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High-energy hybrid femtosecond laser system demonstrating 2 × 10 PW capability

The pursue for high peak power is driven by the uncharted territory of knowledge that this may unlock, from basic science to applied one. The optical path towards these phenomenal powers may be one of the natural ones when we observe the critical role that the light is playing in the universe.

In the past several years, there has been significant progress in developing femtosecond high-power laser systems by using Chirp Pulse Amplification (CPA) technique, proposed by the Nobel Laureates, Donna Strickland and Gerard Mourou in 1985. The combination of laser media having broad emission spectral bandwidth and the use of Optical Parametric Chirp Pulse Amplification (OPCPA) in nonlinear crystals with large parametric gain bandwidth, as proposed by A. Dubietis et al. in 1992, made possible the demonstration of several Petawatt (PW) class femtosecond laser systems. They can be found in the C. N. Danson et al. review of the filed, published in 2019 in High Power Laser Science and Engineering (Colin N. Danson, et al. Petawatt and exawatt class lasers worldwide[J]. High Power Laser Science and Engineering, 2019, 7(3): 03000e54).

Recently, Dr. Ioan Dancus et al 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 facility. The related research results are published in High Power Laser Science and Engineering, Vol. 8, Issue 4 (François Lureau, Guillaume Matras, Olivier Chalus, et al. High-energy hybrid femtosecond laser system demonstrating 2 × 10 PW capability[J]. High Power Laser Science and Engineering, 2020, 8(4): 04000e43).

The initial stage of this laser system is a hybrid Front-End (FE) based on Ti:sapphire CPA and picosecond OPCPA based on Beta Barium Borate (BBO) crystals, with a crossed polarized wave filter (XPW) in between. The FE delivers 10 mJ laser pulses, at 10 Hz repetition rate, with more than 70 nm spectral bandwidth and full width half maximum 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/minute repetition rate. The measured 327 J chirped pulse energy at the output of the final amplifier. Corroborated with the 74.2% transmission efficiency of the 10 PW temporal compressor and the 22.7 fs pulse duration, measured at attenuated pulse energy, demonstrate that the high energy femtosecond laser system has the capacity to deliver 10 PW laser pulses.

The system was designed starting from the requirements of a user facility, and the redundant FE and the additional available pumping energy are providing the required margins for a high beam availability for the users. In addition, the spatial wavefront and spectral phase control by using the deformable mirrors and Dazzler provide tools for ensuring flexibility in the achievement of the user required beam parameters in the focal region.

The reported repetition rate, pointing and energy stability demonstrates the reliability of the laser system. The repetition rate of one shot per minute is the highest reported for a 10 PW laser system, to the researchers' knowledge.

In the latest time, the 10 PW Laser Beam Transport System (LBTS) was tested, and a full power 10 PW endurance test of the entire system was performed. During this test, the researchers assessed a complete set of parameters like the wavefront and the near field irradiance profile. This test results will be the subject of a follow-up paper that will concentrate on the parameters of the beam delivered for the users.

The high-energy hybrid femtosecond laser system developed at the Bucharest-Magurele Extreme Light Infrastructure – Nuclear Physics facility

Focusing and high peak irradiance assessment will be done in the near future. Based on the seeding of the two high energy amplification arms from a common Front-End, future experiments of 2 × 10 PW femtosecond laser pulses synchronization are expected.

The reported results represent a milestone in the implementation of a fully functional 2 × 10 PW femtosecond laser driven nuclear physics facility at the Bucharest-Magurele Extreme Light Infrastructure – Nuclear Physics. The core mission of this ultra-intense laser facility is to use extreme fields and pressure generated with high power femtosecond laser pulses for fundamental and applied nuclear physics research as described by S. Gales et al. in Reports on Progress in Physics 81, 094301 (2018) and K.A. Tanaka et al. in Matter and Radiation at Extremes 5, 024402 (2020).

Extreme Light Infrastructure Nuclear Physics (ELI-NP) Phase II, is a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund and the Competitiveness Operational Programme (1/07.07.2016, COP, ID 1334).

Researchers gratefully acknowledge the contribution of the entire Thales and ELI-NP teams and collaborators.