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

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

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

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

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

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