Research And Application Of All-dielectric Metasurface Based On Continuous Domain Bound Stat

Metasurfaces,a kind of artificial material with sub-wavelength thickness,has remarkable performance in the manipulation of electromagnetic waves,and can regulate the phase,amplitude and polarization state of electromagnetic waves.Compared with 3D metamaterials,it has the advantages of miniaturization and easy integration.All-dielectric metasurfaces,which can excite high Q-factor resonance and enhance near-field coupling owing to the low inherent resistive losses and high laser damage threshold,have been widely proposed recently.Additionally,recent studies have revealed bound state in the continuum（BIC）,which provides a new way to realize high Q factor and strong near-field enhancement.The resonance of quasi-BICs generated at the all-dielectric metasurface has a very high Q-factor,which provides a new way to enhance light-matter interactions such as improving refractive index sensitivity and enhancing Goos-Hanchen shift.In this paper,the all-dielectric metasurfaces based on the bound state in the continuum are studied.The refractive index sensing and enhancing Goos-Hanchen shift application of high-Q resonances supported by the symmetry-protected BIC theory is investigated,respectively.The main work are as follows:1.The research significance and application prospect of the metasurfaces are introduced briefly.The electromagnetic radiation characteristics of resonant mode in all-dielectric metasurface are introduced in detail.Finally,the development process and physical mechanisms of the BIC is introduced.2.A kind of all-dielectric metasurface based on toroidal dipole bound states in the continuum is proposed.It can be used measure the refractive index and temperature.The physical mechanism of the resonance corresponding to the metasurfaces is analyzed by calculating the far-field scattered power and plotting the magnetic field distribution.The relationship between the asymmetric parameters and the Q-factor,indicates that the resonance at short wavelengths corresponds to the toroidal dipole（TD）resonance governed by the symmetry-protected bound states in the continuum（BIC）.Influences of the incident angles and geometric parameters on the resonant modes are also discussed.High Q-factor of the TD quasi-BIC makes the designed metasurfaces to be a promising sensor.The sensitivity and figure of merit（FOM）for refractive index sensing are 746nm/RIU and 18650RIU^-1,respectively.For temperature sensing,the sensitivity can be as high as 54 pm/℃.This study provides a new approach for the excitation of strong TD quasi-BIC resonance,and facilitates the design of refractive index sensing.3.Based on the magnetic quadrupole bound states in the continuum,an all-dielectric metasurface gas sensor is designed for the near-infrared band.The resonance of the designed metasurface is proved to belong to the symmetry-protected BIC by calculating the relationship between the asymmetric parameters and the Q-factor.Influences of the incident condition and geometric parameters on the resonant modes are also discussed,and the application in communication field is extended.Refractive index sensitivity analysis showed that the sensitivity（S）and FOM can be up to 450 nm/RIU,7500 RIU^-1.Therefore,the designed all-dielectric metasurface has a potential application in gas sensors and communication band filters.4.An all-dielectric metasurface based on magnetic dipole bound states in the continuum is designed,and two methods for modulating the BIC in the all-dielectric metasurface are proposed.The oblique incidence method provides a new way to enhance the Goos-Hanchen shift.The quasi-BIC resonance can enhance the GH displacement while the reflectance reaches 100%,which makes it easy to detect.Based on this,an ultrasensitive ambient refractive index sensor based on quasi-BIC enhanced Goos-H（?）nchen shift is theoretically designed.