Electromagnetic induced transparency (EIT) in terahertz band can achieve group delay and transparent window, which is attractive in biosensing field. In this paper, based on the phase transition properties of vanadium dioxide (VO2), an EIT with metasurface is designed to adjust the frequency position of transparent window. The unit cell of the metasurface consists of a cut wire (CW) resonator embedded with VO2 and two C-shaped ring resonators. The simulations show that when VO2 is in the insulating phase, the EIT window appears at 0.58-0.74 THz. While VO2 is in the metallic phase, the EIT window is located at 0.37-0.50 THz. The proposed structure has the active regulation of the EIT frequency band, which provides great potential for the sensitivity detection in THz.
An adjustable electromagnetically induced transparency (EIT) metamaterial embedded with vanadium dioxide (VO2) is demonstrated at terahertz (THz) region. The unit cell of metamaterial consists of a quartz substrate and two parallel wire metal resonators with different length on top layer. The two ends of the shorter wire metal resonator are filled with VO2. The short wire metal resonator (SWMR) and the long wire metal resonator (LWMR) are acted as bright mode, which can be directly coupled with the incident THz wave to produce the EIT. Due to the insulator-to-metal transition of VO2, the amplitude of EIT peak can be actively modulated and the modulation is implemented only in the EIT window with slight changes in transmission dips. When VO2 is transformed from the insulating phase to the metallic phase with the conductivity changed from 2×102 S/m to 2×105 S/m, the amplitude of the EIT peak can decrease from 0.91 to 0.03, which indicates that the EIT metamaterial achieves a large modulation depth. The physical mechanism of this phenomenon is explained by the magnetic field and current distributions. In addition, it is found that the slow-light effect gradually weakens and disappears with VO2 changing from the insulating phase to the metallic phase. This work provides a strategy to achieve an adjustable EIT effect in THz metamaterial structure embedded with VO2 and exhibits potential applications in THz modulators and slow-light devices.
This paper proposes a novel terahertz metamaterial modulator utilizing vanadium dioxide phase-change materials, which adopts three nested square split rings as a unit cell. The modulator can achieve dual functions of band-stop filter and bandpass filter by vanadium dioxide filled in the gap of split ring changing phase. The simulation results show that the central frequency of the modulator is around 0.83 THz, whether the modulator is at band-stop state or band-pass state. The modulator shows that the -3 dB bandwidth reaches to 30 GHz at the state of band-pass, and that the -20 dB bandwidth reaches to 160 GHz at the state of band-stop.
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