Improved strong field enhancement and ultranarrow perfect absorption based on anapole mode in slotted Si nanodisk metamaterial

Abstract

Compared with the plasmon resonance suppressed by ohmic loss, high refractive index dielectric metamaterials have become a new frontier of nanophotonics because of their small loss. In this work, we numerically simulate the structures of Si and slotted Si nanodisk with the SiO2 substrate, and slotted Si nanodisk with the Ag substrate. The slotted Si nanodisk excited with anapole mode reveals strong near field enhancement about 70 times in slotted gap regions. When the slotted Si nanodisk deposited on Ag substrate separated by SiO2 layer, the designed structure shows the ultranarrow perfect absorption with the line width of 1.38 nm and the quality factor of 602, and the corresponding electric field enhancement in the Si nanodisk increases to 125. Our work provides a new idea for electric field enhancement and ultranarrow perfect absorption based on manipulation of anapole mode in dielectric metamaterials, and provides potential applications in optical sensors, nonlinear optics and surface enhanced Raman scattering.