27 W 2.1 µm OPCPA system for coherent soft X-ray generation operating at 10 kHz

© 2020 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved.We developed a high power optical parametric chirped-pulse amplification (OPCPA) system at 2.1 µm harnessing a 500 W Yb:YAG thin disk laser as the only pump and signal generation source. The OPCPA system operates at 10 kHz with a single pulse energy of up to 2.7 mJ and pulse duration of 30 fs. The maximum average output power of 27 W sets a new record for an OPCPA system in the 2 µm wavelength region. The soft X-ray continuum generated through high harmonic generation with this driver laser can extend to around 0.55 keV, thus covering the entire water window (284 eV - 543 eV). With a repetition rate still enabling pump-probe experiments on solid samples, the system can be used for many applications.EC/H2020/654148/EU/The Integrated Initiative of European Laser Research Infrastructures/LASERLAB-EUROP

Prospects of target nanostructuring for laser proton acceleration

In laser-based proton acceleration, nanostructured targets hold the promise to allow for significantly boosted proton energies due to strong increase of laser absorption. We used laser-induced periodic surface structures generated in-situ as a very fast and economic way to produce nanostructured targets capable of high-repetition rate applications. Both in experiment and theory, we investigate the impact of nanostructuring on the proton spectrum for different laser-plasma conditions. Our experimental data show that the nanostructures lead to a significant enhancement of absorption over the entire range of laser plasma conditions investigated. At conditions that do not allow for efficient laser absorption by plane targets, i.e. too steep plasma gradients, nanostructuring is found to significantly enhance the proton cutoff energy and conversion efficiency. In contrast, if the plasma gradient is optimized for laser absorption of the plane target, the nanostructure-induced absorption increase is not reflected in higher cutoff energies. Both, simulation and experiment point towards the energy transfer from the laser to the hot electrons as bottleneck

27 W 2.1 µm OPCPA system for coherent soft X-ray generation operating at 10 kHz

We developed a high power optical parametric chirped-pulse amplification (OPCPA) system at 2.1 µm harnessing a 500 W Yb:YAG thin disk laser as the only pump and signal generation source. The OPCPA system operates at 10 kHz with a single pulse energy of up to 2.7 mJ and pulse duration of 30 fs. The maximum average output power of 27 W sets a new record for an OPCPA system in the 2 µm wavelength region. The soft X-ray continuum generated through high harmonic generation with this driver laser can extend to around 0.55 keV, thus covering the entire water window (284 eV - 543 eV). With a repetition rate still enabling pump-probe experiments on solid samples, the system can be used for many applications. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

High peak and average power Ti:sapphire thin disk amplifier with extraction during pumping

The combination of the extraction during pumping (EDP) amplification scheme and the thin disk (TD) technology has been successfully applied to the Ti:sapphire (Ti:sa) laser medium for the first time, to the best of our knowledge. In a proof-of-principle experiment, we demonstrate high energy broadband amplification in a room temperature water cooled EDP-TD head of stretched femtosecond pulses at a 10 Hz repetition rate, instead of performing a cryogenically cooled traditional multi-pass scheme. Hence, the EDP-TD combination can overcome the limits associated with thermal effects and transverse amplified spontaneous emission, enabling Ti:sa laser systems to have a petawatt peak and hundreds of watts of average power. (C) 2016 Optical Society of Americ

Modeling of electron dynamics in laser-irradiated solids: progress achieved through a continuum approach and future prospects

International audienceA continuum model based on a drift-diffusion approach is applied to describe the dynamics of electronic excitation, heating and charge-carrier transport in metals and dielectrics under near-infrared femtosecond laser irradiation. The dependence of laser-induced charging of the targets on laser fluence and pulse duration is investigated. Various aspects concerning the mechanism of Coulomb Explosion (CE) are discussed. The CE threshold as a function of pulse duration is evaluated numerically for dielectric materials (sapphire and ULE glass). A special attention is paid to studies of interconnection between the electron emission yield and surface charging dynamics. It has been found that in dielectrics the photoemission yield saturates with increasing laser fluence as a result of self-regulation of the free-electron population. By contrast in metals, due to effective supply of electrons to the charging zone on the target surface, electron emission becomes unwarrantably high for short laser pulses and high fluences. However, photo- and thermionic emissions can be suppressed by the generated electric field whose amplitude is a function of pulse duration and laser fluence. The question on self-consistency of electron emission and surface charging is analyzed with outlining further studies