Terahertz nonlinear conduction and absorption saturation in silicon waveguides

TL;DR

This study demonstrates terahertz-induced nonlinear conduction and absorption saturation in silicon waveguides, revealing hot carrier effects and modeling the phenomena with a nonlinear Drude approach validated by simulations.

Contribution

It introduces a nonlinear dynamical model of Drude conductivity for terahertz interactions in silicon, supported by experimental and simulation validation.

Findings

Absorption saturates under strong terahertz fields

Hot carriers significantly influence nonlinear conduction

Model accurately reproduces experimental observations

Abstract

We employ a silicon dielectric waveguide to confine and concentrate terahertz pulses, and observe that the absorption saturates under strong terahertz fields. By comparing the response between lightly-doped and intrinsic silicon waveguides, we confirm the role of hot carriers in this saturable absorption. We introduce a nonlinear dynamical model of Drude conductivity that, when incorporated into a wave propagation equation, accurately reproduces the observations and elucidates the physical mechanisms underlying this nonlinear effect. The results are numerically confirmed by Monte Carlo simulations of the Boltzmann transport equation, coupled with split-step nonlinear wave propagation.