Fano Interference Between Higher Localized and Propagating Surface Plasmon Modes in Nanovoid Arrays

Abstract

Surface plasmon resonance-based optical properties for gold nanovoid arrays were analyzed using threedimensional finite-difference time-domain method, revealing that two asymmetric Fano resonances, with extremely low reflectivity and narrow line width, are caused by the strong interference between localized quadrupolar and hexadecapolar modes and propagating surface plasmon mode. The two Fano resonances produce significant electromagnetic field enhancement, resulting in 7 orders of magnitude surface-enhanced Raman scattering (SERS) enhancement, with about 100 times more than that produced by single propagating surface plasmon polaritons (SPPs) or localized surface plasmon resonance (LSPR) mode, including dipolar mode. Their narrow line width and giant field strength also allow highly sensitive sensing of refractive index; the sensitivities and figure of merits for such Fano resonance-based sensor are predicted to be 789 and 642 nm/RIU, 39 and 31, respectively. These plasmonic characteristics, thus, would enable the nanovoid arrays for using in wide practical applications including surface-enhanced spectroscopy and surface plasmon sensor.

Electroless deposition of Ag through-void arrays for integrated extraordinary optical transmission-based plasmonic sensing and surface-enhanced Raman scattering

“…According to this equation, the (1, 0) SPP mode for the through-SSV array with P = 275 nm is beyond spectrometer's spectral wavelength available, while they should appear at 464 and 560 nm for the arrays with P = 413 and P = 616 nm, respectively. In addition to the SPP mode, the other two dominant peaks shown in Figure 3B are ascribed to the localized dipole mode and quadrupolar mode, respectively [34]. The sharp transmission peak, whose wavelength is shorter than that of the SPP peak, was tentatively ascribed to the hexadecapolar mode [34].…”

“…In addition to the SPP mode, the other two dominant peaks shown in Figure 3B are ascribed to the localized dipole mode and quadrupolar mode, respectively [34]. The sharp transmission peak, whose wavelength is shorter than that of the SPP peak, was tentatively ascribed to the hexadecapolar mode [34]. The appearance of localized plasmons is because the Ag through-SSV arrays also own structure characteristics for single, isolated nanostructures.…”

High Figure of Merit (FOM) of Bragg Modes in Au‐Coated Nanodisk Arrays for Plasmonic Sensing

“…Structures supporting a SPP are generally on the order of FOM = 23 to 39, which includes the FOM of a thin Au film classically used in SPR sensing (FOM = 25 to 39) . Significantly higher FOM can be achieved with SPP with Fano resonances, where the FOM ranges from 39 and 252, and often exploits subwavelength nanostructures such as the nanoslits structures, grating structures, suspended nanohole arrays, or nanomushrooms to reach higher FOM. A more extensive list of FOM for a series of nanostructures was provided elsewhere for comparison purposes .…”

Optical Refractive Index Sensors with Plasmonic and Photonic Structures: Promising and Inconvenient Truth

“…is not equivalent to "coupling". Upon resonance, the coupling of LSP and PSP will sometimes give rise to hybridized plasmonic modes [66,[688][689][690][691], such as Fano resonance, which has been covered in previous section.…”