Plasmonic anapole metamaterial for refractive index sensing

Electromagnetic anapole mode is a nonradiative state of light originating from the deconstructive interference of radiation of the oscillating electric and toroidal dipole moments. The high quality anapole-related resonances can be used in enhancing nonlinear electromagnetic properties of materials and in sensor applications. In this work, we experimentally demonstrate plasmonic anapole metamaterial sensor of environmental refractive index in the optical part of the spectrum. Our results show that the sensor exhibits high sensitivity to the ambient refractive index at the level of 330 nm/RIU and noise floor of 8.7 × 10-5 RIU. This work will pave the way for applications of anapole metamaterials in biosensing and spectroscopy. Ministry of Education (MOE) Published version This work is supported by the UK Engineering and Physical Science Research Council (grants EP/M009122/1 and EP/ T02643X/1), the Royal Society (grant IEC/R3/170092), the European Research Council (Advanced Grant No. FLEET786851), the Singapore Ministry of Education (N.I.Z.; grant MOE2016-T3-1-006), the University Grants Committee / Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. AoE/P-502/20 and GRF Project: 15303521), the Shenzhen Science and Technology Innovation Commission (Grant No. SGDX2019081623281169), the Department of Science and Technology of Guangdong Province (2020B1515120073), and the City University of Hong Kong (Grant No. 9380131).