Bottom‐Up Tunable Broadband Semi‐Reflective Chiral Mirrors

Abstract Conventional mirrors flip the handedness of circularly polarized light upon reflection. However, there is an increasing demand for the design and fabrication of handedness‐preserving mirrors as well as chiral reflective metasurfaces with tunable spin states of reflected photons that work in a broad wavelength range in the UV and visible domain. Most chiral mirrors fabricated up to now are prepared by top‐down techniques, such as e‐beam lithography, which are very costly and difficult to scale up to macroscopic devices. Here, an efficient bottom‐up strategy is introduced for fabricating chiral mirrors by using Layer‐by‐Layer assembly of oriented silver nanowire layers prepared by grazing incidence spraying on a semi‐reflective silver layer. The resulting chiral metasurfaces display structure‐dependent differential reflectance for circularly polarized light in a broad wavelength range in the UV, visible, and near infrared domains, reaching an extremely high figure of merit. Their differential reflectance reaches up to 95% of the maximum polarization efficiency, with the handedness of the reflected light being partially preserved. These large‐area chiral mirrors with tunable chiral reflectance open perspectives in various fields, such as in optics, sensing, and chiral light‐matter interactions.