Tunable Subradiant Mode in Free-Standing Metallic Nanohole Arrays for High-Performance Plasmofluidic Sensing

Abstract

Free-standing metallic nanohole arrays (NAs) exhibit extraordinary benefits in combining nanofluidics and plasmonics in a single platform for flow-through plasmofluidic sensing. However, the sensing performance of NAs is usually limited by the low quality factor of the transmission peak, resulting from strong radiative damping. Here, we demonstrate a concept for high-performance plasmofluidic sensing based on the subradiant mode in free-standing metallic NAs. We show that the subradiant mode exhibits a good spectral resolution only when the dielectric media at the upper and lower metal surfaces are symmetric; otherwise, it easily emerges into other features present in the same spectral region. Therefore, free-standing NAs are particularly suitable for highly sensitive microfluidic sensing based on the subradiant mode. In addition, the subradiant mode exhibits a highly tunable frequency and refractive index sensitivity (RIS), depending strongly on the film thickness and periodicity and weakly on the hole radius. Compared with the superradiant mode, the subradiant mode exhibits a much narrower spectral characteristic and more intensely enhanced electric fields at metal surfaces with larger field extension and longer lifetime. The high RIS and good quality factor together afford the subradiant mode a much better sensing performance than the superradiant one. This work is significant for developing high-performance lab-on-a-chip devices.

Hydrogen‐Doping‐Induced Metal‐Like Ultrahigh Free‐Carrier Concentration in Metal‐Oxide Material for Giant and Tunable Plasmon Resonance

“…The HMO-4 sample exhibits the strongest plasmonic signal peak at 559 nm. Compared with the shift of LSPR peak caused by alloying or morphological changes in noble metals, [27,28] the quasi-metallic H x MoO 3 samples with different hydrogenation levels also exhibit similar phenomena. It is worth noting that the plasmonic wavelength can be finely tuned by varying the H-doping level, as reflected by the PB peaks of HMO-1, HMO-2, HMO-3, and HMO-4 at around 636, 610, 578, and 559 nm, respectively.…”

Plasmonic Nanohole Arrays on Top of Porous Silicon Sensors: A Win–Win Situation

“…Plasmonic nanohole arrays on top of PSi monolayers had a sensitivity of 386 ± 5 nm/RIU, whereas sensors prepared on glass substrates had sensitivities of 213 ± 12 nm/RIU. The higher sensitivity of the hybrid sensors might be based on the larger accessible surface area for sensing (PSi vs solid glass). , …”

“…In the latter case, not only the refractive index of the supporting material dictates the optical signature of the sensor but the supporting material also defines the accessible surface area for capturing and detecting target analytes. Consequently, plasmonic nanohole arrays were not only fabricated on top of solid substrates but also combined with porous inorganic materials and polymers , or even investigated as free-standing sensors . Using another optical sensor platform as a support for plasmonic nanohole arrays in order to provide a second sensing channel has not been published until now, to the best of our knowledge.…”

Investigation of Surface Plasmon Polaritons based Gas sensor: Far and Near field Analysis

“…Extraordinary optical transmission (EOT) based sensors are mostly composed of cylindrical holes in metal. Holes in metal are ribbed periodically which boost the sensitivity when the field interacts with the analyte [21].…”