Enhanced transmission with coaxial nanoapertures: Role of cylindrical surface plasmons

Abstract

We simulate the optical fields and optical transmission through nanoarrays of silica rings embedded in thin gold films using the finite-difference-time-domain method. By examining the optical transmission spectra for varying ring geometries we uncover large enhancements in the transmission at wavelengths much longer than the usual cutoffs for cylindrical apertures or where the usual planar surface plasmons or other periodic effects from the array could play a role. We attribute these enhancements to closely coupled cylindrical surface plasmons on the inner and outer surfaces of the rings, and this coupling is more efficient as the inner and outer ring radii approach each other. We confirm this hypothesis by comparing the transmission peaks of the simulation with cylindrical surface plasmon ͑CSP͒ dispersion curves calculated for the geometries of interest. One important result is that a transmission peak appears in the simulations close to the frequency where the longitudinal wave number k z in the ring satisfies k z = m / L, where m is an integer and L the length of the aperture, for a normal CSP TE 1 or TM 1 mode. The behavior of the CSP dispersion is such that propagating modes can be sent through the rings for ever longer wavelengths as the ring radii approach, whereas the transmission decreases only in proportion to the ring area.

Light‐Driven Plasmonic Color Filters by Overlaying Photoresponsive Liquid Crystals on Gold Annular Aperture Arrays

“…[ 47 ] For AAAs, Haftel et al have theoretically investigated the role of CSPs in enhanced optical transmission and found that the resonant CSP wavelength increases as the annular aperture size decreases. [ 48 ] Our calculation results clearly confi rmed a similar trend. It is worth mentioning that for the PSP-induced peaks, the calculated and experimental data follow a general trend although there is a slight offset, while for the CSP-induced peaks, the experimental results deviate largely from the calculated data.…”

Optical transmission of periodic annular apertures in metal film on high-refractive index substrate: The role of the nanopillar shape

“…[1][2][3][4][5][6] Such nanostructures provide additional functionalities compared to simple circular apertures in terms of very high absolute transmission related to specific waveguided modes in annular apertures, absent in simple circular holes. Coupled to surface plasmon polariton modes on metal film interfaces, these modes provide a possibility to achieve high transmission, field enhancement as well as high extraction efficiency of light trapped in the substrates.…”

“…There have been studies considering AAA with glass as a substrate, in the near-infrared, and the visible regime. [1][2][3][4][5][6] Recently, it was experimentally demonstrated an enhanced transmission around 90%. 9 When glass is used a substrate, it is possible to take advantage of the resonance associated with the cutoff of the TE 11 mode of individual annular apertures.…”

Resonant optical transmission through hole‐arrays in metal films: physics and applications

“…The next lowest order mode can have a cutoff that is modified by adjusting the inner radius, and this influences the transmission, as described in the previous section. For real metals, the cutoff of the corresponding TE 11 -like gap-mode is influenced by the metal response as well as the gap and it has been referred to as the cylindrical surface plasmon (CSP) mode [83][84][85]. Field intensity enhancements of 600 have been calculated inside the annular holes [86].…”