Large-aperture pulse compression grating (PCG) is a critical component in generating an ultra-high-intensity, ultra-short-pulse laser, however, the size of PCG manufactured by transmission holographic exposure is limited to large-scale high-quality materials. The reflective method is a potential way for solving the size limitation, but there is still no successful precedent due to the lack of scientific specifications and advanced processing technology of exposure mirrors. In this paper, an analytical model is developed to clarify the specifications of mirrors and advanced processing technology is adopted to control the spatial frequency errors. Hereafter, we have successfully fabricated a multilayer dielectric (MLD) grating of 200 mm × 150 mm by using off-axis reflective exposure system with Φ300 mm. This demonstration proves that PCGs can be manufactured by using reflection holographic exposure method and shows the potential for manufacturing of meters-level gratings used in 100 Pettwatt class high-power laser.

Gérard Mourou received his PhD from Pierre and Marie Curie University in 1973. He and his student Donna Strickland co-invented chirped pulse amplification (CPA) technology and shared the 2018 Nobel Prize in Physics. This technology made it possible to apply ultrafast lasers to many new areas such as eye surgery, precision manufacturing, particle physics and nuclear fusion. Gérard Mourou is the founding Director of the Center for Ultrafast Optical Science (CUOS) at the University of Michigan and the initiator of the Extreme Light Infrastructure (ELI) in Europe.

Vladimir Tikhonchuk, Professor Emeritus at Centre Lasers Intenses et Applications, University of Bordeaux, France, and senior researcher at the Extreme Light Infrastructure ERIC, ELI-Beamlines Facility, Czech Republic. His research is in the domain of high energy density physics and nonlinear optics, including inertial confinement fusion, dynamic processes in laboratory astrophysics, laser-plasma interactions, excitation of parametric instabilities, generation of magnetic and electric fields, acceleration of charged particles, and energy transport.

The recent achievement of fusion ignition with laser-driven technologies at the National Ignition Facility sets a historic milestone in fusion energy research. This paves the way to the use of laser inertial fusion as a viable approach for energy production. Europe has a unique opportunity to empower research in this field. We propose establishing a European program on Inertial Fusion Energy with the mission to demonstrate laser-driven ignition in the direct drive scheme and to develop pathway technologies for the commercial fusion reactor. The roadmap is based on: i) the physics of laser plasma interaction, ii) high energy high repetition rate laser technology, iii) reactor technology and materials and iv) education and training. A collaboration with universities, research centers, industry and private sector is expected. Along with the high level socio-economic impact, this project stimulates a broad range of high profile industrial developments in laser, plasma and radiation technologies.

A fully automatic fail-safe beam shaping system based on a liquid crystal on silicon spatial light modulator has been implemented in the high-energy kilowatt-average-power nanosecond laser system Bivoj. The shaping system corrects for gain non-uniformity and wavefront aberrations of the front-end of the system. The beam intensity profile and the wavefront at the output of the front-end were successfully improved by shaping. The beam homogeneity defined by beam quality parameters was improved 2-3 times. The RMS value of the wavefront was improved more than 10 times. Consequently, the shaped beam from the second pre-amplifier led to improvement of the beam profile at the output of the first main cryo-amplifier. The shaping system is also capable of creating non-ordinary beam shapes, imprinting cross references into the beam or masking certain part of the beam.

The production of broadband, terawatt terahertz (THz) pulses has been demonstrated by irradiating relativistic lasers on solid targets. However, the generation of extremely powerful, narrow-band, and frequency-tunable THz pulses remains a challenge. Here, we present a novel approach for such THz pulses, in which a plasma wiggler is elaborated by a table-top laser and a near-critical density plasma. In such a wiggler, the laser-accelerated electrons emit THz radiations with a period closely related to the plasma thickness. Theoretical model and numerical simulations predict a THz pulse with a laser-THz energy conversion over 2.0%, an ultra-strong field exceeding 80 GV/m, a divergence angle approximately 20◦, and a center-frequency tunable from 4.4 to 1.5 THz, can be generated from a laser of 430 mJ. Furthermore, we demonstrate that this method can work across a wide range of laser and plasma parameters, offering potential for future applications with extremely powerful THz pulse.

With the increasing power of fiber lasers, single chirped and titled fiber Bragg gratings (CTFBGs) cannot completely mitigate continuously enhanced system-excited stimulated Raman scattering (SRS). Although improving the loss rate of a single CTFBG or cascading multiple CTFBGs can provide better suppression of the stronger SRS, excessive insertion loss may cause significant attenuation of the output power. Confronting the challenge, we firstly present an SRS mitigation method based on dual-structured fiber grating in this paper. The dual-structure fiber grating comprises a CTFBG and a fiber Bragg grating (FBG) structure, which were designed and fabricated on a passive 25/400 double-clad fiber. To evaluate the performance of the grating, a 3 kW fiber MOPA laser is established. The experimental results demonstrate that the SRS mitigation rate of the grating is greater than 30 dB (99.9%), whereas the insertion loss is only approximately 3%, thus allowing for minimal deterioration of the output power.

Multilayer dielectric gratings (MLDGs) are crucial for pulse compression in picosecond-petawatt laser systems. Bulged nodular defects, embedded in coating stacks during multilayer deposition, influence the lithographic process and performance of the final MLDG products. In this study, the integration of nanosecond laser conditioning (NLC) into different manufacturing stages of MLDG was proposed for the first time: on multilayer dielectric films (MLDFs) and final grating products to improve laser-induced damage performance. The results suggest that the remaining nodular ejection pits introduced by the two protocols exhibit a high nanosecond-laser damage resistance, which remains stable when the irradiated laser fluence is more than twice the nanosecond-laser-induced damage threshold (nanosecond-LIDT) of the unconditioned MLDGs. Furthermore, the picosecond-LIDT of the nodular ejection pit conditioned on the MLDFs was ~40 % higher than that of the nodular defects, and the loss of the grating structure surrounding the nodular defects was avoided.

Diode-pumped rare gas lasers are potential candidates for high-energy and high-beam quality laser systems. Currently, most investigations are focused on metastable Ar lasers. The Kr system has the unique advantages of higher quantum efficiency and lower discharge requirements for comparison. In this paper, a diode-pumped metastable Kr laser was demonstrated for the first time. Using a repetitively pulsed discharge at a Kr/He pressure up to ~1500 torr, the metastable Kr atoms of >1013 cm-3 were generated. Under diode pumping, the laser realized a dual-wavelength output with an average output power of ~100 mW and an optical conversion efficiency of ~10% with respect to the absorbed pump power. A Kinetics study involving population distribution and evolution was conducted to analyze the laser performance.

In this work, we experimentally investigate the dependence of the stimulated Raman scattering (SRS) effect on the seed’ s linewidth of high-power nanosecond superfluorescent fiber source (ns-SFS). The results reveal that the SRS in ns-SFS amplifier is significantly influenced by the full width at half maximum (FWHM) of the ns-SFS seed, and there is an optimal FWHM linewidth of 2 nm to achieve the lowest SRS in our case. The first-order SRS power ratio increases rapidly when the seed’ s linewidth deviates from the optimal FWHM linewidth. By power-scaling ns-SFS seed with optimal FWHM linewidth, a narrowband all-fiberized ns-SFS amplifier is achieved with a maximum average power of 602 W, pulse energy of 24.1 mJ, and corresponding peak power of 422.5 kW. This is the highest average power and pulse energy for all-fiberized ns-SFS amplifiers to the best of our knowledge.