The development of attosecond pulses across different photon energies is an essential precursor to performing pump-probe attosecond experiments in complex systems, where the potential of attosecond science 1 can be further developed 2,3 . We report the generation and characterization of synchronised XUV (90 eV) and VUV (20 eV) pulses generated simultaneously via high harmonic generation. The VUV pulses are well suited for pump-probe experiments that exploit the high photoionisation cross-section of many molecules in this spectral region 4 , and the higher photon flux due to the higher conversion efficiency of the high harmonics generation process at these energies 5 . We temporally characterised all pulses using the attosecond streaking technique 6 and the FROG-CRAB retrieval method 7 . We report 57616 as pulses at 20 eV and 25721 as pulses at 90 eV. Our demonstration of synchronised attosecond pulses at different photon energies, and inherently jitter-free due to the common-path geometry implemented, offers unprecedented possibilities for pump-probe studies.The production of isolated attosecond pulses (IAP) in the extreme ultraviolet (XUV) region (30-150 eV) with an intense near-infrared (NIR) femtosecond laser is nowadays a robust process. The generation of IAP via high harmonic generation 1 (HHG) requires temporally gating the high harmonics emission to a single burst by using one of several techniques. Most common are polarization gating 8 , double optical gating 9 , ionization gating 10 and amplitude gating 11 . However, the

Attosecond light pulses within the vacuum ultraviolet (VUV) energy range are predicted by solving the time-dependent Schrödinger equation (TDSE) for a model neon atom in short laser pulses of different field polarization states. We compare high-order harmonic generation in linearly polarized laser pulses to the method of polarization gating and find attosecond pulses that approach the Fourier limit of 700 as given by an indium filter, spectrally centered at 15 eV. At such low energies, harmonic generation has low sensitivity to ellipticity, which enables the generation of elliptically polarized attosecond pulses. We also show that emission at the atomic transition energies is strongly damped by including intensity averaging.

Abstract:We demonstrate a novel, single-shot ultrafast diagnostic, based on the dispersionscan (d-scan) technique. In this implementation, rather than scanning wedges to vary the dispersion as in standard d-scan, the pulse to be measured experiences a spatially varying amount of dispersion in a Littrow prism. The resulting beam is then imaged into a secondharmonic generation crystal and an imaging spectrometer is used to measure the twodimensional trace, which is analyzed using the d-scan retrieval algorithm. We compare the single-shot implementation with the standard d-scan for the measurement of sub-3.5-fs pulses from a hollow core fiber pulse compressor. We show that the retrieval algorithm used to extract amplitude and phase of the pulse provides comparable results, proving the validity of the new single-shot implementation down to near single-cycle durations.

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The response of solids to electromagnetic fields is of crucial importance in many areas of science and technology. Many fundamental questions remain to be answered about the dynamics of the photoexcited electrons that underpin this response, which can evolve on timescales of tens to hundreds of attoseconds. How, for example, is the photoexcited electron affected by the periodic potential as it travels in the solid, and how do the other electrons respond in these strongly correlated systems? Furthermore, control of electronic motion in solids with attosecond precision would pave the way for the development of ultrafast optoelectronics. Attosecond electron dynamics can be traced using streaking, a technique where a strong near-infrared laser field accelerates an attosecond electron wavepacket photoemitted by an extreme ultraviolet light pulse, imprinting timing information onto it. We present attosecond streaking measurements on the wide-bandgap semiconductor tungsten trioxide, and on gold, a metal used in many nanoplasmonic devices. Information about electronic motion in the solid is encoded on the temporal properties of the photoemitted electron wavepackets, which are consistent with a spread of electron transport times to the surface following photoexcitation.