Reversible composite terahertz modulator based on VO2 phase transition

In recent years, terahertz metamaterials have attracted great attention due to their widely application in frequency selector, filter, and other optical devices. Vanadium dioxide as the promising thermal memory material, has been used in making terahertz modulation device because of its well-known insulator-to-metal transition triggered by thermal, optical, and electrical. Here, we designed a composite metamaterial with three rings structure, where outer and inner rings are set to be ideal metallic gold and the middle ring is replaced by VO2. Using finite-difference time-domain method, we theoretically studied the variety of THz transmitted spectra during the insulator-to-metal transition of VO2 and its influence on the resonance coupling effect. When VO2 is in insulating phase, there are two resonant dips in spectrum. However, as VO2 undergoes an insulator-to-metal transition, the low-frequency resonance gradually moves to high frequency and finally splits into two. Our obtained results indicate the reversible terahertz modulation can be achieved by combining metamaterials with phase transition material.