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.