title: Realization of mid-infrared graphene hyperbolic metamaterials.
abstract: While metal is the most common conducting constituent element in the fabrication of metamaterials, graphene provides another useful building block, that is, a truly two-dimensional conducting sheet whose conductivity can be controlled by doping. Here we report the experimental realization of a multilayer structure of alternating graphene and Al2O3 layers, a structure similar to the metal-dielectric multilayers commonly used in creating visible wavelength hyperbolic metamaterials. Chemical vapour deposited graphene rather than exfoliated or epitaxial graphene is used, because layer transfer methods are easily applied in fabrication. We employ a method of doping to increase the layer conductivity, and our analysis shows that the doped chemical vapour deposited graphene has good optical properties in the mid-infrared range. We therefore design the metamaterial for mid-infrared operation; our characterization with an infrared ellipsometer demonstrates that the metamaterial experiences an optical topological transition from elliptic to hyperbolic dispersion at a wavelength of 4.5 μm.
authors: Center for Photonics and Multiscale Nanomaterials, University of Michigan, 2200 Bonisteel Blvd., Ann Arbor, Michigan 48109, USA.|Department of Physics, University of Michigan, 450 Church St, Ann Arbor, Michigan 48109, USA.
authors: You-Chia
authors: YC
authors: Chang
authors: Center for Photonics and Multiscale Nanomaterials, University of Michigan, 2200 Bonisteel Blvd., Ann Arbor, Michigan 48109, USA.|Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109, USA.
authors: Che-Hung
authors: CH
authors: Liu
authors: Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109, USA.
authors: Chang-Hua
authors: CH
authors: Liu
authors: School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, Geogia 30332, USA.
authors: Siyuan
authors: S
authors: Zhang
authors: School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, Geogia 30332, USA.
authors: Seth R
authors: SR
authors: Marder
authors: School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907, USA.
authors: Evgenii E
authors: EE
authors: Narimanov
authors: Center for Photonics and Multiscale Nanomaterials, University of Michigan, 2200 Bonisteel Blvd., Ann Arbor, Michigan 48109, USA.|Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109, USA.
authors: Zhaohui
authors: Z
authors: Zhong
authors: Center for Photonics and Multiscale Nanomaterials, University of Michigan, 2200 Bonisteel Blvd., Ann Arbor, Michigan 48109, USA.|Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109, USA.
authors: Theodore B
authors: TB
authors: Norris