Extremely high Q -factor metamaterials due to anapole excitation

Abstract

We demonstrate that ideal anapole metamaterials have infinite Q-factor. We have designed and fabricated a metamaterial consisting of planar metamolecules which exhibit anapole behavior in the sense that the electric dipole radiation is almost cancelled by the toroidal dipole one, producing thus an extremely high Q-factor at the resonance frequency. The size of the system, at the mm range, and the parasitic magnetic quadrupole radiation are the factors limiting the size of the Q-factor. In spite of the very low radiation losses the local fields at the metamolecules are extremely high, of the order of 4 10 higher than the external incoming field.

Exciting dynamic anapoles with electromagnetic doughnut pulses

“…Anapoles have been observed in microwave metamaterials [16] and dielectric nanoparticles [18], and their excitation has also been predicted in core-shell nanoparticles [23] and nanowires [24]. Moreover, anapoles have been employed to enhance nonlinear effects [25] and realize high-Q microwave metamaterials [26]. However, anapole modes are weakly coupled to freespace radiation, which renders experimental observations particularly challenging.…”

Blueshift and phase tunability in planar THz metamaterials: the role of losses and toroidal dipole contribution

“…However, the electric dipole also arises in the metamolecule and maintains the anapole mode, in accordance with the destructive interference between electric and toroidal dipole moments. The advantage is a very narrow line in the transmission spectrum of a metamaterial [8]. Here, for the first time, we consider how the planar toroidal metamolecule can be exploited as a building block for terahertz modulators.…”

“…Their exotic response is a promising platform for filling the THz frequency gap [1][2][3]. A separate class of metamaterials is the one with the toroidal response [4][5][6][7][8][9][10][11][12][13][14][15]. The toroidal observation is mediated by the excitation of currents flowing in inclusions of toroidal metamolecules, and resembles the poloidal currents along the meridians of gedanken torus [4,5].…”

“…In this paper, we consider a design of a metamaterial, discussed in Ref. 8, in tunable regime. For this purpose, we incorporate the photoconductive silicon into the metamolecule (Fig.…”

“…Such fields configuration, referred as the anapole, allows to observe the new effect of Electromagnetically Induced Transparency (EIT) [6,7], provides an extremely high Q-factor in metamaterials [8], enables a cloaking for nanoparticles [9,10], and is a platform for confirmation of the dynamic Aharonov-Bohm effect [6,7]. Recently, it was demonstrated the anapole excitation in planar metamaterials, which enabled an extremely high Q-factor in microwave [8], which gives promising opportunities for tunable metamaterials due to the strong electromagnetic fields localization within metamolecules. In this paper, we consider a design of a metamaterial, discussed in Ref.…”