Study On Fano Resonance Sensing Properties Based On All-Dielectric Metasurfaces

In recent years,metasurfaces have been widely used in the field of optical micronano sensing due to their unique electromagnetic properties of small size,easy fabrication,and on-chip integration.Significant near-field enhancement can be achieved by exciting special physical phenomena such as Fano resonance by using metasurface structures of metallic or dielectric materials,thereby designing optical refractive index sensing devices with high performance.Plasmonic metasurfaces contained metal have limited applications in nanophotonics due to their high ohmic losses in the visible and near-infrared range,and all-dielectric metasurfaces can overcome this shortcoming by virtue of their material properties,exhibiting better sensing performance.In this thesis,based on the physical properties of all-dielectric metasurfaces and the formation mechanism of Fano resonance,several different Fano resonance sensing structures based on all-dielectric metasurfaces are designed.The resonance mechanism and sensing characteristics of the structure are deeply analyzed to realize design refinement and performance optimization of alldielectric metasurface sensing structures.The research contents of the paper mainly include:First,based on the Mie resonance theory,the characteristics of basic electromagnetic sources,and the theory of multipole interferences of dielectric metasurfaces,an alldielectric metasurface with a semi-circle/semi-disk dimer structure is designed.The transmission characteristics of the structure and the formation mechanism of Fano resonance are analyzed by simulation,and the effects of various structural parameters and the polarization angle of incident light on the Fano characteristics are discussed.Through the optimization of structural parameters,the sensing performance of the structure is further analyzed,which provides a basis for the research of Fano resonance sensing structure based on all-dielectric metasurfaces.Secondly,a sensing device based on a monomeric metasurface of silicon notched disks and integrated microfluidic channels is designed.The double high-Q Fano resonances is excited by the introduction of a notch and its generation mechanism is analyzed.The influence of various structural parameters on the transmission characteristics is discussed,and it is found that the structure can realize the independent tuning of double Fano resonances and the simultaneous tuning of multiple resonances.The influence of the thickness of the test object in the microfluidic channel on the resonance peak is analyzed,and the sensing performance of the structure is obtained.In addition,the resonance characteristics and sensing performance of the silicon disk structure with different numbers of notches are also discussed,and finally the structure improvement and performance improvement are realized.Finally,a composite structure of an all-dielectric metasurface coupled waveguide layer based on a silicon notched disk is designed,and a new way of exciting Fano resonance is realized by introducing the waveguide layer.The properties of the multiple Fano resonances obtained in the two polarization modes are discussed and the mechanism of their generation is explained.In addition,by analyzing the influence of various structural parameters on the transmission spectrum under y-polarization,the structure is optimized and the sensing performance is improved.The proposed structure provides a new idea for the design of sensing structures that excite multiple Fano resonances.