Hu Shiqi, Chen Yaofei, Chen Yu, Chen Lei, Zheng Huadan, Azeman Nur Hidayah, Liu Ming Xian, Liu Gui-Shi, Luo Yunhan, Chen Zhe
Opt Express. 2020 Aug 17;28(17):25562-25573. doi: 10.1364/OE.397461.
Hyperbolic metamaterials (HMMs) have attracted increasing attentions because of their unique dispersion properties and the flexibility to control the dispersion by changing the components and fractions of the composed materials. In this work, for the first time, we demonstrate a plasmonic sensor based on a side-polished few-mode-fiber coated with a layered of HMM, which is composed of alternating layers of Ag and TiO. To optimize the sensor performance, the effects of the metal filling fraction (ρ) and the number of bilayers (N) on the HMM dispersion are thoroughly engineered with the effective medium theory and the finite element method. It is found that the HMM with ρ=0.7 and N = 3 can provide the average sensitivity of 5114.3 nm/RIU (RIU: refractive index unit), and the highest sensitivity 9000 nm/RIU in the surrounding refractive index (SRI) ranging from 1.33 to 1.40 RIU. The corresponding figure of merit (FOM) reaches a maximum of 230.8 RIU which is much higher than that of the conventional silver film based SPR sensor. The influence of ρ and N on the sensitivity are well explained from the aspects of the electrical field distribution and the dispersion relationship. This work opens a gate to significantly improve fiber plasmonic sensors performance by engineering the HMM dispersion, which is expected to meet the emergent demand in the biological, medical and clinical applications.
双曲线超材料（HMMs）因其独特的色散特性以及通过改变组成材料的成分和比例来控制色散的灵活性而受到越来越多的关注。在这项工作中，我们首次展示了一种基于侧面抛光的少模光纤的等离子体传感器，该光纤涂覆有一层由Ag和TiO交替层组成的HMM。为了优化传感器性能，利用有效介质理论和有限元方法深入研究了金属填充率（ρ）和双层数（N）对HMM色散的影响。结果发现，ρ = 0.7且N = 3的HMM在1.33至1.40 RIU的周围折射率（SRI）范围内可提供5114.3 nm/RIU（RIU：折射率单位）的平均灵敏度，最高灵敏度为9000 nm/RIU。相应的品质因数（FOM）最高可达230.8 RIU，远高于传统的基于银膜的表面等离子体共振（SPR）传感器。从电场分布和色散关系方面很好地解释了ρ和N对灵敏度的影响。这项工作为通过设计HMM色散来显著提高光纤等离子体传感器性能打开了一扇大门，有望满足生物、医学和临床应用中的迫切需求。
