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Chirp-control of resonant high-order harmonic generation in indium ablation plumes driven by intense few-cycle laser pulses

Research output: Contribution to journalArticlepeer-review

Z. Abdelrahman, M. A. Khokhlova, D. J. Walke, T. Witting, A. Zair, V. V. Strelkov, J. P. Marangos, J. W.G. Tisch

Original languageEnglish
Pages (from-to)15745-15758
Number of pages14
Issue number12
Early online date7 Jun 2018
Accepted/In press7 May 2018
E-pub ahead of print7 Jun 2018
Published11 Jun 2018


King's Authors


We have studied high-order harmonic generation (HHG) in an indium ablation plume driven by intense few-cycle laser pulses centered at 775 nm as a function of the frequency chirp of the laser pulse. We found experimentally that resonant emission lines between 19.7 eV and 22.3 eV (close to the 13th and 15th harmonic of the laser) exhibit a strong, asymmetric chirp dependence, with pronounced intensity modulations. The chirp dependence is reproduced by our numerical time-dependent Schrodinger equation simulations of a resonant HHG by the model indium ion. As demonstrated with our separate simulations of HHG within the strong field approximation, the resonance can be understood in terms of the chirp-dependent HHG photon energy coinciding with the energy of an autoionizing state to ground state transition with high oscillator strength. This supports the validity of the general theory of resonant four-step HHG in the few-cycle limit.

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