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.