17 research outputs found
Spatio-temporal characterisation of a 100 kHz 24 W sub-3-cycle NOPCPA laser system
In recent years, OPCPA and NOPCPA laser systems have shown the potential to supersede Ti:sapphire plus post-compression based laser systems to drive next generation attosecond light sources via direct amplification of few-cycle pulses to high pulse energies at high repetition rates. In this paper, we present a sub 3-cycle, 100 kHz, 24 W NOPA laser system and characterise its spatio-temporal properties using the SEA-F-SPIDER technique. Our results underline the importance of spatio-temporal diagnostics for these emerging laser systems
Towards High-Energy Few-Cycle Optical Vortices with Minimized Topological Charge Dispersion
A simple approach to generate high-energy few-cycle optical vortices with
minimized topological charge dispersion is introduced. By means of numerical
simulations it is shown that, by leveraging the intrinsic properties of optical
parametric chirped pulse amplification (OPCPA), clean transfer of topological
charge from a high energy narrowband pump pulse to a broadband idler is
feasible under certain particular conditions, enabling the generation of
high-energy few-cycle vortex pulses with extremely low topological charge
dispersion
Numerical study of spatiotemporal distortions in noncollinear optical parametric chirped-pulse amplifiers
During amplification in a noncollinear optical parametric amplifier the spatial and temporal coordinates of the amplified field are inherently coupled. These couplings or distortions can limit the peak intensity, among other things. In this work, a numerical study of the spatiotemporal distortions in BBO-based noncollinear optical parametric chirped-pulse amplifiers (NOPCPAs) is presented for a wide range of parameters and for different amplification conditions. It is shown that for Gaussian pump beams, gain saturation introduces strong distortions and high conversion efficiency always comes at the price of strong spatiotemporal couplings which drastically reduce the peak intensity even when pulse fronts of the pump and the signal are matched. However, high conversion efficiencies with minimum spatiotemporal distortions can still be achieved with flat-top pump beam profiles
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Spatio-temporal characterisation of a 100 kHz 24 W sub-3-cycle NOPCPA laser system
In recent years, OPCPA and NOPCPA laser systems have shown the potential to supersede Ti:sapphire plus post-compression based laser systems to drive next generation attosecond light sources via direct amplification of few-cycle pulses to high pulse energies at high repetition rates. In this paper, we present a sub 3-cycle, 100 kHz, 24 W NOPA laser system and characterise its spatio-temporal properties using the SEA-F-SPIDER technique. Our results underline the importance of spatio-temporal diagnostics for these emerging laser systems
Retrieval of attosecond pulse ensembles from streaking experiments using mixed state time-domain ptychography
The electric field of attosecond laser pulses can be retrieved from laser-dressed photoionisation measurements, where electron wavepackets that result from single-photon ionisation by the attosecond pulse in the presence of a dressing field are produced. In case of fluctuating dressing laser and/or attosecond pulses, e.g. due to pulse-to-pulse fluctuations of the carrier envelope phase of the infrared laser pulse, commonly applied retrieval algorithms result in the erroneous extraction of the pulse fields. We present a mixed state time-domain ptychography algorithm for the retrieval of pulse ensembles from attosecond streaking experiments
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Strong field ionization of small hydrocarbon chains with full 3D momentum analysis
Strong field ionization of small hydrocarbon chains is studied in a kinematic complete experiment using a reaction microscope. By coincidence detection of ions and electrons different ionization continua populated during the ionization process are identified. In addition, photoelectron momentum distributions from laser-aligned molecules allow to characterize the electron wavepackets emerging from different Dyson orbitals
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Retrieval of attosecond pulse ensembles from streaking experiments using mixed state time-domain ptychography
The electric field of attosecond laser pulses can be retrieved from laser-dressed photoionisation measurements, where electron wavepackets that result from single-photon ionisation by the attosecond pulse in the presence of a dressing field are produced. In case of fluctuating dressing laser and/or attosecond pulses, e.g. due to pulse-to-pulse fluctuations of the carrier envelope phase of the infrared laser pulse, commonly applied retrieval algorithms result in the erroneous extraction of the pulse fields. We present a mixed state time-domain ptychography algorithm for the retrieval of pulse ensembles from attosecond streaking experiments. © 2020 The Author(s). Published by IOP Publishing Ltd
Photoelectron imaging of XUV photoionization of CO2 by 13-40 eV synchrotron radiation
Valence band photoionization of CO2 has been studied by photoelectron
spectroscopy using a velocity map imaging spectrometer and synchrotron
radiation. The measured data allow retrieving electronic and vibrational
branching ratios, vibrationally resolved asymmetry parameters, and the total
electron yield which includes multiple strong resonances. Additionally, the
spectrum of low kinetic energy electrons has been studied in the resonant
region, and the evolution with photon energy of one of the forbidden
transitions present in the slow photoelectrons spectrum has been carefully
analyzed, indicating that in the presence of auto-ionizing resonances the
vibrational populations of the ion are significantly redistributed
Generation and characterisation of few-pulse attosecond pulse trains at 100 kHz repetition rate
The development of attosecond pump–probe experiments at high repetition rate requires the development of novel attosecond sources maintaining a sufficient number of photons per pulse. We use 7 fs, 800 nm pulses from a non-collinear optical parametric chirped pulse amplification laser system to generate few-pulse attosecond pulse trains (APTs) with a flux of >106 photons per shot in the extreme ultraviolet at a repetition rate of 100 kHz. The pulse trains have been fully characterised by recording frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG-CRAB) traces with a velocity map imaging spectrometer. For the pulse retrieval from the FROG-CRAB trace a new ensemble retrieval algorithm has been employed that enables the reconstruction of the shape of the APTs in the presence of carrier envelope phase fluctuations of the few-cycle laser system