Dynamically tunable dual-band electromagnetically induced transparency-like in terahertz metamaterial

A dynamically tunable dual-band electromagnetically induced transparency-like (EIT-like) metamaterial in terahertz region is proposed. The EIT-like metamaterial consists of a left metal strip (LMS), a right metal strip (RMS) and an asymmetric two-gap rectangular split resonator (ARSR) based on vanadium dioxide film (VO2). Two transparency windows can be observed and the maxima of transmission amplitude are 92.5% and 90.5%, respectively. The surface current distributions can well explain the physical mechanism of the dual-band EIT-like effect. In addition, the influence of structure parameters on dual-band EIT-like effect is also be discussed. The four-level tripod (FLT) system, which is make up of a Lambda-system and a control state, can validate the numerical results and explain the mechanism of the dual-band EIT-like effect better. The theoretically fitted transmission spectra are in good agreement with the simulated spectra for different conductivity of VO2. By tuning the conductivity of VO2, dual-band EIT-like effect and slow light effect can be dynamically controlled without the shift of frequency. In addition, the EIT-like metamaterial with low loss can be proved by the effective medium theory. Therefore, our dual-band EIT-like metamaterial is very promising for making multiple-band terahertz functional and slow light devices.