A fluid-guided printing strategy for patterning high refractive index photonic microarrays

High refractive index (HRI, n > 1.8) photonic structures offer strong light confinement and refractive efficiencies, cover the entire visible spectrum and can be tuned by designing geometric arrayed features. However, its practical applications are still hindered by the applicability and material limitation of lithography-based micro/nano fabrication approaches. Herein, we demonstrate a fluid-guided printing process for preparing HRI selenium microarrays. The microstructured flexible template is replicated from the diced silicon wafer without any lithography-based methods. When heated above the glass transition temperature, the flow characteristics of selenium endows the structure downsizing and orientation patterning between the target substrate and the template. Near 10 times narrowing selenium microarrays (1.9 μm width) are patterned from the non-lithography template (18 μm width). HRI selenium microarrays offer high refractive efficiencies and strong optical confinement abilities, which achieve angle-dependent structurally coloration and polarization. Meanwhile, the color difference can be recognized under the one degree distinction of the angle between incident and refracted light. This printing platform will facilitate HRI optical metasurfaces in a variety of applications, ranging from photonic sensor, polarization modulation to light manipulation.