Abstract
Currently, metasurfaces (MSs) integrating with different active materials have been widely explored to actively manipulate the resonance intensity of multi-band electromagnetic induced transparency (EIT) windows. Unfortunately, these hybrid MSs can only realize the global control of multi-EIT windows rather than selective control. Here, a graphene-functionalized complementary terahertz MS, composed of a dipole slot and two graphene-integrated quadrupole slots with different sizes, is proposed to execute selective and active control of dual-band electromagnetic induced reflection (EIR) windows. In this structure, dual-band EIR windows arise from the destructive interference caused by the near field coupling between the bright dipole slot and dark quadrupole slot. By embedding graphene ribbons beneath two quadrupole slots, the resonance intensity of two windows can be selectively and actively modulated by adjusting Fermi energy of the corresponding graphene ribbons via electrostatic doping. The theoretical model and field distributions demonstrate that the active tuning behavior can be ascribed to the change in the damper factor of the corresponding dark mode. In addition, the active control of the group delay is further investigated to develop compact slow light devices. Therefore, the selective and active control scheme introduced here can offer new opportunities and platforms for designing multifunctional terahertz devices.
Highlights
Over the last few decades, the electromagnetic induced transparency (EIT) first observed in the atomic system has aroused a lot of interest because it allows the enhancement of transmission within a narrow frequency range along with strong dispersion properties and displays promising engineering prospects [1,2,3]
We propose a scheme to obtain a dual-band electromagnetic induced reflection (EIR) window in a graphenefunctionalized complementary THz MS consisting of two dolmen-like slot structures with different sizes and two graphene ribbons connecting to different top gates
The selective and active control of two EIR windows are further investigated by tailoring the Fermi energy of the corresponding graphene ribbons via electrostatic doping
Summary
Over the last few decades, the electromagnetic induced transparency (EIT) first observed in the atomic system has aroused a lot of interest because it allows the enhancement of transmission within a narrow frequency range along with strong dispersion properties and displays promising engineering prospects [1,2,3]. The EIT-like effect in terahertz (THz) MSs has been widely investigated and experimentally demonstrated by bright–dark mode coupling [6,7] or bright–bright mode coupling [8,9] Most of these structures can only realize a single transparency window, in which the resonance strength of the window is fixed after fabrication, restricting their application fields [10]. We propose a scheme to obtain a dual-band EIR window in a graphenefunctionalized complementary THz MS consisting of two dolmen-like slot structures with different sizes and two graphene ribbons connecting to different top gates. The selective and active control of two EIR windows are further investigated by tailoring the Fermi energy of the corresponding graphene ribbons via electrostatic doping.
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