Low-Voltage Triggered VO2 Hybrid Metasurface Used for Amplitude Modulation of Terahertz Orthogonal Modes

Actively tuning of terahertz (THz) waves through hybrid metasurface has important applications in THz communication, imaging, and modulation. In this paper, we propose a vanadium dioxide (VO2) hybrid metasurface to realize amplitude modulation of THz orthogonal modes at low triggering voltage. The unit cell of the hybrid metasurface consists of two identical gold crosses and a central bar. And two rectangular VO2 patterns are symmetrically embedded in the gaps of the crosses. The performance of the hybrid metasurface is simulated and optimized by using full wave electromagnetic calculation software. The sample is fabricated using a surface micromachining process and characterized by a THz time-domain-spectroscopy (TDS) system. The experimental results show that, the amplitude modulation depth reaches 68% in the range of 0.1~0.8 THz for transverse-magnetic (TM) mode. Moreover, the hybrid metasurface changes from the transparency to the stopband near 0.43 THz for transverse-electrical (TE) mode. A switching time of 1.9 s is achieved when the triggering current is 520 mA and the voltage is 3.65 V. Most importantly, a fast response area is found. If the metasurface is biased with a current of 430 mA near the fast response area, it's easy to switch quickly. This work paves a new way for the miniaturization and integration of electronic-controlled THz switches and modulators.