Interfering Plasmons in Coupled Nanoresonators to Boost Light Localization and SERS

Abstract

Plasmonic self-assembled nanocavities are ideal platforms for extreme light localization as they deliver mode volumes of <50 nm 3 . Here we show that high-order plasmonic modes within additional micrometer-scale resonators surrounding each nanocavity can boost light localization to intensity enhancements >10 5 . Plasmon interference in these hybrid microresonator nanocavities produces surface-enhanced Raman scattering (SERS) signals many-fold larger than in the bare plasmonic constructs. These now allow remote access to molecules inside the ultrathin gaps, avoiding direct irradiation and thus preventing molecular damage. Combining subnanometer gaps with micrometer-scale resonators places a high computational demand on simulations, so a generalized boundary element method (BEM) solver is developed which requires 100-fold less computational resources to characterize these systems. Our results on extreme near-field enhancement open new potential for single-molecule photonic circuits, mid-infrared detectors, and remote spectroscopy.

Trends in Nanophotonics‐Enabled Optofluidic Biosensors

“…Nanophotonics enables the efficient localization of light into nanoscale volumes comparable in size to many relevant biomolecules, strongly enhancing the light-matter interactions and transducing the molecular binding events into detectable far-field optical signals such as amplitude and phase changes, resonance frequency shifts, or fluorescence. [63,91,92] In addition, by targeting the characteristic molecular vibrations associated with the chemical bonds of molecules, surface-enhanced Raman spectroscopy (SERS) and surface-enhanced infrared absorption spectroscopy (SEIRAS) enable chemically specific detection, [32,93,94] providing opportunities for realizing real-time studies of molecular binding dynamics and metabolic pathologies. [95,96] Building on these sensing principles, we will highlight how signal readouts can be amplified through specifically designed nanophotonic geometries with a particular focus on recently reported high-end biosensing applications, encompassing the detection of biomolecules (proteins, antigens, biomarkers), exosomes, pathogens (viruses and bacteria), and cell secretion.…”

Dielectric Walls/Layers Modulated 3D Periodically Structured SERS Chips: Design, Batch Fabrication, and Applications

“…[ 16 , 17 , 20 , 21 ] Furthermore, SERS structures by incorporating NPoM and/or MIM planar structures into the 3D periodic structures above are expected to show enhanced multiple coupling effects of LSPR and SPPs and thus effectively enhanced intrinsic EMF. [ 22 ] The combination of sub‐nanometer gaps and micrometer‐scale resonators enables plasmon interference to multiply SERS signals compared with the plasmonic structures only. [ 22 ] The propagations and behaviors of SPPs involved in the periodic dielectric structures as possible excitation sources of LSPR to remarkably enhance SERS effects were scarcely touched.…”

“…[ 22 ] The combination of sub‐nanometer gaps and micrometer‐scale resonators enables plasmon interference to multiply SERS signals compared with the plasmonic structures only. [ 22 ] The propagations and behaviors of SPPs involved in the periodic dielectric structures as possible excitation sources of LSPR to remarkably enhance SERS effects were scarcely touched. Exploring the roles of dielectrics in 3D plasmonic structures can not only enrich the structures of 3D SERS chips but also create a novel platform for addressing fundamental issues about SPP and LSPR effects involved.…”

Molecular Screening for Terahertz Detection with Machine-Learning-Based Methods

“…The enhancement of Raman scattering signals in molecular nanocavities can potentially be harnessed in a recently proposed device for converting THz [or mid-and far-infrared (MIR and FIR, respectively)] radiation to visible or nearinfrared (Vis and NIR, respectively) light [4,5], thus enabling optical detectors to be used for THz detection. To enhance the light-matter interaction, the molecules are placed in a set of two antennas operating on different scales [5,6]. A THz antenna focuses radiation at the design frequency over the molecular sample volume to enhance THz absorption via the surface-enhanced infrared absorption (SEIRA) [7] mechanism.…”