Annular nanoplasmonic void arrays as tunable surface enhanced Raman spectroscopy substrates

Abstract

We report the use of annular nano-voids in a metallic thin-film as programmable molecular sensors for surface-enhanced Raman spectroscopy (SERS). To date, research into these structures has focused on the exploration of their extraordinary optical transmission attributes. We now show that by using advanced lithography and simulation tools, we can generate a porous SERS material for molecular interrogation. Using ultra-thin annular structures, rather than simple circular holes, allows us to reduce both the volume and cross-sectional area of the void, maximizing the electric-field confinement, while, importantly for SERS, producing resonant conditions in the visible region of the spectrum. By comparing our annular films with conventional circular films with the same resonant frequency, we show a significant improvement in the efficiency of Raman scatter, creating stronger signals that also contain more spectral information.

Dual Color Plasmonic Pixels Create a Polarization Controlled Nano Color Palette

“…It is already well established that in such circumstances the plasmon tunnels through the aperture and decays to radiant photons upon penetrating the metal film. [19][20][21][22][23][24] By varying the size, shape, thickness and periodicity of the array, it is known that the permitted plasmon coupling frequency can be tuned, dictating the color of the transmitted light. 15,17,25,26 Typically, plasmonic cavity-aperture filters are comprised of circular nano-holes tuned to operate efficiently at a single wavelength.…”

“…At normal light incidence, the nanoapertures act as grating couplers, providing photon–plasmon momentum matching to allow surface plasmon resonances (SPR) at the metal/dielectric interface. It is already well established that in such circumstances the plasmon tunnels through the aperture and decays to radiant photons upon penetrating the metal film. − By varying the size, shape, thickness and periodicity of the array, it is known that the permitted plasmon coupling frequency can be tuned, dictating the color of the transmitted light. ,,, …”

A Chiral Plasmonic Metasurface Circular Polarization Filter

“…Arrays of nanoscale apertures in thin metallic films, when compared to their nanoparticle counterparts, are of particular interest for sensing and telecommunication applications because of the relatively high transmission contrast and background field reduction achievable with these devices. Furthermore, the reduced mode LSP volume inside the resonant aperture could lead to a reduction in the amount of analyte required for remote sensing applications [13]. The devices presented here are sensitive to visible wavelengths, but can be scaled to operate at longer wavelengths if required.…”

Integration of tunable two-dimensional nanostructures on a chip by an improved nanosphere lithography method

“…After deposition of a layer of metal film, surface plasmon polariton resonances (SPPs) can be excited on the produced 2D patterns. Thus, these nano-structures can be used as plasmonic components, such as for solar cell components, plasmonic absorbers, surface-enhanced Raman scattering (SERS) substrates [10,22], and other chemical/ bio-sensors [11,23].…”