Chair: Stephen R. Leone, University of California, Berkeley, USA

  • Oren Cohen
  • Benoit Mahieu
  • Baptiste Fabre
  • Francois Mauger
  • Vincent Gruson

#39, 8:30 – 9:00 Generation of bright high-order harmonics with tunable polarization:Towards helically-polarized attosecond pulses, A. FLEISCHER, O. KFIR, T. DISKIN, P. SIDORENKO, E. BORDO, O. COHEN, P. GRYCHTOL, E. TURGUT, R. KNUT, D. ZUSIN, D. POPMINTCHEV, T. POPMINTCHEV, H. NEMBACH, J. SHAW, H. KAPTEYN AND M. MURNANE, Generation and application of bright phase-matched high-order harmonic with fully tunable polarization – from linear through elliptic to circular – are demonstrated experimentally. An accessible path towards generation of helically polarized attosecond pulses is presented.

#40, 9:00 – 9:15 Control of the ellipticity of high harmonics generated in a two-colour scheme, B. MAHIEU, G. LAMBERT, G. DE NINNO, D. GAUTHIER, C. SPEZZANI, A. ANDREEV, S. STREMOUKHOV, M. FAJARDO, C. P. HAURI, P. SALIÈRES, V. MALKA, B. VODUNGBO AND P. ZEITOUN, We study the control of the ellipticity of high harmonics generated in gas, driven by a two-colour laser field. Our pioneer work demonstrated the possibility to generate elliptically-polarized harmonics using linearly polarized driving fields [1]. Exploiting a Mach-Zehnder configuration, we go here a step further, mainly by changing the crossing angle of the driving fields’ linear polarizations. For values higher than 45°, a significant ellipticity (around 50%) is obtained for both odd and even harmonics. Furthermore, we show the possibility to modify the polarization axis of the individual harmonics. These measurements allow envisaging a full polarization control of harmonics and a better understanding of the generation process.

#41, 9:15 – 9:30 Towards Attosecond XUV Circular Dichroism, A. FERRÉ, C. HANDSCHIN, M. DUMERGUE, F. BURGY, A. COMBY, D. DESCAMPS, B. FABRE, G.A. GARCIA, R. GÉNEAUX, L. MERCERON, E. MÉVEL, L. NAHON, S. PETIT, B. PONS, D. STAEDTER, S. WEBER, T. RUCHON, V. BLANCHET AND Y. MAIRESSE, XUV circular dichroism is based on the asymmetric response of a target interacting with chiral light. Due to its differential character, this technique is a very sensitive and powerful tool to study structural properties of matter, from the photoionization of chiral systems to the magnetic properties of solids. However, extension of this technique, on synchrotron or free electron lasers, to dynamical studies is not straightforward. We present here a table-top and competitive alternative source based on high harmonic generation which delivers quasi-circular pulses in the extreme ultraviolet range.

#42, 9:30 – 9:45 High Harmonic Generation and Polarization: Angular Momentum Conservation vs Discrete Time-Dependent Symmetries, F. MAUGER, A.D. BANDRAUK AND T. UZER, We discuss the place of angular momentum conservation in theoretical and numerical models for high harmonic generation (HHG). Recent experimental work [A. Fleischer et al., Nature Photonics 8, 543 (2014)] has shown conflicting results regarding the conservation of the (photon) angular momentum in HHG. We show that simulations using classical fields do not conserve angular momentum and that the properties of HHG spectra are actually due to more general discrete time-dependent symmetries that apply equally well for atoms and molecules and we propose a configuration to test for the accuracy of simulations compared to selection rule predictions.

