Temperature tunable terahertz metamaterial device based on VO2 phase transition principle

Terahertz devices play an irreplaceable role in the development of terahertz technology. The bad thing is that many natural materials are difficult to respond in terahertz band, so the devices made of them have single function. In order to realize the diversity and tunability of device functions, we designed a terahertz metamaterial device composed of thermally induced phase change material VO2. The device structure is composed of Au bottom layer, SiO2 dielectric layer and VO2 top layer. We use the three-dimensional electromagnetic simulation, and use Bruggeman effective medium theory to clarify the phase transition characteristics of vanadium dioxide, while the Drude model establishes the functional relationship between the conductivity of vanadium dioxide and temperature. The basic principle behind high absorptivity is expounded by using impedance matching theory. Through software simulation, we know that when T=313 K, the device has complete reflection ability in the whole terahertz band. When T=342 K, the average absorption rate is above 95% in the ultra wideband range of 4.71~9.41 THz, and the absorption rate reaches an amazing 0.99999 at 6.31 THz, so the maximum thermal modulation range of the device is 0.001-0.99999, which exceeds the vast majority of current absorbers. By illustrating the electric field intensity distribution on the device surface pre and post the phase transition temperature during the heating process, we substantiate the vanadium dioxide phase transition and elucidate the transformation of device performance. Furthermore, absorptivity diagrams for the device with distinct structures are depicted to further exemplify the impact of each structure on the device's absorption characteristics. We explored the influence of the geometric size of the device on the absorptivity, which provides a certain reference value for practical application. In a word, we have designed a tunable terahertz device with simple structure, high absorption rate, wide absorption bandwidth, which can be used in the fields of energy collection, electromagnetic stealth, modulation and so on.