Research On Characteristics And Applications Of Multiple Fano Resonances Based On All-dielectric Metasurface

The further development of optical applications is fundamentally limited due to the limited types of atoms and lattice arrangement of materials that exist naturally.Metamaterials emerge as The Times require.The properties of metamaterials are not only related to the chemical composition of the material itself,but also determined by the microstructural units that comprise it.By adjusting the structure of metamaterials,any equivalent dielectric constant and permeability can be realized in principle,including the realization of negative refractive index.Considering the complexity of structure preparation,function tuning and system integration,the superstructural materials have been developing towards the direction of low loss,ultra-thin,adjustable and easy to integrate,and have undergone a gradual transformation from threedimensional body structure to two-dimensional metasurface structure.This paper explores its potential in sensor,slow-light and optical switching applications based on all-dielectric metasurface.The main research results are as follows:(1)Firstly,a Si all-dielectric metasurface with a custom pentagonal etched-hole is presented.By adjusting the asymmetric parameters,two Fano peaks matching the BIC mechanism of symmetric protection are successfully excited,and the TD mode is supported.The calculation results show that the sensor performance is high,and the sensitivity is up to 240nm/RIU.The highest FOM value is 700 RIU-1.Then,based on the pentagonal etched hole scheme,the pentagonal was changed into a semicircle.The results showed that the Anapole mode was excited in the far field,which came from the destructive interference of TD and ED,reduced the radiation loss,and further strengthened the local field capability.The sensitivity and FOM values are 277.5nm/RIU and 1387.5 RIU-1,respectively.(2)The slow light application of multilayer all-dielectric metasurface is studied.Firstly,the single-layer metasurface structure is presented,and its near-field electromagnetic field distribution and sensing performance are analyzed.It is found that the electromagnetic fields at the four Fano peak wavelengths are mainly distributed in the gaps of the structure,which brings excellent sensing performance to the metasurface.The sensitivity of the four Fano peaks is calculated to be up to 365nm/RIU.Then,a layer of Si is added to the single-layer metasurface structure,and the enhancement effect of the introduction of the new Si layer on the electric field is analyzed.It is found that the maximum electric field enhancement of the multi-layer metasurface is 154 times,which is more than twice that of the single-layer metasurface.Therefore,the multilayer metasurface has a significant enhancement effect on the electric field,and the resulting enhancement of the electromagnetic field can enhance the nonlinear response,such as Raman reflection,energy guidance and harmonic generation.Finally,the slow light characteristics of EIT-like are analyzed,and the calculated group delay is 3.22ps,which has a good potential for slow light application.Multiple Fano excited at the same time show different behaviors to the change of polarization Angle,with four peaks turned on,three peaks turned off,and some peaks showing polarization independent characteristics,so the proposed structure can also be applied to the bidirectional optical switch.The metasurface structure designed in this paper provides inspiration for the application of all-dielectric metasurface in the fields of sensor,slow light,optical switch,and so on.Moreover,the structure of multi-layer metasurface is innovated,which has guiding significance for the study of all-dielectric metasurface.