Efficient Extreme UV Harmonics Generated from Picosecond Laser Pulse Interactions with Solid Targets

Norreys, P. A.; Zepf, Matthew; Moustaizis, S.; Fews, AP; Zhang, Jianjun; Lee, Paul; Bakarezos, Makis; Danson, C.; Dyson, A.; Gibbon, Paul; Loukakos, P. A.; Neely, D.; Walsh, F.; Wark, J. S.; Dangor, A. E.

doi:10.1103/physrevlett.76.1832

Cited by 315 publications

(165 citation statements)

References 26 publications

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“…Therefore, the field cannot be thought of as a small perturbation to the crystal. The non-perturbative HHG from bulk crystals has been considered theoretically 12-14 but has never been observed experimentally until now.Previously, experimental observation of non-perturbative HHG in solids was only in reflection geometry [15][16][17][18] perturbative harmonics below the band edge up to the seventh order were produced by exciting semiconducting ZnSe with a maximum field strength of ∼0.08 V Å −1 at a central wavelength of 3.9 µm (ref. 19).…”

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confidence: 99%

Observation of high-order harmonic generation in a bulk crystal

et al. 2010

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Harmonic generation is a general feature of driven nonlinear systems. In particular high-order harmonic generation (HHG) in atomic gases 1 is the basis for producing attosecond pulses 2,3 . In molecules and clusters, the existence of multiple ionization and recombination sites makes for richer dynamics allowing imaging of molecular orbitals 4,5 , higher conversion efficiency 6 and the possibility of extending the high-energy cutoff 7 . In the strong-field limit, HHG in bulk crystals is fundamentally different from that in the atomic case owing to the high density and periodic structure. Here we present the first observation of HHG in a bulk crystalline solid using a long-wavelength few-cycle laser. The harmonics spectra extend well beyond the band edge of the ZnO crystal, show a clear non-perturbative character and exhibit a cutoff that scales linearly with the electric field of the drive laser. Our results have important implications for the understanding of attosecond electron dynamics and other non-equilibrium band-structure-related phenomena in strongly driven bulk solids.The HHG spectrum from a gas typically comprises a region of rapidly decreasing low orders that scale perturbatively followed by a slowly varying succession of higher orders that scale nonperturbatively with the strength of the drive laser 1 . At the tunnelling limit of strong-field ionization 8 , the non-perturbative harmonic generation process has been described semiclassically in a recollision model 9,10 consisting of three steps: tunnel ionization of an electron, its acceleration in the laser field, and its recombination to the parent ion with an energy release in the form of higher-energy photons-a coherent process that occurs on successive half-cycles of the laser pulse, leading to emission of odd harmonics. The single-atom maximum photon energy is 9,11h ω max = I p + 3.2U p , where I p is the ionization potential and U p = e 2 E 2 λ 2 /16π 2 mc 2 is the ponderomotive energy of the electron in the laser field. The amplitude of the maximum excursion of a recolliding electron is r max = eEλ 2 /4π 2 mc 2 . For the conditions of our experiments, E = 0.6 V Å −1 at λ = 3.25 µm, the atomic case would be U p = 5 eV and r max = 32 Å. The latter is many times the lattice constant of a typical crystal. Thus, we expect the possibility of ionization from one site and recombination on another; however, because of the lattice periodicity the process would still be coherent. We note that at this field strength, the potential across a lattice constant is comparable to the bandgap of a typical insulator. Therefore, the field cannot be thought of as a small perturbation to the crystal. The non-perturbative HHG from bulk crystals has been considered theoretically 12-14 but has never been observed experimentally until now.Previously, experimental observation of non-perturbative HHG in solids was only in reflection geometry [15][16][17][18] perturbative harmonics below the band edge up to the seventh order were produced by exciting semiconducting ZnSe with...

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Observation of high-order harmonic generation in a bulk crystal

et al. 2010

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“…It is therefore essential that the efficiency measurement is accompanied by a simultaneous determination of the beam divergence. In the past, a number of efficiency measurements mainly for individual harmonics and for different spectral ranges have been reported [13,18,21,[24][25][26]. The solid angle of the emission in these reports was mostly estimated without concurrent determination of the actual emission cone.…”

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confidence: 99%

“…The reason is the commonly large solid angle of the emission due to tight laser beam focusing compared to the pencil-like XUV beam produced by the gas targets. More importantly, instabilities occurring at the plasma-vacuum interface can cause rippling of the critical surface resulting in the scattering of the emission into a large solid angle up to 2π [21][22][23]. The generation of ROM harmonics with divergence corresponding to the harmonic wavelength, i.e., less than the original laser beam was accomplished only since the availability of high-contrast ultrashort laser pulses using double plasma mirrors [17].…”

Section: Introductionmentioning

confidence: 99%

Multi-μJ harmonic emission energy from laser-driven plasma

et al. 2014

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“…A similar transition is found for increasing field strength in high-harmonic generation in laser-irradiated foils. The 'oscillating mirror model' of laser-foil interactions has been used to predict different power-law exponents γ , for example γ = −5/2 (Gordienko et al 2004) and γ = −8/3 (Baeva, Gordienko & Pukhov 2006) have been postulated, and experiments on solid targets have recorded intensity-dependent power-law exponents, for example in Norreys et al (1996) of −5.50 < γ < −3.38.…”

Section: Discussionmentioning

confidence: 99%

Vacuum high-harmonic generation and electromagnetic shock

Böhl

King²,

Rühl

2016

J. Plasma Phys.

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When one takes into account the presence of virtual charged states in the quantum vacuum, a nonlinear self-interaction can arise in the propagation of electromagnetic fields. This self-interaction is often referred to as 'real photon-photon scattering'. When the centre-of-mass energy of colliding photons is much lower than the rest energy of an electron-positron pair, this quantum effect can be included in the classical field equations of motion as a vacuum current and charge density using the Heisenberg-Euler Lagrangian. Using analytical and numerical methods for subcritical fields, the intrinsic solution to Maxwell's equations has been found for counterpropagating probe and pump plane waves in the presence of vacuum fourand six-wave mixing. In the corresponding all-order solution for the scattered probe, a route to vacuum high-harmonic generation is identified in which a long phase length can compensate for the weakness of interacting fields. The resulting shocks in the probe carrier wave and envelope are studied for different parameter regimes and polarisation set-ups. In this special issue, we study two additional set-ups: that of a slowly varying single-cycle background to highlight the effect of an oscillating background on the probe harmonic spectrum, and that of a few-cycle probe to highlight the smoothing of the harmonic peaks produced by a wider spectrum of probe photons. We also correct sign errors in an earlier publication.

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Efficient Extreme UV Harmonics Generated from Picosecond Laser Pulse Interactions with Solid Targets

Cited by 315 publications

References 26 publications

Observation of high-order harmonic generation in a bulk crystal

Observation of high-order harmonic generation in a bulk crystal

Multi-μJ harmonic emission energy from laser-driven plasma

Vacuum high-harmonic generation and electromagnetic shock

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