Bound States in the Continuum in Anisotropic Plasmonic Metasurfaces

• Published in: Nano letters Vol. 20; no. 9; pp. 6351 - 6356
• Main Authors: Liang, Yao, Koshelev, Kirill, Zhang, Fengchun, Lin, Han, Lin, Shirong, Wu, Jiayang, Jia, Baohua, Kivshar, Yuri
• Format: Journal Article
• Language: English
• Published: American Chemical Society 09.09.2020
• Subjects: plasmonic metasurfaces; Bound states in the continuum; high-Q resonances; anisotropy
• ISSN: 1530-6984; 1530-6992; 1530-6992
• DOI: 10.1021/acs.nanolett.0c01752

The concept of optical bound states in the continuum (BICs) currently drives the field of dielectric resonant nanophotonics, providing an important physical mechanism for engineering high-quality (high-Q) optical resonances in high-index dielectric nanoparticles and structured dielectric metasurfaces. For structured metallic metasurfaces, realization of BICs remains a challenge associated with strong dissipative losses of plasmonic materials. Here, we suggest and realize experimentally anisotropic plasmonic metasurfaces supporting high-Q resonances governed by quasi-BIC collective resonant modes. Our metasurfaces are composed of arrays of vertically oriented double-pillar meta-molecules covered by a thin layer of gold. We engineer quasi-BIC modes and observe experimentally sharp resonances in mid-IR reflectance spectra. Our work suggests a direct route to boost the resonant field enhancement in plasmonic metasurfaces via combining a small effective mode volume of plasmonic systems with engineered high-Q resonances provided by the BIC physics, with multiple applications to enhance light-matter interaction for nano-optics and quantum photonics.