No abstract

We introduce an electromechanically tunable metasurface composed of an array of three-dimensional nanosplit-rings for reversible and large-range changes of optical characteristics in infrared (IR) regime. When a current is induced or withdrawn, each nanosplit ring in the surface can deform in multi directions and consequently become a closed (OFF) or an open (ON) state. Theoretical and experimental results manifest that, as the metasurface is dynamically manipulated between the ON and OFF states, the corresponding resonance absorption will reversibly switch between the long wave (around 10.4 μm) and midwave (around 6.3 μm) IR regimes, two key IR spectral windows, and the reversible relative reflection changes can reach up to 95%.

3D structures with characteristic lengths ranging from nanometer to micrometer scale often exhibit extraordinary optical properties, and have been becoming an extensively explored field for building new generation nanophotonic devices. Albeit a few methods have been developed for fabricating 3D optical structures, constructing 3D structures with nanometer accuracy, diversified materials, and perfect morphology is an extremely challenging task. This study presents a general 3D nanofabrication technique, the focused ion beam stress induced deformation process, which allows a programmable and accurate bidirectional folding (-70°-+90°) of various metal and dielectric thin films. Using this method, 3D helical optical antennas with different handedness, improved surface smoothness, and tunable geometries are fabricated, and the strong optical rotation effects of single helical antennas are demonstrated.