Letter pubs.acs.org/NanoLett
Plasmon-Induced Transparency in the Visible Region via SelfAssembled Gold Nanorod Heterodimers Sushmita Biswas, Jinsong Duan, Dhriti Nepal, Kyoungweon Park, Ruth Pachter, and Richard A. Vaia* Air Force Research Laboratory, Wright Patterson Air Force Base, 2941 Hobson Way, Wright Patterson Air Force Base, Ohio 45433, United States S Supporting Information *
ABSTRACT: The phenomenon of plasmon-induced transparency holds immense potential for high sensitivity sensors and optical information processing due to the extreme dispersion and slowing of light within a narrow spectral window. Unfortunately plasmonic metamaterials demonstrating this effect has been restricted to infrared and greater wavelengths due to requisite precision in structure fabrication. Here we report a novel metamaterial synthesized by bottom-up self-assembly of gold nanorods. The small dimensions (≤50/20 nm, length/diameter), atomically smooth surfaces, and nanometer resolution enable the first demonstration of plasmoninduced transparency at visible wavelengths. The slow-down factors within the reduced symmetry heterodimer cluster are comparable to longer wavelength counterparts. The inherent spectral tunability and facile large-scale integration afforded by self-assembled metamaterials will open a new paradigm for physically realizable on-chip photonic device designs. KEYWORDS: Plasmon-induced transparency, Fano resonances, self-assembly, gold nanorod, heterodimer, metamaterial
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Bottom-up self-assembly offers a promising, low-cost alternative which starts with single crystalline nanoparticles, molecularly defined spacing, and potential for large-scale fabrication. Applying this approach, Fano resonances have been reported in the near-infrared (NIR) region for clusters of nanospheres17 and in the visible region for reduced symmetry structures consisting of sphere pairs,18 nanorod−nanosphere pairs,19 and gold nanorod (AuNR) Dolmens.20 However, determining and fabricating the ideal cluster with sufficient spectral overlap of dark and bright modes with comparable amplitudes (i.e., steep dispersion over a narrow spectral window) has been challenging. Theory implies that sharp resonances in the visible require nanoscale units (
