High-order harmonic generation of pulses with multiple timescales: selection rules, carrier envelope phase and cutoff energy

Ofer Neufeld*, Avner Fleischer, Oren Cohen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

High harmonic generation (HHG) is sensitive to the carrier envelope phase (CEP) of its driving laser field if it is a sufficiently short pulse (several-cycle pulse). Here we show that strong CEP effects can also be found in HHG from long duration multi-cycle pulses (up to 200 fs at 800 nm central wavelength). We find that HHG from multi-cycle pulses may be CEP dependent when the driving pulse exhibits two distinct timescales (multi-timescale pulse): (i) a short timescale associated with the average frequency, and (ii) a long timescale associated with the pulse’s temporal periodicity. The interplay of these timescales results in significant changes to both the cutoff frequency, and the appearance of symmetry allowed harmonics in the spectrum as function of CEP, similar to HHG from several-cycle pulses. We relate this effect to the multi-timescale intensity variations in the driving pulse, and construct an analytical condition to access the phenomenon. Lastly, we numerically demonstrate reconstruction of the CEP through HHG from long duration multi-timescale pulses. Our work may be useful in several areas of strong-field physics and attosecond science, for example, allowing spectroscopy of multi-timescale processes (e.g. HHG from vibrationally active media), and paving the way towards CEP characterisation using long pulses.

Original languageEnglish
Pages (from-to)1956-1963
Number of pages8
JournalMolecular Physics
Volume117
Issue number15-16
DOIs
StatePublished - 18 Aug 2019
Externally publishedYes

Keywords

  • High harmonic generation
  • carrier-envelope phase
  • dynamical symmetry

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