3 research outputs found
Enhanced multi-colour gating for the generation of high-power isolated attosecond pulses
Isolated attosecond pulses (IAP) generated by high-order harmonic generation
are valuable tools that enable dynamics to be studied on the attosecond time
scale. The applicability of these IAP would be widened drastically by
increasing their energy. Here we analyze the potential of using multi-colour
driving pulses for temporally gating the attosecond pulse generation process.
We devise how this approach can enable the generation of IAP with the available
high-energy kHz-repetition-rate Ytterbium-based laser amplifiers (delivering
180-fs, 1030-nm pulses). We show theoretically that this requires a
three-colour field composed of the fundamental and its second harmonic as well
as a lower-frequency auxiliary component. We present pulse characterization
measurements of such auxiliary pulses generated directly by white-light seeded
OPA with the required significantly shorter pulse duration than the that of the
fundamental. This, combined with our recent experimental results on
three-colour waveform synthesis [Phys. Rev. X 4, 021028 (2014)], proves that
the theoretically considered multi-colour drivers for IAP generation can be
realized with existing high-power laser technology. The high-energy driver
pulses, combined with the strongly enhanced single-atom-level conversion
efficiency we observe in our calculations, thus make multi-colour drivers prime
candidates for the development of unprecedented high-energy IAP sources in the
near future
Near- and Extended-Edge X-Ray-Absorption Fine-Structure Spectroscopy Using Ultrafast Coherent High-Order Harmonic Supercontinua
Recent advances in high-order harmonic generation have made it possible to use a tabletop-scale setup to produce spatially and temporally coherent beams of light with bandwidth spanning 12 octaves, from the ultraviolet up to x-ray photon energies >1.6  keV. Here we demonstrate the use of this light for x-ray-absorption spectroscopy at the K- and L-absorption edges of solids at photon energies near 1 keV. We also report x-ray-absorption spectroscopy in the water window spectral region (284-543 eV) using a high flux high-order harmonic generation x-ray supercontinuum with 10^{9}  photons/s in 1% bandwidth, 3 orders of magnitude larger than has previously been possible using tabletop sources. Since this x-ray radiation emerges as a single attosecond-to-femtosecond pulse with peak brightness exceeding 10^{26}  photons/s/mrad^{2}/mm^{2}/1% bandwidth, these novel coherent x-ray sources are ideal for probing the fastest molecular and materials processes on femtosecond-to-attosecond time scales and picometer length scales.093002
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Near- and Extended-Edge X-Ray-Absorption Fine-Structure Spectroscopy Using Ultrafast Coherent High-Order Harmonic Supercontinua.
Recent advances in high-order harmonic generation have made it possible to use a tabletop-scale setup to produce spatially and temporally coherent beams of light with bandwidth spanning 12 octaves, from the ultraviolet up to x-ray photon energies >1.6  keV. Here we demonstrate the use of this light for x-ray-absorption spectroscopy at the K- and L-absorption edges of solids at photon energies near 1 keV. We also report x-ray-absorption spectroscopy in the water window spectral region (284-543 eV) using a high flux high-order harmonic generation x-ray supercontinuum with 10^{9}  photons/s in 1% bandwidth, 3 orders of magnitude larger than has previously been possible using tabletop sources. Since this x-ray radiation emerges as a single attosecond-to-femtosecond pulse with peak brightness exceeding 10^{26}  photons/s/mrad^{2}/mm^{2}/1% bandwidth, these novel coherent x-ray sources are ideal for probing the fastest molecular and materials processes on femtosecond-to-attosecond time scales and picometer length scales