Ultrasensitive terahertz sensing with high- Q toroidal dipole resonance governed by bound states in the continuum in all-dielectric metasurface

Nanophotonics

article

Yulin Wang¹  Zhanghua Han²  Yong Du¹  Jianyuan Qin¹ 

[1] Center for Terahertz Research, China Jiliang University;School of Physics and Electronics, Shandong Normal University

关键词: all-dielectric metasurface;    bound states in the continuum;    terahertz sensing;    toroidal dipole;   

DOI  :  10.1515/nanoph-2020-0582

学科分类：社会科学、人文和艺术（综合）

来源: De Gruyter

【 摘 要 】

Toroidal dipole (TD) with weak coupling to the electromagnetic fields offers tremendous potential for advanced design of photonic devices. However, the excitation of high quality ( Q ) factor TD resonances in these devices is challenging. Here, we investigate ultrahigh- Q factor TD resonances at terahertz frequencies arising from a distortion of symmetry-protected bound states in the continuum (BIC) in all-dielectric metasurface consisting of an array of high-index tetramer clusters. By elaborately arranging the cylinders forming an asymmetric cluster, two distinct TD resonances governed by BIC are excited and identified. One is distinguished as intracluster TD mode that occurs in the interior of tetramer cluster, and the other one is intercluster TD mode that arises from the two neighboring clusters. Such TD resonances can be turned into ultrahigh- Q leaky resonances by controlling the asymmetry of cluster. The low-loss TD resonances with extremely narrow linewidth are very sensitive to the change in the refractive index of the surrounding media, achieving ultrahigh sensitivity level of 489 GHz/RIU. These findings will open up an avenue to develop ultrasensitive photonic sensor in the terahertz regime.

【 授权许可】

CC BY