Broadband terahertz metamaterial absorber with a tunable performance based on vanadium dioxide

A tunable terahertz metamaterial based on vanadium dioxide (VO${}_2$) is designed whose top layer is composed of four identical VO${}_2$ resonators and placed on a dielectric layer supported by a continuous metal substrate. Based on the unique phase change performance, VO${}_2$ can be dominated by thermal control to achieve tunable function. When the VO${}_2$ is in the metal state, the structure achieves a resonance bandwidth of 5.10 THz with absorption greater than 90%, ranging from 3.89 to 8.99 THz, having the relative absorption bandwidth of 79.20%. When the VO${}_2$ is in the insulation state, the absorption of structure is totally close to zero, and the maximum modulation depth reaches 98.85%. Physical mechanism of broadband absorption is discussed by analyzing the electric field distribution of absorption peak with obvious characteristics of absorption curve. Extinction ratio of the tunable broadband absorption is estimated, and the maximum extinction ratio is - 19.72 dB. Besides, influence of structural parameters on the absorption efficiency is also studied, and the results highlight that the design of different sizes will cause the change of absorption response. Tunable terahertz metamaterial based on VO${}_2$ has great potential applications in the fields of intelligent absorption and terahertz tuning.