传感品质因数增强的塔姆-表面等离激元杂化模式

Tamm-surface plasmon hybrid mode for improving sensing figure of merit

基于棱镜耦合的金膜表面塔姆等离激元(Tamm plasmon polarition,TPP)与表面等离极化激元(surface plasmon polariton,SPP)的杂化耦合受到广泛的关注和研究,但这种传统的激发装置由于拥有体积庞大的棱镜等光学元件以及对入射光角度精准控制有严格要求,限制了其集成化发展和实际应用。为了简化TPP和SPP杂化耦合激发方式,本文提出了一种光栅耦合型多层堆叠结构设计。该结构主要包括三部分:顶部纳米厚度的金膜、中间一维布拉格光子晶体以及底部金纳米光栅。在该结构中利用底部纳米光栅的一级透射光同时实现了顶部金膜上下表面SPP和TPP共振激发。两种模式之间的耦合杂化作用极大地减少了模式的共振带宽,从而使TPP-SPP模式的传感品质因数得到了显著的提高。此外,通过改变纳米光栅的周期和组成一维布拉格光子晶体的介质层厚度,SPP和TPP可以在较宽光谱范围内实现耦合杂化。相比于传统棱镜式的TPP和SPP双模式耦合结构,设计的光栅耦合型的多层堆叠结构无需借助棱镜和对入射角精确调控,在正入射光照射下就可实现两种模式的共振耦合,这不仅易于结构的进一步集成和小型化,同时对拓宽表面等离激元传感器的实际应用具有重要的意义。

The hybrid coupling of Tamm plasmon polariton(TPP)and surface plasmon polariton(SPP)on the surface of a gold film based on the prism coupling has attracted extensive attention and has been widely investigated.However,the traditional excitation configuration has bulky optical elements and requires accurate control of the angle of incident light,which limits its integration and practical application.In order to simplify the excitation condition of the TPP-SPP hybrid mode,a feasible grating-coupled multilayer stack structure is proposed in this paper.The structure mainly consists of three parts:a nanometric thin gold film on the top layer,a onedimensional Bragg photonic crystal in the middle,and a gold nanograting on the bottom.In this structure,the SPR and TPP resonance excitations on the upper and lower surfaces of the top gold film are simultaneously achieved by utilizing the first-order transmitted light of the bottom nanograting.The hybrid coupling between the two modes greatly reduces the resonance bandwidth of the generated mode,thereby significantly improving the sensing figure of merit of the generated mode.Additionally,the hybrid coupling of both SPP and TPP modes can be realized in a wide spectral range by altering the period of the nanograting and the thickness of the one-dimensional Bragg photonic crystal.Compared with the traditional prism-coupled TPP and SPP dual-mode coupling structures,the designed grating-coupled multilayer nanostructure can realize the resonant coupling of the two modes at the normal incidence without prism and limitation of incident angle.This not only facilitates the further integration and miniaturization of the structure,but also has important significance for broadening the practical application of surface plasmon resonance sensors.