Enhanced THz third-harmonic generation in graphene via hot-carriers in a topological cavity

TL;DR

This paper demonstrates enhanced third-harmonic generation in graphene integrated with topological photonic crystals, emphasizing the role of hot-carrier effects and thermodynamics in boosting nonlinear THz responses for advanced optoelectronic applications.

Contribution

It introduces a coupled simulation framework that accurately models hot-carrier effects in graphene within topological cavities, revealing new mechanisms for THG enhancement.

Findings

Carrier heating significantly increases THG efficiency.

Hot-carrier effects modulate third-order conductivity.

Design achieves high conversion at moderate intensities.

Abstract

Graphene is a promising material for nonlinear THz applications owing to its high third-order susceptibility and tunable optical properties. Its strong nonlinear response, driven by free-carrier thermodynamics, facilitates efficient third-harmonic generation (THG), which can be further enhanced using resonant metasurfaces and plasmonic structures. In this study, we use a platform that integrates graphene ribbons at the interface of topological photonic crystals designed to boost THG at low THz frequencies. To accurately capture the temperature dependence of the nonlinear optical response, we perform coupled simulations to model graphene's optical and thermodynamic responses under THz photoexcitation, incorporating photoinduced hot carrier effects within a multiphysics computational framework. This approach unveils the influence of carrier heating on THG, providing a more accurate description of nonlinear THz processes and revealing previously overlooked mechanisms of third-order conductivity modulation. We show that the elevated carrier temperature promotes high conversion efficiencies at moderate input intensities, within a design that operates in both reflection and transmission modes for advanced ultrafast optoelectronic devices in the THz regime.