Soft X-ray harmonic comb from relativistic electron spikes

A.S. Pirozkhov, M. Kando, Esirkepov T. Zh, P. Gallegos, Hamad Ahmed, E.N. Ragozin, Faenov A. Ya, T.A. Pikuz, T. Kawachi, A. Sagisaka, J.K. Koga, M. Coury, J. Green, P.F. Foster, C. Brenner, Brendan Dromey, D.R. Symes, M. Mori, K. Kawase, T. KameshimaY. Fukuda, L. Chen, I. Daito, K. Ogura, Y. Hayashi, H. Kotaki, H. Kiriyama, H. Okada, N. Nishimori, T. Imazono, K. Kondo, T. Kimura, T. Tajima, H. Daido, P. Rajeev, P. McKenna, Marco Borghesi, D. Neely, Y. Kato, S.V. Bulanov

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We demonstrate a new high-order harmonic generation mechanism reaching the "water window" spectral region in experiments with multiterawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving mu J/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations.
Original languageEnglish
Article number135004
Number of pages5
JournalPhysical Review Letters
Issue number13
Publication statusPublished - 30 Mar 2012

ASJC Scopus subject areas

  • General Physics and Astronomy


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