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This study proposes a terahertz metamaterial structure composed of a silicon–graphene–silicon sandwich, aiming to achieve quadruple plasmon-induced transparency (PIT). This phenomenon arises from the interaction coupling of bright–dark modes within the structure. The results obtained from the coupled mode theory (CMT) calculations align with the simulations ones using the finite difference time domain (FDTD) method. Based on the electric field distributions at the resonant frequencies of the five bright modes, it is found that the energy localizations of the original five bright modes undergo diffusion and transfer under the influence of the dark mode. Additionally, the impact of the Fermi level of graphene on the transmission spectrum is discussed. The results reveal that the modulation depths (MDs) of 94.0%, 92.48%, 93.54%, 96.54%, 97.51%, 92.86%, 94.82%, and 88.20%, with corresponding insertion losses (ILs) of 0.52 dB, 0.98 dB, 1.37 dB, 0.70 dB, 0.43 dB, 0.63 dB, 0.16 dB, and 0.17 dB at the specific frequencies, are obtained, achieving multiple switching effects. This model holds significant potential for applications in versatile modulators and optical switches in the terahertz range. [ABSTRACT FROM AUTHOR]

In this research, a metamaterial structure composed of graphene sandwich structure is put forward to achieve triple plasmon-induced transparency. This phenomenon is generated by brightâ€"bright modes interaction in the proposed structure, and the results calculated though couple mode theory are consistent with the simulation ones using finite difference time domain method. In addition, the effects of graphene Fermi level and scattering rate on the transmission spectrum are also discussed. It is found that the five-fold switching effects are achieved with the modulation depths (MDs) of 92%, 91%, 95%, 90% and 94%, respectively. What is more, the different graphene strip can also be adjusted by changing Fermi levels to achieve the switching effects with the MDs of 98% and 97%. This model has the prospect to be applied in multi-functional modulators and optical switches in terahertz band. [ABSTRACT FROM AUTHOR]

• Single and dual dynamic tunablePIT in terahertz frequency have been achieved through the mode couplings. • The transmission , the bandwidth and the frequency of the PIT window can be dynamically controlled through the Fermi level of graphene. • The MD of the switching effect of single PIT is up to 89%, while multiple switching effects are also achieved with the MDs of 57%, 67%, and 61%, respectively. We put forward an uncomplicated and novel graphene structure, which produces single and dual dynamic tunable plasmon induced transparency (PIT) in terahertz frequency through the coupling of bright-bright modes and bright-dark modes. The structure is studied theoretically by using the coupled mode theory (CMT), which is consistent with the finite difference time domain (FDTD) simulation one. The Fermi level of graphene is investigated to dynamically control the transmission of the PIT peak at the center frequency, and the modulation depth of this switch effect is up to 89%. Besides, the bandwidth and frequency of the PIT can also be altered through the Fermi level. Furthermore, multiple switching effects are achieved with the modulation depths of 57%, 67%, and 61%, respectively. We believe that this structure has a good application prospect in the communication and sensing areas. [ABSTRACT FROM AUTHOR]

• In this paper, single and multiple on-line tunable PIT windows have been achieved and investigated by using L-shape-based graphene structures. • Firstly, a single PIT is achieved through the combination of a graphene strip and a L-shape graphene-rectangular block. The modulation depth of the amplitude is 74.9% and the polarization extinction ratio value is 11.34 dB for this PIT window. • Secondly, dual or triple PIT windows are obtained by adding graphene strips with different lengths. • The proposed structure has excellent switching performance, and the maximum modulation depth of the optical switch reaches 97.3%, which can significantly improve the practicability and compatibility of the devices. A graphene-based metamaterial structure, consisting of a graphene strip (GS) and a L-shaped graphene-rectangular block (GRB), is proposed to generate the plasmon-induced transparency (PIT) effect. The potential physical properties of the PIT effect are analyzed by using the coupled mode theory (CMT). The PIT has the unique characteristics of controlling light propagation through the static and dynamic regulations, resulting in a prospective switching application. The performance of the optical switch is evaluated through different parameters, including the geometric size, Fermi level and polarization angle. The modulation depth of the amplitude can reach 74.9% with a specific Fermi level, while the maximum polarization extinction ratio can reach 11.34 dB. Furthermore, dual and triple PIT effects are achieved by the designing and optimizing the structure. The maximum multiple switching effect is obtained with a modulation depth of 97.3%, which has a promising prospect in terahertz optical switches. [ABSTRACT FROM AUTHOR]

Firstly, in this paper, the proposed structure is composed of a transverse graphene rectangular cavity and a vertical graphene rectangular cavity, so as to produce the plasmon-induced transparency (PIT) phenomenon. The PIT of graphene metamaterials is theoretically explored by using the finite-difference time-domain (FDTD) simulation and the coupled-mode-theoretical (CMT) analysis. Then, by adjusting the Fermi level of graphene, the PIT window is dynamically adjusted, so that the structure can be used as an optical switch. Furthermore, the refractive index sensitivity of the PIT window is investigated and the simulation results show that a sensitivity of 2.725 THz/RIU is achieved. In addition, multiple PIT windows are also generated by adding additional matched L-type graphene strips. Finally, the proposed structure may enlighten the developments of dynamically tuned terahertz devices. • We have investigated a multiple PIT-effect device by using multiple L-shape graphene strips. • By modulating the Fermi level of graphene, an optical switch is realized with an MDA of 47.9% at 6.72 THz. • A refractive index sensitivity of 2.725 THz/RIU has been achieved in the proposed structure. [ABSTRACT FROM AUTHOR]