Optical Response of Plasmonic Nanohole Arrays: Comparison of Square and Hexagonal Lattices

Abstract

Nanohole arrays in metal films allow extraordinary optical transmission (EOT); the phenomenon is highly advantageous for biosensing applications. In this article, we theoretically investigate the performance of refractive index sensors, utilizing square and hexagonal arrays of nanoholes, that can monitor the spectral position of EOT signals. We present nearand far-field characteristics of the aperture arrays and investigate the influence of geometrical device parameters in detail. We numerically compare the refractive index sensitivities of the two lattice geometries and show that the hexagonal array supports larger figure-of-merit values due to its sharper EOT response. Furthermore, the presence of a thin dielectric film that covers the gold surface and mimics a biomolecular layer causes larger spectral shifts within the EOT resonance for the hexagonal array. We also investigate the dependence of the transmission responses on hole radius and demonstrate that hexagonal lattice is highly promising for applications demanding strong light transmission.

Ultra-narrow Line Width Polarization-Insensitive Filter Using a Symmetry-Breaking Selective Plasmonic Metasurface

“…Hexagonal lattice arrangements of nanoholes have been shown to provide sharper EOT resonances and a higher confinement of 3 E-field which make this arrangement suitable for sensing applications. 37,38 Elliptical nanohole arrays 39,40 have been investigated to provide an efficient polarisation dependent, 41 broadband response 42,43 and have found applications in biosensing due to the high sensitivity to changes in refractive index. 44 Two designs are presented in our investigation, the unit cells of which are highlighted in Figure 1.…”

Plasmonic Gold Nanohole Arrays for Surface-Enhanced Sum Frequency Generation Detection

“…A narrow peak around 962 nm for ϕ = 0° (Mode 1, FWHM 12.5 nm) and two peaks around 882 (Mode 2, FWHM 12.2 nm) and 828.5 nm (Mode 3, FWHM 40.2 nm) for ϕ = 90° were assigned to the SPP of the periodic Au NHAs, which were shift with incident angles (Figure 3 and Table S1) [17,30]. The weak and incident angle independent 630 nm (D1) and 710 nm (D2) were caused by the LSPR of the Au holes [31,32]. The corresponding quality factors Q = λ0/Δλ (where λ0 was the resonant wavelength and Δλ was the corresponding FWHM) were 77, 76 and 21 for Mode 1-3 of the Au NHAs, respectively.…”

“…Spontaneously, the resonant amplitudes An were considered as the major factor for the overall SFG spectral lineshape changes in Figure 4. The phase difference was introduced by the 4-MBN near the edges of NHAs holes with slightly different orientations [32,36]. In addition, the ratio of An for the Au NHAs and Au film is 2.8, which corresponded to 8 times enhancement of the SFG signal intensity, i.e.…”

Ultrabroadband Absorption Enhancement via Hybridization of Localized and Propagating Surface Plasmons

“…To gain further insight into the ultrabroadband absorption enhancement of the Cr-based MA, distributions of electromagnetic field, Poynting vector, and current density associated with the absorption peaks are shown in Figure 3 . As can be seen in Figure 3 a–c, the normalized amplitudes of the electric field of the absorption peaks are distinctly enhanced, and four hotspots occur at both the top and bottom edges of the Cr nanorods, indicating the excitation of LSP, which has a dipolar feature [ 57 , 58 ]. Moreover, the Poynting vector distribution shows that the energy of the incident light primarily flows and dissipates around the Cr nanorods, and more light will penetrate into the SiO 2 /Cr stacks as resonance wavelength is increased.…”