Dual-modulation terahertz device based on amplitude and frequency in VO2 hybrid metamaterial

Abstract

Terahertz (THz) waves have great potential applications in communication, imaging, and spectroscopy fields. Effective THz modulators are highly desired to realize those functionalities. Wherein, as a kind of artificial composite material, THz metamaterials can achieve extraordinary responses to the electromagnetic wave through the geometric structure design. Nevertheless, normal metamaterials have no tunability once they have been designed and fabricated. To overcome this issue, active medias have been explored to enable the expected modulation of metamaterials under the external stimuli. Among them, phase transition materials are often used in dynamically tunable THz devices due to their intriguing properties. Particularly, vanadium dioxide (VO2) has attracted attention owing to the reversible physical properties and can exhibit insulator-to-metal transition (IMT) behavior at near room temperature. Here, we explore the strength of the resonance response and the change of spectral lineshape caused by the size variation in the metamaterial unit cell. On this basis, adding VO2 thin film can realize broadband modulation during the IMT process. Furthermore, by incorporating the VO2 patches in the gold microstructure can further achieve the dual modulation of amplitude and frequency simultaneously. The design of VO2 hybrid metamaterial can break the single function limitation of traditional metamaterial modulators, reduce material loss, and open up a new path for the development of multifunctional THz modulators.