title: Tunable multiband metasurfaces by moiré nanosphere lithography.
abstract: Moiré nanosphere lithography (MNSL), which features the relative in-plane rotation between two layers of self-assembled monodisperse nanospheres as masks, provides a cost-effective approach for creating moiré patterns on generic substrates. In this work, we experimentally and numerically investigate a series of moiré metasurfaces by MNSL. Due to the variety of gradient plasmonic nanostructures in arrays, single moiré metasurfaces can support multiple localized surface plasmon (LSP) modes with a wide range of resonant wavelengths from ∼600 nm to ∼4200 nm. We analyze the origin of the LSP modes based on the optical spectra and near-field electromagnetic distributions. In addition, we fabricate and analyze the metasurfaces with high-density nanogap structures. These nanogap structures support plasmonic gap modes with significant field enhancements. With their tunable multiband optical responses from visible to near-infrared to mid-infrared regimes, these moiré metasurfaces are applicable for ultrabroadband absorbers, multiband surface-enhanced infrared and Raman spectroscopy, and broadband single-molecule spectroscopy.
authors.affiliation: Department of Mechanical Engineering, Materials Science and Engineering Program, and Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA. zheng@austin.utexas.edu.
authors.forename: Zilong
authors.initials: Z
authors.lastname: Wu
authors.affiliation: International Center for Material Nanoarchitectonics (MANA), National Institute for Materials Science, Tsukuba, 305-0044, Japan. Nagao.Tadaaki@nims.go.jp and CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan.
authors.forename: Kai
authors.initials: K
authors.lastname: Chen
authors.affiliation: Department of Mechanical Engineering, Materials Science and Engineering Program, and Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA. zheng@austin.utexas.edu.
authors.forename: Ryan
authors.initials: R
authors.lastname: Menz
authors.affiliation: International Center for Material Nanoarchitectonics (MANA), National Institute for Materials Science, Tsukuba, 305-0044, Japan. Nagao.Tadaaki@nims.go.jp and CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan.
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Nagao
authors.affiliation: Department of Mechanical Engineering, Materials Science and Engineering Program, and Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA. zheng@austin.utexas.edu.
authors.forename: Yuebing
authors.initials: Y
authors.lastname: Zheng