Joule class lasers at 100Hz with ultra-short pulse involve a lot of challenges to manage thermal issues in the amplifiers as well as in the compressors. Recent results achieved in this direction are presented.

Particle flux is not enough for societal applications when using TW/PW class lasers to generate high energy electron. To overcome this, we have developed a 100 Hz Joule class TiSa laser and report initial results.

Modern laser plasma accelerators require combination of high peak power and high average power from the laser. Ti:Sa CPA remaining the best technology for such purpose a high average power Ti:Sa amplifier has been developed

We report a full experimental comparison study on the injection of a Ti:Sa multi-TW amplifier chain with a standard 15 fs Ti:Sa oscillator and a 35 fs frequency doubled fiber oscillator. The study highlights that the Ti:Sa oscillator with high performances in term of pulse duration and spectral width can be replaced by the frequency doubled fiber oscillator to seed Ti:Sa amplifier chains without almost any compromise on the output pulse duration and the picosecond contrast. Finally, we demonstrate for the first time of our knowledge a 30 TW and 33 fs Ti:Sa amplifier injected by a fiber oscillator.

We report a full experimental comparison study on the injection of a Ti:Sa multi-terawatt amplifier chain with a standard 15 fs Ti:Sa oscillator and 35 fs frequency-doubled fiber oscillator. The study highlights that the Ti:Sa oscillator, with high performance in terms of pulse duration and spectral width, can be replaced by the frequency-doubled fiber oscillator to seed Ti:Sa amplifier chains almost without any compromise on the output pulse duration and picosecond contrast. Finally, we demonstrate for the first time to our knowledge a 30 TW and 33 fs Ti:Sa amplifier injected by a fiber oscillator.

The demonstration of the first 10 PW pulses during March 2019 the High Power Laser System at ELI-NP together with extensive tests, provides now the possibility to evaluate the ultrahigh irradiance in reach.

We report the generation of unprecedented 10 PetaWatt laser pulses obtained from each of the two beamlines of the High Power Laser System (HPLS) of ELI-NP (Extreme Light Infrastructure – Nuclear Physics) research infrastructure. The laser system is a hybrid system made of a double CPA based on amplification within Titanium Sapphire crystals combined with an OPCPA with a parametric amplification stage boosting the energy to 10 mJ at the entrance of the second CPA. A XPW filter is also inserted between the two CPA and in combination with the OPCPA improves the temporal contrast of the pulses by typically 7 orders of magnitude. The spectral effects occurring during amplification such as gain narrowing and wavelength shifting are compensated through the use of spectral filters. Final amplification stages are involving large aperture Ti:Sapphire crystals (up to 200 mm) which are pumped by high energy frequencydoubled Nd:Glass lasers delivering each 100 J of green light. Laser beams have been amplified respectively up to 332 J and to 342 J of pulse energy at 1 shot per minute without any occurrence of ASE and transverse lasing thanks to index matching fluid surrounding the crystal over is entire length and pump deposition management over the time before each beam pass within the Ti:Sapphire crystal. We have demonstrated full aperture compression by metric gratings of these amplified pulses down to 22.6 fs and therefore made the full demonstration for the first time ever of 10 PW capability from a laser system.

We report on a two-arm hybrid high-power laser system (HPLS) able to deliver 2 × 10 PW femtosecond pulses, developed at the Bucharest-Magurele Extreme Light Infrastructure Nuclear Physics (ELI-NP) Facility. A hybrid front-end (FE) based on a Ti:sapphire chirped pulse amplifier and a picosecond optical parametric chirped pulse amplifier based on beta barium borate (BBO) crystals, with a cross-polarized wave (XPW) filter in between, has been developed. It delivers 10 mJ laser pulses, at 10 Hz repetition rate, with more than 70 nm spectral bandwidth and high-intensity contrast, in the range of 1013:1. The high-energy Ti:sapphire amplifier stages of both arms were seeded from this common FE. The final high-energy amplifier, equipped with a 200 mm diameter Ti:sapphire crystal, has been pumped by six 100 J nanosecond frequency doubled Nd:glass lasers, at 1 pulse/min repetition rate. More than 300 J output pulse energy has been obtained by pumping with only 80% of the whole 600 J available pump energy. The compressor has a transmission efficiency of 74% and an output pulse duration of 22.7 fs was measured, thus demonstrating that the dual-arm HPLS has the capacity to generate 10 PW peak power femtosecond pulses. The reported results represent the cornerstone of the ELI-NP 2 × 10 PW femtosecond laser facility, devoted to fundamental and applied nuclear physics research.

