金纳米锥阵列与金薄膜耦合结构表面等离子体折射率传感研究

Research on surface plasmon refractive index sensing of gold nano cone array and gold film coupling structure

设计了基于SiO_(2)薄膜间隔的金纳米锥与金薄膜耦合结构表面等离子体共振折射率传感器。使用时域有限差分法研究了复合结构中的表面等离子体共振模式,复合结构不仅能够激发局域表面等离子体共振,也可激发传播表面等离子体共振。入射电磁波的能量部分通过单个金纳米锥耦合到局域表面等离子体,部分通过金纳米锥阵列二维光栅耦合到传播表面等离子体。在待测物折射率1.30~1.40的范围内,对复合结构的反射光谱进行了模拟研究,发现共振波长与分析物折射率呈线性关系,且由于局域和传播表面等离子体的高效激发,反射光谱共振峰处的反射率几乎为零。此外,在最优的金纳米锥几何参数下,传播表面等离子体共振模式的半高全宽非常窄,灵敏度和品质因数分别达到770 nm/RIU和113 RIU^(-1),具有良好的折射率传感性能。所设计的复合结构作为表面等离子体共振传感器有望广泛应用于生物检测领域。

A surface plasmon resonance refractive index sensor based on the coupling structure of gold nano cones and a gold film with a SiO_(2)film as spacer-layer is designed.The surface plasmon resonance modes in the composite structure are studied by using the Finite Difference Time Domain method.The composite structure can stimulate not only localized surface plasmon,but also propagating surface plasmon.The energy of the incident electromagnetic wave is partially coupled to the localized surface plasmon through a single gold nano cone,and partially coupled to the propagating surface plasmon through a grating of gold nano cone array.The reflection spectra of the composite structure are simulated in the refractive index range of 1.30 to 1.40.It is found that the resonance wavelength has a linear relationship with the refractive index of the analyte,and the reflectivity at the resonance is almost zero due to the strong resonance coupling between localized and propagating surface plasmon.In addition,the full width at half maximum of propagating surface plasmon resonance mode is very narrow when the geometric parameters of gold nano cone are optimized.The sensitivity and figure of merit reach770 nm/RIU and 113 RIU^(-1) respectively,and it has good refractive index sensing performance.The designed composite structure is expected to be widely used in the field of biochemical detection.