Asymmetric optical camouflage: tuneable reflective colour accompanied by the optical Janus effect

摘要

a Conceptual illustration of direction-sensitive asymmetric optical camouflage by the tuneable optical Janus effect. b, c SEM images of the Bruggeman Au film (b, top view) and CYTOP nanopillars (c, cross-sectional view) of the BEE. Scale bars, 200 nm. d Schematic illustration of light propagation within the liquid-permeable BEE and reflection and transmission coefficients at each interface. e Calculated reflective colours of the BEE upon opposite incidences (upper and lower half for reflective colours seen from the frontside and backside) as a function of fAu and neff of the dielectric region. f, g Calculated (left) and experimentally observed (right) reflective colours of BEE under neff ≈ 1.05 f and 1.35 g seen from the frontside (upper) and backside (bottom). Scale bars, 2 cm