixing in nanoscale photonics.

Contribution

It provides the first experimental demonstration of free-carrier-induced six-wave mixing in silicon nanowires, with analytical and numerical validation of unique nonlinear features.

Findings

Inverse detuning dependence of six-wave-mixing efficiency

Higher sensitivity of six-wave mixing to pump power

Asymmetric sideband generation due to phase interactions

Abstract

Nonlinear wave mixing in mesoscopic silicon structures is a fundamental nonlinear process with broad impact and applications. Silicon nanowire waveguides, in particular, have large third-order Kerr nonlinearity, enabling salient and abundant four-wave-mixing dynamics and functionalities. Besides the Kerr effect, in silicon waveguides two-photon absorption generates high free-carrier densities, with corresponding fifth-order nonlinearity in the forms of free-carrier dispersion and free-carrier absorption. However, whether these fifth-order free-carrier nonlinear effects can lead to six-wave-mixing dynamics still remains an open question until now. Here we report the demonstration of free-carrier-induced six-wave mixing in silicon nanowires. Unique features, including inverse detuning dependence of six-wave-mixing efficiency and its higher sensitivity to pump power, are originally observed and verfied by analytical prediction and numerical modeling. Additionally, asymmetric sideband generation is observed for different laser detunings, resulting from the phase-sensitive interactions between free-carrier six-wave-mixing and Kerr four-wave-mixing dynamics. These discoveries provide a new path for nonlinear multi-wave interactions in nanoscale platforms.