#43, 9:45 – 10:00 Depolarization in High Harmonic Generation, KEVIN VEYRINAS, VINCENT GRUSON, S. J. WEBER, L. BARREAU, T. RUCHON, J.C. HOUVER, B. CARRÉ, R.R. LUCCHESE, D. DOWEK AND P. SALIÈRES, We perform the first complete characterization of high harmonic polarization state including helicity and degree of polarization using molecular polarimetry, based on the analysis of the Molecular Frame Photoelectron Angular Distribution (MFPAD) in molecular dissociative photoionization. We study the elliptical XUV emission produced using three types of symmetry breaking: SF6 molecules irradiated by elliptically polarized laser, Argon atoms irradiated by counterrotating bichromatic fields, and N2 molecules aligned with respect to a linear driving field. Our results are compared to the incomplete optical polarimetry measurements performed up to now, revealing, e.g., in N2 , a much smaller ellipticity and significant depolarization.


Chair: Katsumi Midorikawa, Riken, Tokyo, Japan

  • Juergen Schmidt
  • Peng He
  • Cheng Jin
  • Gilad Marcus
  • Ashiq Fareed

#44, 10:30 ­­- 10:45 Generation of circularly polarized high harmonic radiation using a transmission multilayer quarter waveplate, J. SCHMIDT, A. GUGGENMOS, S.H. CHEW, M. HOFSTETTER AND U. KLEINEBERG, We produced a multilayer based transmission EUV quarter waveplate in order to transform linearly polarized high harmonic (HH) radiation into circular polarization. Our waveplate is designed for a nominal photon energy of 66 eV and the polarization state is analyzed using a broadband multilayer polarizer with a bandwidth of 4.6 eV FWHM, supporting 400 asec high harmonic pulses. We measured a broadband ellipticity of 75% with a transmission efficiency of 5%. The helicity is switchable by changing the azimuthal alignment angle of the waveplate. As small, single element it can be easily integrated in any existing harmonic beamline without major changes.

#45, 10:45 – 11:00 Temporal and spatial characterization of HHG source driven by CEP-stablized sub-2-cycle laser pulses, PENG HE, HAO TENG, XINKUI HE, PENG YE, MINJIE ZHAN, LIFENG WANG, AND ZHIYI WEI, An attosecond beamline which delivers sub-200-as at 83 eV was developed. Temporal and spatial characterization of HHG driven by sub-5-fs are investigated based on this attosecond beamline. Due to the truncated Bessel beam from hollow fiber, the divergence of generated harmonic can be controlled by moving the location of gas cell, and minimized angular divergence can be obtained. From the two-dimensional spectrum with resolution of temporal frequency and spatial frequency, a full quantum trajectory resolved harmonic spectrum is analysized.

#46, 11:00 – 11:15 Efficient generation of low divergent soft X-ray high harmonics in a hollow waveguide using two-color optimized laser pulses, CHENG JIN, GREGORY J. STEIN, KYUNG-HAN HONG, AND C. D. LIN, We apply a two-color optimized waveform into a gas-filled hollow waveguide to efficiently generate lowdivergence high-order harmonics. The drive waveform is previously optimized such that single-atom highest harmonic yields are emitted from the recombination of “short”-trajectory electrons with the atomic ions. To obtain intense and spatially coherent harmonics extending from the extreme ultraviolet to soft X-rays, gas pressure and waveguide configuration are optimized, to achieve good phase matching and to maintain the waveform inside the waveguide. The physics behind is the interplay of the dispersion due to waveguide mode, atomic dispersion and plasma effect. + Hollow waveguide, waveform, phase matching.

#47, 11:15 – 11:30 The role of phase matching in resonant high harmonics generation, NOA ROSENTHAL, AND GILAD MARCUS, Resonance high order harmonic is an exciting phenomenon, predicted long time ago, but discovered only recently. Explanations for the resonance enhancement of a single harmonic rely either on the single atom response or on the collective process of phase matching. In this work we try to discriminate between the two possibilities by measuring the coherent length of all the harmonics and compare them. Having the coherent lengths of the harmonics, allow us also to demonstrate quasi phase matching enhancement of the harmonics yield.

