Broadband Optical Modulation Using Energy‐Recyclable Spatiotemporally Selective Deposition of Plasmonic Metals

ABSTRACT Dynamic plasmonics has gained increasing attention in integrated optics and intelligent energy systems, yet achieving simultaneously broadband and large‐amplitude modulation remains a major challenge. Here, we demonstrate an energy‐recyclable active optical technology based on broadband dynamic plasmonic modulation via spatiotemporally selective electrodeposition of lithium metal, initiated by randomized nanoseeded gold nanoparticles (Au NPs). By precisely manipulating the size and spatial distribution of the Au nanoseeds, reconfigurable transformation of lithium nanoparticles with both boosted spatial heterogeneity and well‐preserved stability is achieved, arising from the co‐existing regulation on nucleation and growth of lithium metals. This process enables reversible broadband optical modulation from near‐unity reflectance to perfect absorption state across the entire visible‐near infrared regime, with an optimal response time ∼ 1.5 s under operated current density of 9 mA/cm 2 . Moreover, leveraging the intrinsic charge–discharge energy recovery of the lithium electrodeposition system, the device achieves an energy‐recycling efficiency of ∼ 65%. These extremely integrated energy and optical information technologies highlight practical potential for next‐generation low‐powered grayscale modulation, optical encryption, and intelligent light‐harvesting devices.