Design Of Optical Anapole Mode-enhanced Refractive Index Sensor

Sensing technology based on detecting refractive index changes has been widely used in biosensing and other fields.In this paper,the principle of refractive index change detection is studied,and the plasmon nanopore sensing module is designed to optimize the structural form and select the structural parameters to improve the refractive index detection sensitivity.Combining the advantages of optical plasmon and nanopore technology,bow-tie plasmon nanostructures based on gold films are designed to enhance the interaction between light and nanopore structures,improve the field enhancement factor and improve the detection sensitivity of nanoparticles.In order to further overcome the manufacturing process problems of bow-tie structure,a metal film double nanopore structure is designed,which uses the intersection of double nanopores to form a tip structure instead of bow-tie tip structure,and further improves the local restricted distribution of field and the particle capture efficiency of nanopores.Secondly,aiming at the defect of particle ring breaking caused by heat generated by the absorption of light waves by plasmon nanostructures,a metal-dielectric nanostructure array based on anapole mode is designed,which can minimize the energy loss caused by plasmon nanostructures,achieve greater field enhancement and higher sensitivity,and reduce particle ring breaking caused by photothermal conversion.Finally,based on the high refractive index sensitivity structure,the groove structure is designed to realize single particle capture,which further improves the particle capture efficiency.The thesis uses the finite difference time domain method(FDTD)to simulate and analyze different structures.The results show that the maximum electric field enhancement factor is more than 120 when the plasmon is combined with nanopore,which provides 2.5times additional electric field enhancement factor compared with the traditional solid nanopore enhancement factor 48.In addition,the resonance peak shift of the designed nanostructure based on anapole mode is sensitive to the medium whose refractive index changes between 1.30 and 1.39.At a resonance wavelength of 800 nm,the sensitivity reaches589 nm/RIU.Compared with the solid disk,the structure with nano-slits has an electric field enhancement factor of more than three orders of magnitude.Single particle can be sensitive to the change of light intensity through the optical detector,which realizes the detection of refractive index change of single particle and improves the capture efficiency of particles.The innovation of this paper lies in the combination of plasmon and optical anapole mode,which can effectively reduce the light absorption and improve the refractive index sensitivity of the structure.The research in this paper lays a theoretical foundation and technical reference for structure design for single molecule detection in solution.