| Optical micro-nano structures have a wide range of application prospects in the field of sensing due to their diverse structure types and superior sensing performance.Since surface plasmon resonance was first reported in 1902,many scholars at home and abroad have aroused strong research interest.In recent years,more and more sensor structures based on surface plasmon resonance and waveguide resonance have been designed at home and abroad.It has also made rapid progress in theory and application research and made great breakthroughs in the improvement of sensing performance.However,there are few pieces of research on the coupling theory research of various basic structures,the analysis of the evolution law of spectral characteristics,electromagnetic field enhancement,the use of high-performance two-dimensional materials,and the optimization design of structural parameters.Therefore,this paper mainly focuses on the design of composite micro-nano structures composed of basic structures.The coupling effect of optical characteristics between structures and the realization of electromagnetic field enhancement to improve the sensing performance were explored,aiming at the design and optimization of multiple Fano sensing structures and further expanding the detection range of samples to be tested.The main research work of this paper includes:Firstly,based on the theory of surface plasmon resonance and mode coupling,a composite micro-nano structure based on surface plasmon coupled waveguide doped with new materials was designed.The upper structure and lower waveguide structure combined by prism and Au film were simulated by COMSOL software to generate wide and narrow discrete states respectively.The near-field coupling occurred between the two structures,thus forming Fano resonances.The sensor structure is numerically simulated and analyzed.The energy transmission characteristics of surface plasmons and the formation and evolution mechanism of double Fano resonance at different incident angles of a certain wavelength are analyzed and introduced by using the reflection Angle spectrum.The different spectral response curves of TE and TM modes are described respectively.The influence of the structural parameters of the surface plasmon-coupled waveguide on the Fano resonance spectral response curve was analyzed,to optimize the structural model and realize the high-precision detection of solution concentration,which laid a theoretical foundation for the optimization of structural parameters and the proposal of the all-dielectric Fano resonance sensing structure.Secondly,an all-dielectric material sensor with high FOM value based on Mo S2thin-film coupled waveguide is designed.Due to the existence of ohm loss in metal materials,the performance of the sensor is affected to some extent.Based on the waveguide coupled surface plasmon resonance sensor structure,Mo S2 material is introduced,and an all-dielectric material Mo S2 thin-film coupled waveguide structure sensor is proposed.The wide resonance in the low-quality factor waveguide with a wider frequency domain is generated,and the narrow resonance in the high-quality factor waveguide with a narrower frequency domain is generated.The sensor structure was numerically simulated and analyzed.Combined with the reflection Angle spectrum,the Fano resonance generated by the coupling between the two waveguide modes was further described and verified.The influence of Mo S2 layers and various structural parameters on the sensing performance was explored.Finally,the structure parameters based on the optical sensing design have a great influence on the resonance performance of Fano.The parameters of the surface plasma-coupled waveguide structure and the Mo S2 thin-film coupled waveguide structure were respectively optimized by the optimization algorithm.First,for the surface plasma-coupled waveguide structure,the two spectral performance indexes of the FOM value and the sensitivity of the double Fano resonance were selected as the optimization objectives,and three structural parameters with great influence on the spectrum were selected.Using BP neural network to establish the mathematical relationship between the structural parameters and the performance index,and then using Particle swarm optimization（PSO）to find the structural parameter set when the FOM value and sensitivity of double Fano resonance reach the optimal.The optimization of micro-nano structure parameters is realized in the global scope.Secondly,based on the Mo S2-coupled waveguide structure,with the double waveguide layer thickness,the thickness of two adjacent dielectric layers,and the number of Mo S2 layers as input parameters,and the FOM value as output parameters,the data set was input into the deep extreme learning machine（DELM）model.An optimization algorithm based on a deep extreme learning machine was established,the weight parameters were optimized by the optimization algorithm,and the spectral optimization ability of different optimization algorithms was compared.Finally,the prediction model of GWO-DELM was established to obtain a better spectral response,and the sensing performance was greatly improved. |
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