Resonant Far- to Near-Field Channeling in Synergetic Multiscale Antennas

Abstract

Enhancing light−molecule interactions requires the efficient transfer of energy between the laboratory macroscale and the molecule nanoscale. Multiscale designs have been proposed as a means to efficiently connect these two worlds. Metallic sphere-segment void (SSV) cavities constitute plasmonic substrates in which light wavelength scale cavity-like modes and nanoscale roughness operate in conjunction as a multiscale antenna to provide larger surface-enhanced Raman scattering efficiency than the two mechanisms considered separately. We study the selective resonant coupling to cavity modes with different spatial distributions in SSV arrays with tailored nanoscale roughness. Cavity modes that are spatially more confined to the surface are demonstrated to lead to more efficient channeling of energy from the far to the near field, a synergy that scales with the degree of roughness. Finiteelement modeling of the spatially varying local fields in rough SSV arrays allows for a microscopic description of the results, opening promising paths for the design of spatially and spectrally optimized multiscale antennas for efficient sensing with far-to near-field channeling of light.

Attenuated total reflection‐cascading nanostructure‐enhanced Raman spectroscopy on flat surfaces: A nano‐optical design

“…In this article, we report a work along with the direction of Van Duyne's strategy on borrowing SERS effect and based on the strategy of cascading optical coupling by the hierarchical structure integrating a subwavelength optical antenna and a deep-subwavelength optical antenna for high-efficiency optical coupling. [18,54,61,62] We theoretically design an ATRcascading nanostructure-enhanced Raman spectroscopy (ATRc-NERS) configuration for the much higher sensitivity. The SERS-active nanostructures such as bare Au or Ag NPs, SHINs, further focus the subwavelength light into the deep-subwavelength region, that is, the nanostructure-substrate nanogaps.…”

Facilely Flexible Imprinted Hemispherical Cavity Array for Effective Plasmonic Coupling as SERS Substrate

“…It is reported that the electromagnetic field intensity is inversely proportional to the distance parameter, which means that the effective SERS signal is generated on the premise that the molecule is located in the confined area around the plasmonic material [10]. Various types of SERS substrate structures ranging from nanoparticle (NP) aggregates [11][12][13][14][15], multidimensional structure [16][17][18][19][20] and composite substrate [21][22][23][24][25][26][27][28][29] were prepared to explore the better enhancement factor (EF) under various conditions. Among them, the cavity system has been paid more and more attention because of its unique light trapping characteristics [30][31][32][33][34][35][36][37][38].…”