Strategies to enhance THz harmonic generation combining multilayered, gated, and metamaterial-based architectures

TL;DR

This paper presents innovative multilayered, gated, and metamaterial-based graphene architectures that significantly enhance terahertz harmonic generation, demonstrating over thirtyfold improvements and potential for advanced THz signal processing.

Contribution

It introduces combined strategies of multilayering, electrical gating, and metasurface modulation to substantially boost THz nonlinearities in graphene, surpassing previous approaches.

Findings

THG enhancement factors exceeding thirty

Architectures capable of two-order-of-magnitude increase

Potential applications in THz frequency conversion technologies

Abstract

Graphene has unique properties paving the way for groundbreaking future applications. Its large optical nonlinearity and ease of integration in devices notably makes it an ideal candidate to become a key component for all-optical switching and frequency conversion applications. In the terahertz (THz) region, various approaches have been independently demonstrated to optimize the nonlinear effects in graphene, addressing a critical limitation arising from the atomically thin interaction length. Here, we demonstrate sample architectures that combine strategies to enhance THz nonlinearities in graphene-based structures. We achieve this by increasing the interaction length through a multilayered design, controlling carrier density with an electrical gate, and modulating the THz field spatial distribution with a metallic metasurface substrate. Our study specifically investigates third harmonic generation (THG) using a table-top high-field THz source. We measure THG enhancement factors exceeding thirty and propose architectures capable of achieving a two-order-of-magnitude increase. These findings highlight the potential of engineered graphene-based samples in advancing THz frequency conversion technologies for signal processing and wireless communication applications.