Ultrafast pulse propagation in graphene-comprising nanophotonic waveguides considering nonperturbative electrodynamic nonlinearity

Abstract

We outline a comprehensive model for ultrafast optical pulse propagation along nonlinear graphene-comprising integrated photonic waveguides. An electrodynamic graphene hot-electron model (GHEM) is used to capture the temporal dynamics and intertwined absorptive and refractive nonlinearity to explore a strongly nonperturbative photoconductivity regime that transcends third-order phenomena. We propose a formalism to abstract the 2D material-related modal properties of the waveguides in the static/continuous-wave regime that can also be plugged into a generalized nonlinear Schrödinger equation (NLSE) framework. Our model of optical pulse propagation consists of a coupled NLSE along with the nonlinear equation system of the GHEM. We demonstrate pulsed applications pertinent to integrated photonic components, namely, improvement of the extinction ratio (ER) of a nonreturn-to-zero (NRZ)-modulated bitstream, pulse shaping, spectral broadening, and optical-shock formation leading to pulse breaking and soliton formation. Our NLSE-GHEM extracts graphene nonlinearity from fundamental physics without resorting to phenomenological correction terms or fitted parameters, shows good agreement with recent experiments, and can potentially be used in the study of high-power on-chip applications such as pulsed lasers and frequency combs.