title: Linking high harmonics from gases and solids.
abstract: When intense light interacts with an atomic gas, recollision between an ionizing electron and its parent ion creates high-order harmonics of the fundamental laser frequency. This sub-cycle effect generates coherent soft X-rays and attosecond pulses, and provides a means to image molecular orbitals. Recently, high harmonics have been generated from bulk crystals, but what mechanism dominates the emission remains uncertain. To resolve this issue, we adapt measurement methods from gas-phase research to solid zinc oxide driven by mid-infrared laser fields of 0.25 volts per ångström. We find that when we alter the generation process with a second-harmonic beam, the modified harmonic spectrum bears the signature of a generalized recollision between an electron and its associated hole. In addition, we find that solid-state high harmonics are perturbed by fields so weak that they are present in conventional electronic circuits, thus opening a route to integrate electronics with attosecond and high-harmonic technology. Future experiments will permit the band structure of a solid to be tomographically reconstructed.
authors.affiliation: Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Vampa
authors.affiliation: Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
authors.forename: T J
authors.initials: TJ
authors.lastname: Hammond
authors.affiliation: INRS-EMT, 1650 boulevard Lionel-Boulet, CP 1020, Varennes, Québec J3X 1S2, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Thiré
authors.affiliation: INRS-EMT, 1650 boulevard Lionel-Boulet, CP 1020, Varennes, Québec J3X 1S2, Canada.
authors.forename: B E
authors.initials: BE
authors.lastname: Schmidt
authors.affiliation: INRS-EMT, 1650 boulevard Lionel-Boulet, CP 1020, Varennes, Québec J3X 1S2, Canada.
authors.forename: F
authors.initials: F
authors.lastname: Légaré
authors.affiliation: Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
authors.forename: C R
authors.initials: CR
authors.lastname: McDonald
authors.affiliation: Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Brabec
authors.affiliation: 1] Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada [2] National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada.
authors.forename: P B
authors.initials: PB
authors.lastname: Corkum