基于MDM波导耦合方形复合腔的折射率传感研究  

Study of the Refractive Index Sensing based on MDM Waveguide Coupled with a Square-shaped Composite Resonant Cavity

作　　者：许蒲城 关建飞 XU Pucheng;GUAN Jianfei(College of Electronic and Optical Engineering&College of Flexible Electronics(Future Technology),Nanjing University of Posts and Telecommunications,Nanjing 210023,China)

机构地区：[1]南京邮电大学电子与光学工程学院、柔性电子(未来技术)学院,南京210023

出　　处：《光通信研究》2024年第6期55-61,共7页Study on Optical Communications

基　　金：国家自然科学基金资助项目(61775102,61905117);南京邮电大学科研启动资助项目(NY220050,NY214058)。

摘　　要：【目的】为了在纳米尺度下实现高灵敏度折射率传感器设计,文章提出了一种含支节的方形复合谐振腔侧向耦合金属-电介质-金属(MDM)型表面等离子激元(SPPs)波导的传感器结构。【方法】文章采用有限元法对比分析了引入支节腔前后方形谐振腔耦合MDM波导结构的透射峰谱线及谱峰位置模场分布的特点,揭示了引入支节腔后复合腔内一阶和二阶谐振模式的简并分离效应以及由此产生的具有非对称线型的四重Fano共振透射峰。通过改变谐振腔边长及支节长度等结构参数以及复合腔内填充媒质的折射率参数,计算出了透射谱线特征与谐振腔结构参数及媒质材料性质之间的依赖关系。【结果】通过分析结构参数对MDM波导透射谱峰中心波长的定量影响,文章阐明了透射谱峰波长所需满足的谐振条件以及支节腔对于不同谐振模式所具有的不同腔长增量。文章通过计算复合腔内不同填充介质对应的透射谱线,得到了谱峰中心波长随填充媒质折射率的改变呈现近似线性变化的规律,基于线性拟合结果计算出了四重Fano共振透射峰的传感灵敏度指标。【结论】计算结果表明,折射率传感灵敏度与复合腔有效腔长成正比,同时与谐振阶次成反比;当选取边长为360 nm且支节长度为210 nm的方形复合腔结构时,一阶Fano共振透射峰的传感灵敏度可达2000 nm/RIU。文章研究结果为高灵敏度折射率传感器的设计提供了有价值的参考。【Objective】In order to achieve a highly sensitive refractive index sensor in a nanoscale spatial dimension,a square composite resonant cavity containing a stub resonator has been proposed as a resonant element adjacent to Metal-Dielectric-Metal(MDM)Surface Plasmon Polaritons(SPPs)waveguide in this paper.【Methods】The paper employs the finite element method to comparatively analyze the characteristics of the transmission peak spectrum and the mode field distribution at the peak position of the square resonant cavity coupled MDM waveguide structure before and after the introduction of the stub cavity.The analysis results reveal that the degeneracy separation phenomenon of the first and second order quasi resonant modes in the composite cavity can be observed clearly when the stub resonator is added in the square-shaped cavity.Consequently,four transmission peaks with sharp edges have emerged in the transmission spectra,which are generated by the quadruple Fano resonance.By changing the structural parameters such as the side length of the square cavity and stub length,as well as the refractive index of the medium filled in the cavity,the dependence of the transmission spectra on the structural and material parameters of the resonant cavity was calculated in detail.【Results】By analyzing the quantitative impact of structural parameters on the peak wavelength,the resonance conditions responsible for the transmission peaks have been derived and the increments of the effective cavity length contributed by the stub resonator have been analyzed in turn for the four resonant modes.By calculating the transmission spectra associated with the varied medium filled in the composite cavity,the peak wavelength shows an approximate linear relationship with the refractive indexes of the filled medium.The sensing sensitivity of the quadruple transmission peaks has been obtained based on the linear fitting results.【Conclusion】The calculation results in the article indicate that the sensitivity of refractive index sensin

关 键 词：表面等离子激元 金属-电介质-金属波导 方形复合腔 Fano共振 折射率传感器 

分 类 号：TN256[电子电信—物理电子学]