A novel thin-film single-layer structure based on resonant waveguide gratings (RWGs) allows to engineer selective color filtering and steering of white light. The unit cell of the structure consists of two adjacent finite-length and cross-talking RWGs, where the former acts as in-coupler and the latter acts as out-coupler. The structure is made by only one nano-imprint lithography replication and one thin film layer deposition, making it fully compatible with up-scalable fabrication processes. We characterize a fabricated optical security element designed to work with the flash and the camera of a smartphone in off-axis light steering configuration, where the pattern is revealed only by placing the smartphone in the proper position. Widespread applications are foreseen in a variety of fields, such as multifocal or monochromatic lenses, solar cells, biosensors, security devices and seethrough optical combiners for near-eye displays.
Giorgio Quaranta, Guillaume Basset, Olivier J. F. Martin, and Benjamin Gallinet, "Steering and filtering white light with resonant waveguide gratings," Proc. SPIE 10354, Nanoengineering: Fabrication, Properties, Optics, and Devices XIV, 1035408 (Presented at SPIE Nanoscience + Engineering: August 09, 2017; Published: 31 August 2017); https://doi.org/10.1117/12.2272683.
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