Dual-band switchable terahertz dynamic phase modulator based on coupling of resonance modes on a VO₂ metasurface

We propose a Φ-shaped resonator nested with VO₂ patches to achieve dual-band switchable phase modulation in the terahertz range. The sample is fabricated using a surface micromachining process and characterized by a terahertz time-domain spectrometer. The results indicate that, when the VO₂ is in the insulated state, two resonance peaks at 0.33 THz and 0.756 THz are observed, and thus a transparent window is formed and an EIT-like effect is produced. However, when the VO₂ is in the metallic state, the two peaks disappear and the transparent window turns to a stop-band with a central frequency at about 0.55 THz. Most importantly, the device can realize dual-band switchable dynamic phase modulation, and the maximum phase shifts of 89° and 60° are achieved at 0.36 THz and 0.72 THz, respectively. The mechanism for this is due to the coupling of resonance modes on the VO₂ metasurface. This work provides a new method for constructing multifunctional terahertz devices.