Adjustable electromagnetically induced transparency based on terahertz metamaterial embedded with vanadium dioxide

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.