Tuning the 3D plasmon field of nanohole arrays

Abstract

Modern photonics is being revolutionized through the use of nanostructured plasmonic materials, which confine light to sub-diffraction limit resolution providing universal, sensitive, and simple transducers for molecular sensors. Understanding the mechanisms by which light interacts with plasmonic crystals is essential for developing application-focussed devices. The strong influence of grating coupling on electromagnetic field distribution, frequency and degeneracy of plasmon bands has now been characterized using hexagonal nanohole arrays. An equation for nanohole arrays was derived to demonstrate the strong influence of incidence and rotation angle on optical properties of 2D plasmonic crystals such as nanohole arrays. Consequently, we report experimental data that are in strong agreement with finite difference time-domain (FDTD) simulations that clearly demonstrate the influence of the grating coupling conditions on the optical properties (such as plasmon degeneracy and bandwidth), and on the distribution of the plasmon field around nanohole arrays (including tuneable penetration depths and highly localized fields). The tuneable 3D plasmon field allowed for controlled sensing properties and by increasing the angle of incidence to 30 degrees, the resonance wavelength was tuned from 1000 to 600 nm, and the sensitivity was enhanced by nearly 300% for a protein assay using surface plasmon resonance (SPR) and by 40% with surface-enhanced Raman scattering (SERS) sensors.

Fano Resonances in Thin Metallic Grating for Refractive Index Sensing with High Figure of Merit

“…We find that resonant dip for three kinds of structure period has a nearly same red-shifted when the RI of dielectric layer changes from 1.33 to 1.37. When structure period increases to 1040 nm, the amount of red-shifted of resonant dip (16.3 nm) for period P=1000 nm is somewhat lower than that of period P=960 and 1000 nm (16.7 nm), which is distinguished from that of previously reported sensing configurations [30]: the amount of red-shifted of resonant wavelength will increase as the period of structure becomes larger in the RI range studied. Similarly, Fig.…”

Tunable Plasmonic Resonances in the Hexagonal Nanoarrays of Annular Aperture for Biosensing

“…figure 8a shows the evolution of the resonant wavelength of dips A and B as a function of period P. The resonant wavelength shows a good linearity to the period (solid blue line is the linear fit of the simulated data points). As being previously reported, for hexagonal arrays of nanohole, the excitation of propagating surface plasmons on the top and bottom surfaces of Au film satisfies the condition below [34]:…”

“…Two sharp dips are indicated by A and B, respectively. Narrow full width at half maximum (FWHM) of dips A and B as small as 6.7 and 7 nm, respectively, can be achieved, which is narrower than those from the nanostructures previously published [18,19,34]. Narrow resonance is highly demanded in biochemical sensing to accurately measure variations due to the presence of the molecule.…”

Gold Elliptic Nanocavity Array Biosensor With High Refractive Index Sensitivity Based on Two-Photon Nanolithography

“…This process is called extraordinary optical transmission (EOT) [1]- [3]. The optical and plasmonic properties of metallic nanostructure arrays strongly rely on the size, shape and the refractive index of surrounding medium [4]- [6]. This attractive optical property of the metallic nanostructure arrays has led to manifold applications such as sensing, light harvesting, optical switching and fluorescence enhancement [7]- [10].…”