Strong field enhancement and hot spot manipulation based on anapole state in Si disk-ring metasurface

In this work, a metasurface consisting of disk-ring Si nanostructures on a SiO2 substrate is proposed and numerically simulated. The Si disk-ring structure can excite and manipulate anapole state, and periodic array supports lattice resonance simultaneously, which can improve the near-field enhancement in the gap region. The maximum E-field enhancement can be up to 346 times, and a transmission dip with an ultra-narrow bandwidth of 0.34 nm and a Q-factor of 4460 is shown. When the central disk has an offset, the near-field enhancement can be affected. In the case of y-direction offset, the maximum E-field enhancement can be up to 468 times. The near field energy is concentrated in the gap region, easy to interact with probing molecule in surrounding environment. Meanwhile, the designed metasurface shows a sensing performance of 387 nm/RIU. The strong energy confinement and high Q-factor of the proposed structure give an opportunity to enhance the interaction between light and matter, which may have potential applications in nonlinear optics, optical sensors and surface enhanced Raman scattering.