title: Extremely Nonperturbative Nonlinearities in GaAs Driven by Atomically Strong Terahertz Fields in Gold Metamaterials.
abstract: Terahertz near fields of gold metamaterials resonant at a frequency of 0.88 THz allow us to enter an extreme limit of nonperturbative ultrafast terahertz electronics: Fields reaching a ponderomotive energy in the keV range are exploited to drive nondestructive, quasistatic interband tunneling and impact ionization in undoped bulk GaAs, injecting electron-hole plasmas with densities in excess of 10^{19}  cm^{-3}. This process causes bright luminescence at energies up to 0.5 eV above the band gap and induces a complete switch-off of the metamaterial resonance accompanied by self-amplitude-modulation of transmitted few-cycle terahertz transients. Our results pave the way towards highly nonlinear terahertz optics and optoelectronic nanocircuitry with subpicosecond switching times.
authors.affiliation: Department of Physics, University of Regensburg, 93040 Regensburg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Lange
authors.affiliation: Department of Physics, University of Regensburg, 93040 Regensburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Maag
authors.affiliation: Department of Physics, University of Regensburg, 93040 Regensburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Hohenleutner
authors.affiliation: Department of Physics, University of Regensburg, 93040 Regensburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Baierl
authors.affiliation: Department of Physics, University of Regensburg, 93040 Regensburg, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Schubert
authors.affiliation: Department of Physics, Martin-Luther-University Halle-Wittenberg, 06120 Halle, Germany.
authors.forename: E R J
authors.initials: ER
authors.lastname: Edwards
authors.affiliation: Department of Physics, University of Regensburg, 93040 Regensburg, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Bougeard
authors.affiliation: Department of Physics, Martin-Luther-University Halle-Wittenberg, 06120 Halle, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Woltersdorf
authors.affiliation: Department of Physics, University of Regensburg, 93040 Regensburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Huber