Electrically Triggered VO2 Reconfigurable Metasurface for Amplitude and Phase Modulation of Terahertz Wave

Actively controlling the amplitude and phase of terahertz (THz) wave is of great significance for THz broadband wireless communication and high-resolution THz imaging. In this paper, we present a THz amplitude and phase modulator based on electrically triggered vanadium dioxide (VO ₂ ) reconfigurable metasurface. The unit cell of the device consists of three concentric split-rings-rings (SRRs) on the sapphire substrate, i.e., one VO ₂ -split-ring (VSR) and two metal SRRs. The VSR is embedded between two metal SRRs. The resonance mode, resonance intensity and surface current distribution in the unit cell can be dynamically manipulated by electrically triggering the insulator-to-metal-transition (IMT) of the VO ₂ . The sample is fabricated using a surface micromachining process and characterized by a THz time-domain-spectroscopy (TDS) system. The experimental results show that, 90 degrees phase shift is achieved in a broad bandwidth of 70 GHz. Meanwhile, the amplitude modulation depth reaches 71% at 0.79 THz. The transmission and the phase shift are calculated by an equivalent circuit model, and simultaneously simulated using a full-wave circuit simulation software based on the Method of Moments (MoM). The calculation and simulation results agree with the experimental results. The device has potential applications in THz imaging, broadband wireless communications and array phase controlling.