Multiple magnetic mode-based Fano resonance in split-ring resonator/disk nanocavities.
Plasmonic Fano resonance, enabled by the weak interaction between a bright super-radiant and a subradiant resonance mode, not only is fundamentally interesting, but also exhibits potential applications ranging from extraordinary optical transmission to biosensing. Here, we demonstrate strong Fano resonances in split-ring resonators/disk (SRR/D) nanocavities. The high-order magnetic modes are observed in SRRs by polarization-resolved transmission spectroscopy. When a disk is centered within the SRRs, multiple high-order magnetic modes are coupled to a broad electric dipole mode of SRR/D, leading to significant Fano resonance spectral features in near-IR regime. The strength and line shape of the Fano resonances are tuned through varying the SRR split-angle and interparticle distance between SRR and disk. Finite-difference-time-domain (FDTD) simulations are conducted to understand the coupling mechanism, and the results show good agreement with experimental data. Furthermore, the coupled structure gives a sensitivity of ∼282 nm/RIU with a figure of merit ∼4.
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371.
Qing
Q
Zhang
Xinglin
X
Wen
Guangyuan
G
Li
Qifeng
Q
Ruan
Jianfang
J
Wang
Qihua
Q
Xiong
D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D003198:Computer Simulation; D008027:Light; D060328:Magnetic Phenomena; D008280:Magnetics; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry*; D055095:Optics and Photonics; D012031:Refractometry; D013053:Spectrophotometry; D013059:Spectrum Analysis, Raman / Q000379:methods*; D020349:Surface Plasmon Resonance