Overview of progress in construction and testing of the laser systems of ELI-Beamlines, accomplished since 2015, is presented. Good progress has been achieved in construction of all four lasers based largely on the technology of diode-pumped solid state lasers (DPSSL). The first part of the L1 laser, designed to provide 200 mJ <15 fs pulses at 1 kHz repetition rate, is up and running. The L2 is a development line employing a 10 J / 10 Hz cryogenic gas-cooled pump laser which has recently been equipped with an advanced cryogenic engine. Operation of the L3-HAPLS system, using a gas-cooled DPSSL pump laser and a Ti:sapphire broadband amplifier, was recently demonstrated at 16 J / 28 fs, at 3.33 Hz rep rate. Finally, the 5 Hz OPCPA front end of the L4 kJ laser is up running and amplification in the Nd:glass large-aperture power amplifiers was demonstrated.
Large laser systems that deliver optical pulses with peak powers exceeding one Petawatt (PW) have been constructed at dozens of research facilities worldwide and have fostered research in High-Energy-Density (HED) Science, High-Field and nonlinear physics . Furthermore, the high intensities exceeding 10<sup>18</sup>W/cm<sup>2</sup> allow for efficiently driving secondary sources that inherit some of the properties of the laser pulse, e.g. pulse duration, spatial and/or divergence characteristics. In the intervening decades since that first PW laser, single-shot proof-of-principle experiments have been successful in demonstrating new high-intensity laser-matter interactions and subsequent secondary particle and photon sources. These secondary sources include generation and acceleration of charged-particle (electron, proton, ion) and neutron beams, and x-ray and gamma-ray sources, generation of radioisotopes for positron emission tomography (PET), targeted cancer therapy, medical imaging, and the transmutation of radioactive waste [2, 3]. Each of these promising applications requires lasers with peak power of hundreds of terawatt (TW) to petawatt (PW) and with average power of tens to hundreds of kW to achieve the required secondary source flux.
Overview of the laser systems being built for ELI-Beamlines is presented. The facility will make available high-brightness multi-TW ultrashort laser pulses at kHz repetition rate, PW 10 Hz repetition rate pulses, and kilojoule nanosecond pulses for generation of 10 PW peak power. The lasers will extensively employ the emerging technology of diode-pumped solid-state lasers (DPSSL) to pump OPCPA and Ti:sapphire broadband amplifiers. These systems will provide the user community with cutting-edge laser resources for programmatic research in generation and applications of high-intensity X-ray sources, in particle acceleration, and in dense-plasma and high-field physics.
The ELI Beamlines facility will house repetition rate high-power lasers with pulse durations down to 15 fs and over petawatt peak powers. Our research group participates in the construction of a cryogenically cooled Yb:YAG multi-slab amplifier; part of the L2 beamline. The system shall provide square, super-Gaussian beam with nearly 2 ns pulses with rectangular temporal profile and energy of up to 10 J at 10 Hz. The laser will provide pump beams for broadband OPCPA stages. The diagnostic system of the pump laser is critical for the correct performance analysis, stabilization feedback and mostly for the machine interlock system as damages of the expensive optical components can develop very fast with the 10 Hz repetition rate. The diagnostic system provides key laser parameters and characteristics in temporal, spectral and spatial domain. The paper describes testing of the setup for measurements of the final 10 J output. Its design is based on a combination of optical wedges and diffractive sampler to facilitate multiple diagnostics on a relatively small footprint. The laser diagnostics package covers measurements in spatial domain such as near-field, far-field, or wavefront analysis, further optical spectrum, pulse energy and temporal shape. In order to detect possible damage dark-field analysis was implemented as well. The final setup was modeled in optical design software (Radiant Zemax) to understand its behavior and later tested together with real-time LabVIEW code developed by our group as being part of the machine interlock system. The first results of the tests as well as detailed description of the diagnostics package design are presented.
We present an overview of the projected and/or implemented laser systems for ELI-Beamlines. The ELI-Beamlines
facility will be a high-energy, high repetition-rate laser pillar of the ELI (Extreme Light Infrastructure) project. The
facility will make available high-brightness multi-TW ultrashort laser pulses at kHz repetition rate, PW 10 Hz repetition
rate laser pulses, and kilojoule nanosecond laser pulses that will be used for generation of 10 PW, and potentially higher,
peak power. These systems will allow meeting user requirements for cutting-edge laser resources for programmatic
research in generation and applications of high-intensity X-ray sources, in electron and proton/ion acceleration, and in
dense plasma and high-field frontier physics.