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Traditional three-dimensional (3-D) plasmonic metamaterials with metallic structures – artificial materials that exploit coherent delocalized electron oscillations known as surface plasmons produced from the interaction of light with metal-dielectric materials – exhibit unique electromagnetic properties not found in natural materials, such as extraordinary transmission beyond the diffraction limit, efficient light-harvesting ability, plasmonic color filtering, and the ability to control the reflection or transmission direction of a light beam. However, they are difficult to fabricate, have a narrow usable bandwidth due to their resonant character, and exhibit low optical efficiency due to the inherent metal absorption. While two-dimensional metasurface structures have been proposed in an attempt to address these functional limitations, they still require complex designs and sophisticated fabrication procedures.

Recently, scientists at Shanghai Jiao Tong University proposed a unique method for controlling photons with a 1-D metasurface that, by integrating diffraction, waveguide, and plasmonic effects, is fundamentally distinct from 2-D or 3-D methods. The 1-D metasurface they presented, based on bilayered metallic nanowire gratings, behaves as an ideal polarized beam splitter that produces highly anisotropic strong negative reflection for transverse-magnetic (TM) light and efficient reflection for transverse-electric (TE) light. (Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies identical properties in all directions.) Moreover, by combining this feature with the fringed structure of a hologram, the researchers demonstrated a higher-security anti-counterfeit metasurface holograph, that can be decoded only by TM light.

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