Applications using multi-PW lasers necessitate high temporal pulse quality with a tremendous contrast ratio (CR). The first crucial prerequisite to achieve multi-PW peak power is the generation of ultrashort pulses with good spectral phase quality. Second, to avoid any deleterious pre-ionization effect on targets, nanosecond contrast better than 1012 is also targeted. In the framework of the Apollon 10 PW French laser program, we present a high-contrast 10 fs front-end design study to inject highly energetic Ti:sapphire PW lasers. The CR has been measured and analyzed in different time ranges highlighting the different major contributions for each scale.

A laser system made of two beams of 10 PW each has been designed and is currently built for ELI-NP research infrastructure. Design is presented as well as preliminary results up to the 1PW level amplifier.

We present a high-contrast 10-fs Front-End for Ti:sapphire PW-lasers within the Apollon-10PW project. This injector uses OPCPA pumped at 100Hz by Yb-based CPA chain. Combination of OPCPA and XPW permits a >1012 contrast ratio.

The objective of the Apollon project is the generation of 10 PW peak power pulses of 15 fs at 1 shot/minute. In this paper the Apollon facility design, the technological challenges and the current progress of the project will be presented.

We present the research advances on the development of 50-200 mJ energy range diode-pumped Yb:CaF 2 -based multipass amplifiers operating at relatively high repetition rates. These laser amplifiers are based on diverse innovative geometries. All these innovations aim to design compact, stable, and reliable amplifiers adapted to our application that consists in pumping ultrashort-pulse optical parametric chirped pulse amplifier systems in the frame of the Apollon 10-PW laser project. The targeted repetition rate is in the range of 20-100 Hz with energies of few tens of mJ for the first stages up to 1 J for the final stage. An analysis of the specificities of Yb:CaF 2 is done to explain the different options, we chose to fulfil these specifications. The critical points and limitations of the multipass Yb:CaF 2 -based amplifiers are subsequently discussed. To overcome the encountered problems, different issues are investigated such as crystal optimisation, laser head geometry, thermo-optical dynamics, or coherent combining techniques. Experimental results for different multipass configurations are demonstrated and discussed.

A hybrid Ti:Sa CPA/BBO OPCPA system with a XPW filter inbetween the two has been developed to produce a broadband high contrast seeder of 10 mJ for the two 10 PetaWatt beamlines of ELI NP infrastructure.

The dynamic thermal issues of the Yb:CaF\(_{2}\) crystals within a multi-tens-mJ-energy multipass amplifier operating in the 20–100 Hz repetition rate range and pumped in quasi-cw regime have been studied at different timescales. Thermal response times of the system have been precisely investigated and analyzed, for the first time to our best knowledge in such amplifiers. This study includes a dual timescale analysis: in the long-time-scale (second) with direct thermography mapping and in the millisecond range with thermal lensing in a pump-probe configuration. Very atypical positive lens behavior with fluorites will also be presented and discussed. This complete analysis is used to demonstrate the capability of \(\hbox {Yb:CaF}_{2}\) multipass amplifier systems for operating the amplifier at 20 Hz with 57 mJ and 100 Hz with 32-mJ stable regime. Indeed, high repetition rate multipass amplifier has been realized for the first time with \(\hbox {Yb:CaF}_{2}\) and for this energy. The results have been analyzed precisely to take into account the thermal issues and excellent beam quality, with a \(M^2\) of 1.1. The pointing stability of 20 μrad has been measured documenting the reliability of the high repetition rate mJ amplifier.

The Apollon-10P is a laser infrastructure aiming to realize experiments at 10 PW peak power. It will be used to drive ultra-intense and ultra-short sources of particles (electrons, protons...), and for the generation of coherent and high energetic X rays. This laser facility is a multi beam line composed of one main laser expected to deliver on target 10 PW pulses at 1 shot per minute repetition rate (150 J in 15 fs at 800 nm), a 1 PW beam line, a probe with 10 TW and an uncompressed beam with an energy up to 250 J.

A compact and robust, dual-crystal cross polarized wave generation setup combined with a hollow waveguide filter is implemented to deliver few-cycle, high-contrast laser pulses sourced from a commercial multipass Ti:Sa amplifier. The initial 25-fs pulses with a temporal contrast of 10(8) are shortened to 10 fs with an improved contrast of at least 10(10). The single nonlinear stage for spectral broadening and contrast enhancement of a commercial amplifier serves as an ideal injector for petawatt-class laser systems. (C) 2013 Optical Society of America

We present the development of the front-end of the Apollon 10PW laser. It is based on broadband OPCPA stages pumped by high energy diode pumped Yb based amplifiers to produce up to 30 mJ, 10-fs pulses at 20-100 Hz to seed Ti:Sapphire amplifiers.

We are presenting a 57 mJ multipass amplifier based on Yb:CaF2 operating at 20 Hz. Special attention has been given to the thermal measurement and management in order to push it to the 100 Hz regime.