Spectrally-coded optical film for independent transmission and reflection on curved surface

Abstract

Emerging demands for anti-counterfeit security and adaptive camouflage necessitate optical films that conform to the curved transparent substrates of windows, visors, and protective eyewear. These surface-conformal films must deliver high chromatic performance while accommodating geometrical flexibility. Crucially, applications such as hidden displays and directional visual cues require distinct color outputs depending on viewing direction or polarization state. To meet this need, we present a flexible, surface-conformal dual-mode spectral-coded color film (DS-CF) that enables independent control over transmitted and reflected colors. By integrating two resonators within a multilayer thin-film structure, the DS-CF leverages both Lorentzian and Fano-type resonances to realize programmable bi-directional coloration. This design overcomes the limitations of conventional dyes and photonic structures that inherently couple transmission and reflection responses. A painting-inspired demonstration validates the vivid and high-purity color expression in both transmission (≈75%) and reflection (≈41%). Additionally, polarization-sensitive reflectance control is achieved by tailoring the deposition angle of the lossy layer. With scalable fabrication and mechanical flexibility, the DS-CF offers a versatile platform for multifunctional optical films in anti-counterfeit labeling, hidden displays, and adaptive camouflage technologies.