Low-Power Electrochemical Modulation of Silicon-Based Metasurfaces

The incorporation of active materials into metasurface architectures enhances functionality by enabling active tuning of the electromagnetic response, a freedom that would be highly beneficial in many applications at visible frequencies. Here, we employ Li-ion insertion into amorphous silicon, a traditional battery chemistry, to realize modulation of visible frequency metasurfaces utilizing both a change in refractive index and accompanying lattice expansion. We quantify the refractive index change upon lithiation, achieving Δn = 0.12 at 500 nm and employ the material in a metasurface, demonstrating reversible color bleaching with accessible intermediate states. This is achieved at a power consumption of less than 120 μW/cm². Given the low power consumption and potential for energy recycling, dynamic electrochemical metasurfaces are uniquely suited for applications in the visible spectrum that demand small form factor and low power usage.