Generation of extreme ultraviolet continuum radiation driven by a sub-10-fs two-color field.
ABSTRACT We have proposed and demonstrated a novel approach for generating high-energy extreme-ultraviolet (XUV) continuum radiation. When a two-color laser field consisting of a sub-10-fs fundamental and its parallel-polarized second harmonic was applied to high-order harmonic generation in argon, a continuum spectrum centered at 30 nm was successfully obtained with an energy as high as 10 nJ. This broadband emission indicates the possibility of generating intense single attosecond pulses in the XUV region.
Full-textDOI: · Available from: Fumihiko Kannari, Sep 26, 2014
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ABSTRACT: High-order harmonic emission can be confined to the leading edge of an 800 nm driver laser pulse under moderately intense focusing conditions (7×10^14 W/cm^2) (Pfeifer et al. in Opt. Express 15:17120, 2007). Here, the experimentally observed curtailment of harmonic production on the leading edge of the driver pulse is shown to be controlled by an ionization-induced phase-matching condition. The transient plasma density inherent to the process of high-harmonic generation terminates the harmonic emission by an ultrafast loss of phase matching on the leading edge of the laser pulse. The analysis is supported by a reconstruction of the in situ intensity envelope of the driver pulse with attosecond temporal resolution, performed by measurements of the carrier-envelope phase dependence of individual half-cycle harmonic cutoffs. The method opens the way to wavelength-tunable isolated attosecond pulse generation.Applied Physics B 11/2008; 93(2-3). DOI:10.1007/s00340-008-3187-z · 1.63 Impact Factor
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ABSTRACT: We numerically calculate the high-order harmonic generation (HHG) power spectra from a one-dimensional model atom irradiated by linearly polarised 12fs two-colour laser pulses composed of a fundamental pulse from Ti:sapphire laser and its second harmonic. It is found that a distinct double plateau structure appears when the relative phase of the two pulses is set as π/8, 2π/8 or 3π/8, and the double plateau structure disappears when the relative phase is set as 4π/8, 5π/8, 6π/8 or 7π/8. The relative-phase-dependent plateau structure is explained by the temporal profile of the synthesised electric fields as well as the semi-classical “three-step” model. Moreover, our numerical result shows that cut-off frequencies of the two-colour pulse HHG spectra can be exactly predicted by use of the semi-classical “three-step” model.The European Physical Journal D 03/2010; 57(1):145-149. DOI:10.1140/epjd/e2009-00325-0 · 1.40 Impact Factor
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ABSTRACT: We propose a method to generate a single-attosecond soft-x-ray or extreme ultraviolet pulse by use of two infrared (IR) laser pulses of different wavelengths, neither of which alone is sufficiently short for single-pulse generation. Our simulations based on the time-dependent Schroedinger equation show that, when a harmonic pulse train generated by one IR laser field is superposed with the other driving laser and applied to a target atom, only one pulse in the train significantly boosts harmonic generation and acts as an attosecond enhancement gate for isolated pulse generation.Physical Review A 02/2007; 75(2). DOI:10.1103/PHYSREVA.75.021801 · 2.99 Impact Factor