Optical Sensing Technology Based On Silicon-based Metasurface

All-dielectric metasurface has a broad prospect in applications due to its advantage of low loss.And silicon is often used in all-dielectric metasurface because of its high refractive index and low loss in near-infrared range.Compared with the surface plasmon resonance(SPR)metasurface which only exists electric resonance,the silicon-based all-dielectric metasurface can sitimulate both electric resonance and magnetic resonance,and the position of electromagnetic resonance can be controlled by adjusting the structural parameters of the metasurface,which has a greater prospect in practical applicationIn this paper,several silicon metasurface sensors and their practical applications are introduced.When the incident light field is irradiated perpendically to the metasurface,the electric and magnetic resonance with small quality factor can appear.Design shape and parameters of the metasurface structure carefully,the Fano resonance and bound states in the continuum resonance with large quality factor can be realized.The tolerance of fabrication is larger when electric resonance or magnetic resonance is generated,,so the resonance peak can easier to realize.However,Fano resonance and bound states in continuum resonance are difficult to realize in practical application because of their harsh conditions and high requirements for fabrication.Using finite difference time domain simulation software to find out the structure parameters of metasurface whose magnetic resonance,electric resonance or electromagnetic resonance located in the near infrared range.By analyzing the mode field of each transmission peak,the resonance type of transmission peak can be determined.After that,the designed silicon metasurface was prepared by coating,homogenizing,electron beam exposure,developing,ion beam etching and adhesive removal.Then,disc and elliptical silicon based metasurface optical sensing technology are verified.Disc shaped metasurface combined with microfluidic channels implements the refractive index sensing:liquid with different refractive indexes is pumped into the microfluidic channels by liquid pump,the changes of transmission peak are detected by self-built optical path.The sensing sensitivity of magnetic resonance refractive index sensing and electric resonance refractive index sensing are 230nm/RIU and 320nm/RIU,respectively.Refractive index sensing technology plays an important role in detecting impurity in food and water pollution.On this basis,the biomolecule measurement utilizing metasurface is also realized by chemical bond coupling method and specific adsorption between biomolecules.Firstly,the chemical bond of biotin-Streptavidin pair is used to capture Streptavidin.The qualitative and quantitative analysis of the biotin-Streptavidin pair shows that the detection limit of the metasurface of the disc structure was 10-12mol/L,which is 4 orders higher than that of the traditional SPR metasurface detection of streptavidin.After that,elliptical metasurface is used to test the Streptavidin,the limitation is 10-13 mol/L,which is an order of magnitude higher than that of the disk structure and 5 orders higher than that of the traditional SPR metasurface detection of streptavidin.Then the quantitative and qualitative exploration of acetylcholinesterase(AChE)antigen was carried out by using the elliptical structure silicon metasurface.The specific adsorption between AChE antigen and antibody is used to capture the antigen,and the limit detection concentration of AChE antigen is 0.001mg/mL after the metasurface is blown dry,which is an order of magnitude higher than that of the traditional SPR metasurface detection.This is mainly due to SPR metasurface tend to generate strong loss while resonant,such loss can generate heat effect to damage the bioactivity of biological molecules,and the silicon-based metasurface only generate extremely low loss while resonant,and have no effect on the bioactivity of biological molecules.Metasurface based on silicon biomolecule sensing have the advantages of low preparation cost,convenient operation and high detection accuracy,which can play a great role in medical diagnosis and environmental monitoring.