| Metamaterials are artificially designed subwavelength structural materials with specific geometry,which break through the limitations of traditional materials and have many forms.The perfect absorber is the metamaterials amplitude modulator.A reasonable and orderly structural design of a material on the physical and geometric scale can achieve perfect absorption characteristics.The designed metal metamaterials can excite one or more plasmon resonance,and then manipulate and control the interaction between light and matter to achieve perfect absorption.The dielectric metamaterial based on anapole mode has become a good candidate for ultra-narrow band perfect absorption due to its low loss and nonradiative characteristics.This paper expounded the types and mechanism of surface plasmon resonance and summarized main structural types of plasmonic absorber.In addition,this paper discussed the excitation principle and application of anapole mode.Although these two resonant modes can concentrate electromagnetic fields on subwavelength regions and produce a high degree of local field enhancement,the inherent ohmic loss of metal makes it difficult to achieve the perfect absorption of ultra-narrow band.The dielectric with high refractive index can achieve narrow bandwidth and high-quality factor because it can excite the nonradiative anapole mode and its own low loss.Based on the above contents,two metamaterial absorbers were proposed based on different resonance modes:1.The single-and dual-gap ring plasmon nanostructure absorbers are designed and studied,respectively,and they can realize the absorption characteristics by exciting the gap plasmon resonance mode with sharp spectra.Compared with the single-gap ring nanostructure,the dual-gap ring nanostructure has the characteristics of double absorption channel,and the absorption intensity is better than the former.Therefore,they can be used as refractive index sensors,and the corresponding sensing sensitivity of the dual-gap ring plasmonic sensor is higher,which are 513nm/RIU and 809 nm/RIU with the refractive indices range of 1.32 to 1.37,respectively.Furthermore,the gap ring nanostructures are highly symmetrical,and have advantages in fabrication and pave the way for advanced optical devices to detect biomolecules.2.This paper is investigated a silicon-dielectric-metal nanostructure,possessing optical anapole mode in visible spectral range due to the destructive interference between electric and toroidal dipoles.Such the proposed nanostructure exhibits an ultra-narrow perfect absorption spectrum with the absorption bandwidth of 0.48 nm and the high-quality factor is 1763.Besides inherently low dissipative losses and strong anapole response,this optical nanostructure can demonstrate subtle refractive index sensing properties.Our work shed new light on active ultra-narrow band perfect absorption based on the optical anapole mode. |
