Abstract
The dynamical switching of a toroidal dipole resonance channel is demonstrated by tuning the Fermi level of a Dirac semimetal film sandwiched between the back substrates. As the Fermi level is increased from 30 to 150 meV, the resonance frequency is switched from 0.283 to 0.201 THz because of the transition from toroidal mode to hybrid mode. The hybrid mode is formed by the interaction between the toroidal mode and the plasmonic mode (induced by a Dirac semimetal film with metallic properties). The influence of the sandwiched dielectric layer (between the toroidal metasurface pattern and the Dirac semimetal film) on the switching effect was also investigated. This active dual-channel terahertz switching may have potential applications in advanced terahertz communication.
Highlights
Channel switching of the toroidal dipole resonance by changing the Fermi level is presented with various effects under different thicknesses of the dielectric layer
The results demonstrate that the thickness of the dielectric layer has a crucial effect on the tunable properties of the toroidal dipole metamaterial with the DSF
Toroidal dipole resonance tuned by a DSF has been shown to achieve active channel switching at terahertz frequencies
Summary
Artificial subwavelength resonator arrays have been regarded as so-called “metamaterials” to manipulate novel electromagnetic responses, and have been widely applied to electromagnetically induced transparency [1,2,3,4,5,6,7], the Fano effect [8,9,10,11,12], perfect absorption [13,14,15], polarization conversion [16,17,18], and so on. Toroidal dipoles in 2D metamaterials offer weak electromagnetic scattering compared with electric and magnetic dipoles, and could reduce the radiative loss from an electric dipole [22]. Such a configuration is easy to fabricate by conventional photolithography and a lift-off process. Channel switching of the toroidal dipole resonance by changing the Fermi level is presented with various effects under different thicknesses of the dielectric layer. The results demonstrate that the thickness of the dielectric layer has a crucial effect on the tunable properties of the toroidal dipole metamaterial with the DSF. This study shows that channel switching of the toroidal dipole resonance has the potential to be applied to terahertz information exchange and terahertz communication
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