Reversible Multi-Degree-of-Freedom Photocontrol over Chiroptical Responses of Chiral Plasmonic and Mie-Resonant Nanostructures

Abstract

Chiral nanostructures have attracted considerable interest for applications in enantioselective sensing and catalysis, circularly polarized light (CPL) detection, filtering, and emission, as well as metamaterials. Dynamic and reversible control of their chiroptical properties would greatly expand their functionalities. Here, we fabricated chiral TiO2–Ag nanostructures combining Mie and plasmonic resonances through CPL-driven photonic nanofabrication beyond the diffraction limit, and demonstrated reversible photonic control of their chiroptical responses across the UV–visible region. Switching between achiral and chiral states was achieved using unpolarized light and CPL, while handedness was reversibly switched using right- and left-handed CPL. More importantly, the chiroptical response could be spectrally rewritten by changing the CPL wavelength. Furthermore, humidity control enabled switching between rewritable and stable modes. The resulting nanostructures provide a versatile platform for multi-degree-of-freedom control over chiroptical properties encompassing handedness, intensity, wavelength, and their rewritability, and offer promising opportunities for tunable metamaterials, reconfigurable optoelectronic devices, high-density data storage, and rewritable concealed-image display.