China CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
Nanoscale. 2017 Oct 12;9(39):14998-15004. doi: 10.1039/c7nr05919a.
Plasmonic Fano metamaterials provide a unique platform for optical sensing applications due to their sharp spectral response and the ability to confine light to nanoscale regions that make them a strong prospect for refractive-index sensing. Higher order Fano resonance modes in noble metal plasmonic structures can further improve the sensitivity, but their applications are heavily limited by crosstalk between different modes due to the large damping rates and broadband spectral responses of the metal plasmon modes. Here, we create pure higher order Fano modes by designing asymmetric metamaterials comprised of a split-ring resonator and disk with a low-loss graphene plasmon. These higher order modes are highly sensitive to the nanoscale analyte (8 nm thick) both in refractive-index and in infrared vibrational fingerprint sensing, as demonstrated by the numerical calculation. The frequency sensitivity and figure-of-merit of the hexacontatetrapolar mode can reach 289 cm per RIU and 29, respectively, and it can probe the weak infrared vibrational modes of the analyte with more than 400 times enhancement. The enhanced sensitivity and tunability of higher order Fano graphene metamaterials promise a high-performance nanoscale optical sensor.
等离子体 Fano 超材料由于其光谱响应尖锐和将光限制在纳米区域的能力，为光学传感应用提供了独特的平台，这使它们成为折射率传感的有力候选者。贵金属等离子体结构中的高阶 Fano 共振模式可以进一步提高灵敏度，但由于金属等离子体模式的大阻尼率和宽带光谱响应，不同模式之间的串扰严重限制了它们的应用。在这里，我们通过设计由分环谐振器和盘组成的不对称超材料来产生纯高阶 Fano 模式，该超材料具有低损耗的石墨烯等离子体。数值计算表明，这些高阶模式对纳米级分析物（8nm 厚）在折射率和红外振动指纹传感方面都具有高度的敏感性。六重四极模式的频率灵敏度和品质因数可以分别达到 289cm/RIU 和 29，并且可以对分析物的弱红外振动模式进行超过 400 倍的增强探测。高阶 Fano 石墨烯超材料的增强灵敏度和可调谐性有望实现高性能纳米级光学传感器。
