Active Chiral Plasmonic Metasurfaces

Chiral plasmonics offers a powerful means to control light-matter interactions based on their unique polarization-sensitive chiroptical characteristics, enabling a wide range of applications, including molecular sensing, holographic encryption, and optical filters.[1] In order to fully exploit the potential of chiral plasmonics for industrial applications, it is crucial to develop their active system that can respond to external stimuli and thus allow us to dynamically control their chiroptical responses. However, such active chiral plasmonics are still in their early stages of development.<br/>Here, we present an active chiral plasmonic metasurface capable of dynamically controlling the chiroptical response through combinatorial modulation of both the state of light polarization and an external electrical input. The metasurface consists of a wafer-scale array of chiral nanohelices grown using a physical shadow growth technique, with a conductive polymer shell polymerized around the entire surface of helices. The intrinsic dissymmetry factor of this chiral plasmonic metasurface exceeds 0.1, leading to rich polarization-dependent colors. To achieve further extended color dynamics, we electrochemically control the redox state (i.e., refractive index) of the conductive polymer shell, thereby inducing changes in the plasmonically resonating colors of the nanohelices.[2] Remarkably, in conjunction with controlling the state of the light polarization, we achieve full-color dynamics from the single chiral plasmonic metasurface, driven by just input voltages of less than 1 V, highlighting its potential applications in electrochromic displays and filters.<br/>In this presentation, we will discuss the successful fabrication of these chiral plasmonic metasurfaces and provide a comprehensive characterization of their active chiroptical properties. The proof-of-concept applications will also be presented, featuring their impressive fidelity for active coloration.<br/><br/>[1] J. H. Han et al, Adv. Mat. 2023<br/>[2] J. Peng et. al, Sci. Adv. 2019, <b>12</b>, eeaw2205