| As an important branch in the field of biosensor,optical biosensor based on the spectral information of samples with different refractive index realizes the dynamic information detection of biomolecule concentration and composition,and has the advantages of low optical loss and high detection sensitivity.Among them,the design of all dielectric photonic crystal structure,the local mode of Bloch surface wave in defect layer and the regulation of optical sensing performance have become the research hotspot in the field of optical biosensor.In this paper,a new idea for constructing Bloch surface wave(BSW)using Ag nanoparticles(AgNPs)or two-dimensional hole-array grating is proposed for the all-dielectric photonic crystal structure and its optical biosensing performance based on Rsoft optical simulation software.The main research contents and innovations of this paper are as follows:(1)Based on the theory of BSW resonance and the optical properties of semi-infinite one-dimensional photonic crystal,the sensing model of porous silicon photonic crystal is constructed,and the formation mechanism of BSW is studied systematically.The influence of the period number of the photonic crystal,metal particle material and the thickness of the defect layer on the quality factor of the resonance peak of the reflection spectrum is calculated by the Rigorous Coupled Wave Analysis method.Based on the azimuthal interrogation method,four different models of analyte adhesion/penetration are established for the change of refractive index in a specific region,and their sensing characteristics are analyzed.The results show that the sharpness of the resonant dip peak increases first and then decreases with the increase of the period number of the photonic crystal,and the best quality factor is obtained when the period number is 8.Compared with metal nanoparticles such as gold,aluminum and copper,AgNPs has better BSW coupling ability.Among them,the wavelength sensitivity of prism excitation configuration is as high as 1752 nm/RIU;the angle sensitivity of AgNPs excitation BSW is as high as 703°/RIU.(2)A novel optical biosensor based on porous Si3N4/SiO2 bi-layer asymmetric photonic crystal(square lattice)slab is proposed.Based on the spectral analysis method,the influence of parameters such as the lattice constant and the thickness of photonic crystal slab on its sensing performance(quality factor)is studied,and the detection of the concentration and filling rate of glycerin is realized.The results show that when the TTT lattice constant is 800 nm,the reflection resonance peak can obtain a symmetrical Lorentz line;the theoretical sensitivity of the structure is as high as 286 nm/RIU in the wavelength range of 1400 nm to 1600 nm,which effectively reduces the manufacturing difficulty of traditional single-layer photonic crystal slab and eliminates the surface stress under symmetrical structure(3)A two-dimensional hole-array grating coupled BSW model is constructed,and the effects of photonic crystal period,the radius of hole,the thickness of grating layer and dielectric loss on the resonance characteristics of BSW are studied.Combined with the dispersion curve and field distribution characteristics,the influence law of Bloch surface state is explored,and the theoretical design method of two-dimensional hole-array grating coupled BSW optical biosensor is formed.The results show that BSW is excited on the surface of the two-dimensional hole-array grating layer or the interface between the Bragg mirror and the biological solution;compared with the traditional polarization angle coupling mode,the BSW generated by the azimuth greatly enhances the angle sensitivity(up to 2255°/RIU);at the same time,BSW coupling regulation can be realized by rotating polar angle and azimuthal angle. |
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