#48, 11:30 – 11:45 Variation of Redshift in High-order Harmonics Generated from Laser Ablated Carbon Molecules using Various Laser Wavelengths, M. A. FAREED, XUE-BIN BIAN, N. THIRÉ, S. MONDAL, Y. PERTOT, B. E. SCHMIDT, A. D. BANDRAUK, F. LÉGARÉ, AND T. OZAKI, We study the redshift in high-order harmonics generated from laser ablated carbon molecules, for several driving laser wavelengths at 400 nm, 800 nm, 1410 nm and 1710 nm. Results show that a maximum redshift of 2.3 nm is observed with 800 nm laser at 17 eV. This redshift reduces to 0.5 nm at 1410 nm and then disappears completely for 1710 nm lasers. However, for 400 nm lasers, we have observed a blue shift at high laser intensities, rather than a redshift.


Chair Richard Taïeb, U. Pierre et Marie Curie, Paris, France

#49, 12:00 – 12:30 Attosecond clocking of electron collisions in dielectric nanoparticles, M. F. KLING, F. CALEGARI, S. ZHEREBTSOV, Q. LIU, P. RUPP, L. SEIFFERT, A. TRABATTONI, M. CASTROVILLI, S. ANUMULA, F. SÜßMANN, K. WINTERSPERGER, J. STIERLE, G. SANSONE, L. POLETTO, F. FRASSETTO, V. MONDES, C. GRAF, E. RÜHL, F. KRAUSZ, M. NISOLI, AND T. FENNEL, We investigated electron dynamics following ionization by an attosecond pulse at 35 eV in dielectric nanoparticles using attosecond streaking spectroscopy. Single-shot velocity-map imaging permits to identify laser shots with and without nanoparticles. The time delay between the respective streaking traces of ~100 as is interpreted by scattering theory indicating that the measurements permit to clock the inelastic electron scattering time.

#50, 12:30 – 12:45 Attosecond Near-Field Streaking from Metal Nanotips, B. FÖRG, J. SCHÖTZ, F. SÜßMANN, M. FÖRSTER, M. KRÜGER, B. AHN, K. WINTERSPERGER, S.ZHEREBTSOV, A. GUGGENMOS, V. PERVAK, A. KESSEL, S. A. TRUSHIN, A. M. AZZEER, M. I. STOCKMAN, D. KIM, F. KRAUSZ, P. HOMMELHOFF, AND M.F. KLING, The vision of attosecond temporal and nanoscale spatial resolution for the investigation of collective electron motion gave birth to the new research field of attosecond nanophysics. One major goal is the complete characterization of nanoscale optical fields with sub-cycle temporal resolution. We report on achieving this goal by the experimental implementation of attosecond near-field streaking. By comparing streaking traces from gold nanotips to a reference from a noble gas, we show that the spectral response of the nanotip near-field arising from intense laser excitation can be extracted. Monte-Carlo (MC) trajectory simulations in near-fields calculated using the macroscopic Maxwell’s equations support our experimental findings.

#51, 12:45 – 13:00 Intense supercontinuum and few – cycle pulses generated in condensed media, CHIH-HSUAN LU, BO-HAN CHEN, HONG-YU CHEN, YU-JUNG TSOU, YU-CHEN CHENG, PEI-CHI HUANG, SHANG-DA YANG,  MING-CHANG CHEN, AND A. H. KUNG, We overcame the large material dispersion and avoided optical damage to generate an intense octave-spanning supercontinuum in a solid medium that could be compressed to produce fewcycle pulses with multi-GW peak power and demonstrated high harmonic generation using these pulses.

#52, 13:00 – 13:15 Extreme ultraviolet coherence tomography with high harmonic generation light sources, S. FUCHS, J. BIEDERMANN, M. WÜNSCHE, J. BERNERT, C. RÖDEL, M. MÖLLER, AND G. G. PAULUS, We present a novel method for cross sectional imaging with nanometer resolution which is referred to as XUV coherence tomography (XCT). XCT uses extreme ultra violet light (XUV), e.g., from high harmonic generation (HHG).  In XCT, the coherence length of few nanometers of broadband XUV sources is exploited. Thus, XCT extends optical coherence tomography (OCT) by improving the axial resolution from micrometers to nanometers. In a first step, we demonstrated XCT at synchrotron sources, successfully. Here, we present first results of XCT with High Harmonic Generation sources.