Sensing with toroidal metamaterial

Abstract

Localized electromagnetic excitation in the form of toroidal dipoles has recently been observed in metamaterial systems. The origin of the toroidal dipole lies in the currents flowing on the surface of a torus. Thus, the exotic toroidal excitations play an important role in determining the optical properties of a system. Toroidal dipoles also contribute towards enabling high quality factor subwavelength resonances in metamaterial systems which could be an excellent platform for probing the light matter interaction. Here, we demonstrate sensing with toroidal resonance in a two-dimensional terahertz metamaterial in which a pair of mirrored asymmetric Fano resonators possesses anti-aligned magnetic moments at an electromagnetic resonance that gives rise to a toroidal dipole. Our proof of concept demonstration opens up an avenue to explore the interaction of matter with toroidal multipoles that could have strong applications in the sensing of dielectrics and biomolecules.

Terahertz Sensing Based on Metasurfaces

“…As a final step, the comparison of selected works is shown in Table 1. As it can be observed, the three most recent reports [54,55,57] are the ones with higher values of FOM. If we compare the two works in which the amplitude sensitivity is used, we can observe that the AS achieved by Jáuregui-López et al in ref.…”

“…[46] Copyright 2010, AIP Publishing. [54] (center); SRR used in ref. [50] and corresponding amplitude reflection spectra (bottom) of the bare sample (black) and the coated sample with an 11 µm thick photoresist (red).…”

“…[54] Originally, toroidal resonances are related with currents flowing on a torus surface. Concretely, Gupta et al presented in 2017 a metamaterial device based on a planar toroidal dipole.…”

“…Concretely, Gupta et al presented in 2017 a metamaterial device based on a planar toroidal dipole. [54] Originally, toroidal resonances are related with currents flowing on a torus surface. To implement the toroidal characteristic in two dimensions, Gupta et al proposed a 2D metasurface made of mirrored asymmetric split ring resonators coupled through a toroidal moment due to an anti-aligned set of magnetic dipoles (see a schematic in the central panel of Figure 2c).…”

Invited Article: Terahertz microfluidic chips sensitivity-enhanced with a few arrays of meta-atoms

“…This sensitivity is comparable to a standard commercial fluorescence-based systems and it can be improved by further optimization of the structure and the periodic arrangement of meta-atoms such as Fano or toroidal resonant types. 43,44 As for the measurement of solutions having larger THz absorption coefficient, shallowing the channel depth or the reflective arrangement system for reducing the THz absorption into water will be effective. We could also confirm the quantitative measurement of trace amount of liquid solutions by comparing a simple small hole type THz chip.…”