Multiple fano resonances based on all-dielectric metastructure for refractive index sensing

• Published in: Infrared physics & technology 2024-06, Vol.139, p.105284, Article 105284
• Main Authors: Guo, Haoyu, Fang, Wenjing, Pang, Jielong, Wang, Tingting, Fan, Xinye, Huang, Yongqing, Bai, Chenglin
• Format: Article
• Language: English
• Subjects: All-dielectric metastructure; BIC; Multiple Fano resonances; Refractive index sensing
• ISSN: 1350-4495; 1879-0275
• DOI: 10.1016/j.infrared.2024.105284

•Refractive index sensor using all-dielectric metasturcture composed of TiO2 rectangles and elliptical cylinder based on SiO2 substrate.•Four sharp resonances of high Q-factor corresponding to multiple resonance modes are analyzed by the near-field distribution of the electromagnetic field.•The sensing performance has been evaluated to achieve the best sensitivity, FOM, and Q-factor simultaneously, reaching 288 nm/RIU, 888RIU−1 and 6900, respectively.•By experimental measurement, the maximum sensitivity is up to 138 nm/RIU, and the modulation depth is about 50 %, demonstrating the feasibility of the experiment. We investigate an optical refractive index sensor based on an all-dielectric metastructure in the near-infrared regime for achieving high sensitivity and high quality factor (Q-factor). By introducing the asymmetry in the metastructure, four sharp Fano resonances with high Q-factor are generated owing to the transition from symmetry-protected bound states in the continuum (BIC) to quasi-BIC, and the magnetic quadrupole (MQ) resonance, magnetic dipole (MD) resonance, and toroidal dipole (TD) resonance are analyzed by a combination of the field distributions. By evaluating the sensing performance with finite difference time domain (FDTD), the highest Q-factor can reach 6900, the modulation depth is close to 100 %, the sensitivity can reach 288 nm/RIU, and the figure of merit (FOM) is 888 RIU−1. Furthermore, the sensor is prepared using electron beam lithography (EBL), and inductively coupled plasma reactive ion etch (ICP-RIE), and high sensitivity is achieved in liquids with different refractive indices in the near-infrared. The results show a good sensing performance of the designed metastructure. Our findings will give access to the development of applications in non-linear devices, narrow-band filters, optical switches, and quantum nanophotonics.