Active terahertz metamaterials based on the phase transition of VO2 thin films

• Pulsed laser deposition of phase changing VO2 thin films
• Hybrid metamaterial devices composed of split-ring resonators and phase changing VO2
• Tunable THz transmission with a modulation efficiency over 50%

Vanadium dioxide (VO2) thin films were prepared on single crystal sapphire substrates by pulsed laser deposition. VO2 films exhibited a significant resistivity drop (> 104 Ω-cm) and large optical transmittance change (> 60%) in the near-infrared region across their semiconductor-to-metal transition. Hybrid metamaterial devices designed for the THz frequency regime were fabricated by combining double split-ring resonators (SRRs) with phase changing VO2 films. By changing the conductivity of VO2 via temperature, the behavior of the SRR gap was adjusted from capacitive to resistive in order to modulate the THz beam transmission at their resonance frequencies. A modulation efficiency greater than 50% was achieved at the magnetic resonance frequencies (0.3 THz and 0.7 THz) in these hybrid SRR–VO2 metamaterial devices.