Multi-Direction-Tunable Three-Dimensional Meta-Atoms for Reversible Switching between Midwave and Long-Wave Infrared Regimes

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 When a current is induced or withdrawn, each nanosplit ring in the surface can deform in multi directions and consequently become a closed (OFF) or an open (ON) state.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%.

Optical bistability in shape-memory nanowire metamaterial array

“…The shape-memory nanowire array reported here demonstrates how non-volatile memory characteristics can be achieved in reconfigurable metamaterial nanostructures based on bimaterial bridge actuators. [6][7][8][9] More generally, shape-memory materials provide a broad range of opportunities for active/adaptive plasmonic devices, metamaterials, gratings and photonic crystals: For example, shape-memory materials could be used to add hysteretic switching and memory functionalities to thermally actuated metamaterials, 6,8,27,28 which are typically deformed only by differential thermal expansion of different materials rather than phase transitions. Two-way shape-memory alloys 19 could enable pronounced thermal switching of photonic structures between two distinct states, even without relying on differential thermal expansion.…”

A Programmable Nanofabrication Method for Complex 3D Meta-Atom Array Based on Focused-Ion-Beam Stress-Induced Deformation Effect

“…The FIB was applied in two ways in most previous work on FIB-induced bending for 3D nanostructure. One such way is to irradiate ions as a whole without discrimination, which could realize some special fabrication or manipulation [30,[37][38][39][40][41], while the other way is to irradiate ions on a specific area in sequence, which could fabricate a 3D array one unit by one unit with low efficiency [31,35,42]. As a comparison, the newly proposed fabrication method in this paper is capable of fabricating complex 3D meta-atom arrays in a quasi-parallel way to process all the unit atoms as a whole, which brings some remarkable advantages, including a much higher efficiency as well as a significant improvement in consistency and yield of the unit atoms.…”

“…The FIB-SID technique is a newly developed method to fabricate complex 3D micro/nanostructures [29][30][31][32][33], which can be used in optical modulation, controllable drug delivery, cell capsulation, and many other areas [34]. Compared to other 3D nanostructure array fabrication methods, the FIB-SID technique can process, in real-time, complex 3D structures with nanoscale precision and is versatile for diverse materials [28,35]. However, when the scale of processing becomes large, the processing efficiency of this method remains a non-negligible challenge because of its serial processing mode, which means, as reported in our previous work [28,35], the 3D meta-atoms can only be fabricated one by one unit cell.…”

Folding 2D Structures into 3D Configurations at the Micro/Nanoscale: Principles, Techniques, and Applications

“…For external driving forces, the rigid parts can be actuated by a magnetic field, capillary force, compressive force, or cell traction force (CTF), where the hinge is only a flexible connection between the rigid parts, and the size of the as‐fabricated device is usually in the micrometer or millimeter scale. In comparison, for internal driving forces, the internal interactions within the hinge part can change its curvature and lead to folding of the rigid parts, which is sometimes referred to as “self‐folding.” The internal interactions could arise from surface tension (capillary force), material expansion/shrinking (strain gradient, phase transition in a shape memory polymer, pneumatic force), bio‐force (cell traction force), ion–solid interactions (focused ion beam), etc. The size of the device can be scaled down to quite a small scale (from millimeters to hundreds of nanometers).…”

“…Another interesting demonstration of ion beam folding structures was made by Mao et al, who used a multilayer Au/SiN film to construct active optical devices (Figure f) . Deformation of the 3D folding units was driven by the Joule heat when electric currents flow through the gold layer.…”