AUTHOR=Wang Baoku , Liu Jing , Cui Jinhui , Liu Jialin , Tian Fengjun , Sun Weimin , Li Li 

TITLE=Enhanced terahertz third-harmonic generation by bound states in the continuum in graphene grating-like metamaterial

JOURNAL=Frontiers in Physics

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2023.1135211

DOI=10.3389/fphy.2023.1135211

ISSN=2296-424X

ABSTRACT=<p>Non-linear metamaterials hold great promise for enhanced terahertz harmonic generation. Here, we numerically investigate enhanced terahertz third-harmonic generation (THG) by exploiting the symmetry-protected bound states in the continuum (BICs) in graphene grating-like metamaterial. By symmetry breaking of metamaterials, BICs transform into quasi-BICs. The high Q-factor and strong localized field enhancement is achieved at quasi-BICs, leading to a boosted THG process with low incident intensity of fundamental frequency. The THG conversion efficiency reaches 3.1% at an incident intensity of 100 kW/cm<sup>2</sup>. The remarkably enhanced non-linear optical process in the proposed non-linear metamaterial constitutes an outstanding platform for on-chip terahertz non-linear conversion applications.</p>