Active Phase Transition via Loss Engineering in a Terahertz MEMS Metamaterial

Controlling the phase of local radiation by using exotic metasurfaces has enabled promising applications in a diversified set of electromagnetic wave manipulation such as anomalous wavefront deflection, flat lenses, and holograms. Here, we theoretically and experimentally demonstrate an active phase transition in a micro-electromechanical system-based metadevice where both the phase response and the dispersion of the metamaterial cavity are dynamically tailored. The phase transition is determined by the radiative and the absorptive losses in a metal–insulator–metal cavity that obeys the coupled-mode theory. The complete understanding of the phase diagram in a reconfigurable configuration would open up avenues for designing multifunctional metadevices that can be actively switched between different phases leading to a plethora of applications in polarization control, beam deflectors, and holographic metamaterials.

An active phase transition based on a terahertz micro-electromechanical system metamaterial is experimentally demonstrated where the radiative and nonradiative loss channels are manipulated to switch the resonant operation between underdamped and overdamped states. Several applications can be enabled by controlling the phase response with the complete understanding of the phase diagram in reconfigurable metamaterials.

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