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We report here on the experimental pulse duration compression down to sub-20fs of up to 2mJ, 330fs pulses of an 80W Ytterbium laser, using argon-filled multi-pass-cell reproduced by numerical calculations stressing the role of the driver pulse profile.

In the last years, different methods of laser pulse post-compression have proven their efficiency. Nonlinear spectral broadening achieved when coupling an ultrafast pulse in a gas-filled multi-pass-cell (MPC) provides common pulse compression factors of 10 to 20, depending on the initial pulse duration. We report here on the compression of up to 2 mJ, 330 fs pulses of an Ytterbium (Yb) based laser down to sub-20 fs (compression factor of 17), using argon-filled MPCs, at the limit of temporal pulse breakup. Numerical calculations reproducing the experiment data, and demonstrating the importance of the driver pulse profile on the shape of the broadened spectra, are discussed.

Generating high-energy few-cycle pulses is key in the study of light-matter interaction in the regime of high field physics. Attosecond science possess the necessary time resolution to study the underlying fundamental processes but requires repetitions rates on the order the kilohertz and stabilization of the Carrier-Envelope Phase. We present here a post-compression stage delivering 3.8fs pulses with 2.5mJ coupled to a Ti: Sa based 1 kHz TW-class laser which can deliver 17.8fs pulses with 350mrad shot to shot CEP noise. This is the first step towards high-energy few-cycle post-compression of the FAB laser at ATTOLAB-Orme.

High harmonic radiation, produced when intense laser pulses interact with matter, is composed of a train of attosecond pulses. Individual pulses in this train carry information on ultrafast dynamics that vary from one half-optical-cycle to the next. Here, we demonstrate an all-optical photonic streaking measurement that provides direct experimental access to each attosecond pulse by mapping emission time onto propagation angle. This is achieved by inducing an ultrafast rotation of the instantaneous laser wavefront at the focus. We thus time-resolve attosecond pulse train generation, and hence the dynamics in the nonlinear medium itself. We apply photonic streaking to harmonic generation in gases and directly observe, for the first time, the influence of non-adiabatic electron dynamics and plasma formation on the generated attosecond pulse train. These experimental and numerical results also provide the first evidence of the generation of attosecond lighthouses in gases, which constitute ideal sources for attosecond pump-probe spectroscopy. [ABSTRACT FROM AUTHOR]

The present work, performed in the frame of the EXULITE project, was dedicated to the design and characterization of a laser-plasma-produced extreme ultraviolet (EUV) source prototype at 13.5 nm for the next generation lithography. It was conducted in cooperation with two laboratories from CEA, ALCATEL and THALES. One of our approach originalities was the laser scheme modularity. Six Nd:YAG laser beams were focused at the same time on a xenon filament jet to generate the EUV emitting plasma. Multiplexing has important industrial advantages and led to interesting source performances in terms of in-band power, stability and angular emission properties with the filament jet target. A maximum conversion efficiency (CE) value of 0.44% in 2π sr and 2% band-width was measured, which corresponds to a maximum in band EUV mean power of 7.7 W at a repetition rate of 6 kHz. The EUV emission was found to be stable and isotropic in these conditions. [ABSTRACT FROM AUTHOR]

The propagation of an ultrashort laser pulse can be affected by the light reaching the medium before the pulse. This can cause a serious drawback to possible applications. The propagation in He of an intense 60-fs pulse delivered by a Ti:sapphire laser in the chirped pulse amplification (CPA) mode has been investigated in conditions of interest for laser-plasma acceleration of electrons. The effects of both nanosecond amplified spontaneous emission and picosecond pedestals have been clearly identified. There is evidence that such effects are basically of refractive nature and that they are not detrimental for the propagation of a CPA pulse focused to moderately relativistic intensity. The observations are fully consistent with numerical simulations and can contribute to the search of a stable regime for laser acceleration. [ABSTRACT FROM AUTHOR]

A correction to the article "Prepulse effect on intense femtosecond laser pulse propagation in gas" is presented.

High harmonic generation (HHG) has become a core pillar of attosecond science. Traditionally described with field-based models, HHG can also be viewed in a parametric picture, which predicts all properties of the emitted photons, but not the nonperturbative efficiency of the process. Driving HHG with two noncollinear beams and deriving analytically the corresponding yield scaling laws for any intensity ratio, we herein reconcile the two interpretations, introducing a generalized photonic description of HHG. It is in full agreement with field-based simulations and experimental data, opening the route to smart engineering of HHG with multiple driving beams.

Femtosecond laser sources with high repetition rate in the ultraviolet (UV) and vacuum UV (VUV) are fundamental tools enabling tabletop time-resolved and angle-resolved photoemission spectroscopy in solids. We describe a VUV source at 114 nm (10.8 eV) based on an industrial grade ytterbium-doped ultrafast laser, a nonlinear pulse width selection stage, and two cascaded frequency tripling stages, first in crystals, second in xenon. The role of ionization in gas-based perturbative third harmonic generation phase-matching is analyzed using a simple theory, numerical simulations, and experimental data. The source features high photon flux, high repetition rate, and adjustable time resolutions. Thereby, in combination with a state-of-the-art angle-resolved photoemission spectroscopy (ARPES) apparatus it enables the study of the electronic dynamics of the whole Brillouin zone in a large number of materials.

An interesting property of high harmonic generation in solids is its laser polarization dependent nature which in turn provides information about the crystal and band structure of the generation medium. Here we report on the linear polarization dependence of high-order harmonic generation from a gallium arsenide crystal. Interestingly, we observe a significant evolution of the anisotropic response of above bandgap harmonics as a function of the laser intensity. We attribute this change to fundamental microscopic effects of the emission process comprising a competition between intraband and interband dynamics. This intensity dependence of the anisotropic nature of the generation process offers the possibility to drive and control the electron current along preferred directions of the crystal, and could serve as a switching technique in an integrated all-solid-state petahertz optoelectronic device.

In this Letter, we use a 0-π square-wave phase grating to shape 1350 nm and 1450 nm femtosecond pulses and create two intense lobes at the focus of a lens. We show that the relative phase between these two lobes (the 1st and -1st orders of diffraction of the grating) is controlled very simply and precisely by shifting the position of the grating in its plane. We generate high harmonic orders from the two bright lobes and record the beating between the two emissions for each harmonic order up to the 53rd harmonic order.

We present characterizations of the attosecond pulse train produced in the high harmonic generation (HHG) from SF6 molecules irradiated by a strong pulsed laser field at 800 nm. At harmonic order 17, we observe a minimum in the amplitude of the emitted spectrum and a corresponding distortion in the phase. Our experimental results are compared to two models: a multicenter interference model focused on the effect of the structure of the SF6 molecule in HHG and a model focused on the interferences between multiple ionization channels in HHG. We find that the experimental results agree very well with the multiple ionization channels model, illustrating that HHG in molecules can be very complex and that it provides insights of the intramolecular electron dynamics during the interaction process.