Single sub-wavelength aperture with greatly enhanced transmission

Abstract

High transmission efficiency at terahertz (THz) frequency is reported for a single aperture with sub-wavelength dimensions having a Siemensstar shape, microfabricated in the metal film and surrounded by periodic surface corrugations. Compared to theoretical predictions for a simple circular hole of equivalent area, up to ∼10 6 transmission enhancements were observed experimentally. Such a pointed-shape aperture was also used to obtain the detailed profile of the electric field distribution in the focal plane of a linearly polarized focused THz beam. Applications could be extended to other regions of the electromagnetic spectrum by appropriate scaling of aperture microstructure. Contents

Terahertz wave interaction with metallic nanostructures

“…Also, localizations of incident/transmitted light before/after the gap can be incorporated to increase the field enhancement in the gap [322][323][324][325] (Figure 30). The other example is to make use of hybridization of a gap with plasmonic metastructures or metaelements [71,114,191,[320][321][322][323][324][325][326][327][328][329] that results in intensive localization of electric field in the form of surface waves such as vortexplasmon and spoof surface plasmon modes.…”

“…] is equivalent to enhancing the magnetic field of light around rod and patch antennas [93][94][95][96][97][98][99][100]. Although a metal film in THz frequency is neither perfect conductor nor infinitely flat, various areas of THz research [2,99,[101][102][103][104][105][106][107][108][109][110][111][112][113][114][115], including THz plasmonics [116][117][118][119][120][121][122][123] and metamaterials [124][125][126][127][128][129][130], implicitly use this principle, which remains true in its spirit if not in its rigor. One of the earliest theoretical accounts on the light-aperture interaction had been made by Sommerfeld's half-plane problem [131][132][133] that was revisited by Bethe and Bouwkamp to deal with small apertures in infinitely thin perfect conducting plates [134]…”

Breaking Bullseye’s Symmetry for Axial Field Focusing

“…This field enhancement, first observed in optical regime [3] then in the THz and microwave range [4,5], leads to possible applications like near field imaging [6,7], high gain antenna [8,9], waveguide coupler-decoupler [10] and chemical sen-D. Armand ( ) · T. Tanaka Japan Science and Technology Agency, CREST, Kawaguchi, 332-0012, Japan e-mail: damien.armand@gmail.com sors. In order to enhance the field even more, such special designs at the center of the bullseye were proposed as the resonant element [11], the bowties [12] and the Siemens-star [13] shape. However, in these previous works, it is the electric field polarized in the plane of the substrate that is focused.…”

A terahertz band-pass resonator based on enhanced reflectivity using spoof surface plasmons

“…[7][8][9][10][11][12]). Thus the concept of SSPs has attracted a great deal of recent interest in applications such as squeezing a THz beam into a subwavelength volume [4,13], enhancing transmission through a subwavelength aperture or slit [14][15][16][17] or improving the collimation of the spatial mode of a THz quantum cascade laser [18,19].…”