In this paper, a terahertz tunable filter based on vanadium dioxide with a H-type structure is designed. The dielectric layer of the filter is quartz glass and the metal layer is composed of aluminum and vanadium dioxide. Using the phase transition characteristic of VO2, the single band and double band of filter can be switched. When VO2 is the insulating phase, the filter is in single-pass state with a transmission rate of 0.97 and a -3dB bandwidth of 1.71THz; when VO2 is the metallic phase, the filter is in double-pass state, the transmission rate of both passbands reaches above 0.8, and the -3dB bandwidth at the center frequency is 0.89THz and 1.17THz respectively.
Electromagnetic induced transparency (EIT) refers to the phenomenon of a sharp transmission window in a broad absorption profile, which was first discovered in the interference between the electronic transition paths of three energy levels. In this work, a metasurface structure with EIT is designed by coupling a dark-like mode and a bright mode. In order to make its resonance intensity dynamically adjustable, the metasurface structure in this paper adds a structure composed of vanadium dioxide (VO2) to the original EIT structure. When vanadium dioxide is at different temperature, its conductivity is different, and the degree of participation in metasurface resonance is different. Thus, the dynamic tuning of the EIT resonance intensity is realized, and the modulation depth can reach 76.18%.
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.
A switchable narrowband THz metasurface filter based on vanadium dioxide (VO2) is demonstrated which can be switched between the “ON” and “OFF” state by applying a bias current to VO2. In the initial “ON” state without applying the bias current, the transmittance of the filter is greater than 80% from 0.72 to 0.78 THz and reaches a maximum of 92% at the center frequency of 0.75 THz. After applying 300 mA current to VO2, the filter is in the “OFF” state and the transmittance is almost zero over the entire frequency range from 0.4 to 1.1 THz. Furthermore, considering the influence of the substrate thickness of the filter on the actual application of the device, the response of the filter with different thicknesses of the substrate is numerically simulated, and the results show that the filter performance is still good when the thickness of the substrate increases to 500 μm.
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.
In this paper, a novel terahertz modulator using the phase transition characteristics of vanadium dioxide to achieve both band-pass and band-stop filter states is proposed. The regular hexagonal split-ring is used as a unit structure, and the center frequency can be changed by changing the size of the regular hexagon. The simulation results show that any frequency between 0.1~1THz can be used as its center frequency. In the case of 140 um regular hexagon cell, the band-pass filter state shows that the -3dB bandwidth reaches to 100 GHz, and the band-stop filter state shows that the -20dB bandwidth reaches to 75 GHz. Furthermore, a mirror-type regular hexagonal structure is designed as unit cell, which can improve the modulator performance in both states.
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