Adaptive THz metamaterials activated by phase-transition materials driven MEMS

We have developed adaptive THz metamaterials based on phase-transition materials driven microelectromechanical systems (MEMS) designs. By manipulating the temperature of the phase transition material vanadium dioxide (VO₂), we can realize dramatic geometrical changes in the structure, enabling large modulation of the THz response. Because of the geometrical deformation, the structure coupled to various resonances exhibits tunable interactions and strong polarization modulation on the incident THz waves.

The metamaterials take advantage of VO₂'s ability to expand or shrink significantly during its phase transition. By pairing it with other thin film materials, we created multi-layered cantilever unit cells with customizable and controllable bends based on VO₂'s phase change. Furthermore, this volumetric change is a completely reversible process.

In our design, we showcase spiral cantilevers with spiral shapes that react strongly with the incoming THz waves. Once fabricated, these spirals can move in the vertical direction under control while the anchoring area remains in a fixed position. All components together form adaptable materials that provide switchable chirality and dynamic tunability. When the structures interact with incident THz beams, they perform strong and dynamic polarization modulation with large azimuth rotation angle change and ellipticity angle change.

The operation of these metamaterials mandates a modest thermal modulation of approximately 30 °C adjacent to ambient conditions, via strategies like global or Joule-induced heating. In essence, the THz metamaterials, harmonized with the VO₂-driven MEMS mechanisms, offer an approach for modulating THz waves with high modulation depth. With their versatile design, dynamic tunability, facile operational mechanisms, and enduring robustness, these metamaterials are suited for THz applications such as radar, communications, and imaging systems.