title: Broadband terahertz generation from metamaterials.
abstract: The terahertz spectral regime, ranging from about 0.1-15 THz, is one of the least explored yet most technologically transformative spectral regions. One current challenge is to develop efficient and compact terahertz emitters/detectors with a broadband and gapless spectrum that can be tailored for various pump photon energies. Here we demonstrate efficient single-cycle broadband THz generation, ranging from about 0.1-4 THz, from a thin layer of split-ring resonators with few tens of nanometers thickness by pumping at the telecommunications wavelength of 1.5 μm (200 THz). The terahertz emission arises from exciting the magnetic-dipole resonance of the split-ring resonators and quickly decreases under off-resonance pumping. This, together with pump polarization dependence and power scaling of the terahertz emission, identifies the role of optically induced nonlinear currents in split-ring resonators. We also reveal a giant sheet nonlinear susceptibility ~10(-16) m(2) V(-1) that far exceeds thin films and bulk non-centrosymmetric materials.
authors.affiliation: Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Luo
authors.affiliation: 1] Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA [2].
authors.forename: Ioannis
authors.initials: I
authors.lastname: Chatzakis
authors.affiliation: Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Jigang
authors.initials: J
authors.lastname: Wang
authors.affiliation: Institute of Applied Physics, Institute of Nanotechnology and DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany.
authors.forename: Fabian B P
authors.initials: FB
authors.lastname: Niesler
authors.affiliation: Institute of Applied Physics, Institute of Nanotechnology and DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wegener
authors.affiliation: Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Koschny
authors.affiliation: 1] Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA [2] Institute of Electronic Structure and Lasers (IESL), FORTH, 71110 Heraklion, Crete, Greece.
authors.forename: Costas M
authors.initials: CM
authors.lastname: Soukoulis