We measured the groove pattern of the diffraction gratings with an aperture of 690 x 420 mm by three different interferometers at two wavelengths with spatial resolution 0.3 mm. The measured 2D power spectrum density of both the groove pattern and the substrate surface profile were power dependent with exponents 3.5 and 2.5 in the wavevector range from 0.003 to 1 mm(-1) . To improve pulse contrast, it is necessary to improve substrate polishing, and to increase focal intensity, it is necessary to improve the quality of the optics used to record the gratings or (preferably) to polish the grating substrates, striving for an optimal surface that compensates for the imperfection of the groove pattern rather than a perfectly flat one. Using the measured groove pattern we numerically studied focal intensity reduction versus a beam aperture for the different compressor designs.

Manufacturing imperfections in large-aperture holographic gratings critically limit multi-petawatt Chirped Pulse Amplification systems. This study investigates their impact on wavefront quality using Zemax ray-tracing simulations based on real interferometric measurements. The results confirm that distortions are cumulative, with imperfections in the second and third gratings primarily driving beam degradation. Significantly, we demonstrate that rotating these critical gratings by 180° alters the residual wavefront structure. The study concludes that optimizing grating orientation, combined with adaptive optics, is an effective strategy to mitigate aberrations and restore peak intensity, offering vital guidelines for next-generation high-field laser facilities.

Non-equidistant and non-parallel grooves of a diffraction grating distort the diffracted wavefront. For a fixed wavelength, a grating with an arbitrary groove pattern is equivalent to a grating with perfect grooves having an effective surface profile different from the geometric one. It is shown that the previously proposed method for measuring non-equidistance can be used for simultaneous measurement of non-parallelism, and the measurement error is determined without any a priori information and fitting parameters. The demonstrated error (RMS) for the diffraction gratings with an aperture of 320 x 230 mm manufactured by us was 2 nm for the effective profile, 4 10-7for non-equidistance, and 4.5 10-7 for the groove inclination angle when measuring with a spatial resolution of 0.27 mm. Rms of the wavefront distortions of the beam reflected from these gratings was 10 +/- 2 nm. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Magnetic nanoparticles, consisting of a metallic iron core with a shell of gold and iron oxides, were synthesized by ultra-high vacuum surface nucleation on a water-soluble NaCl substrate followed by oxidation in water. Using the methods of electron microscopy, electron diffraction, photoelectron spectroscopy and calculation of the specific density of iron in the oxidized shell, the oxides gamma-Fe2O3, Fe3O4 and oxyhydroxide alpha-FeO(OH) were discovered. A non-uniform distribution of the Fe3+/Fe2+ ion ratio over the particle depth and a predominance of alpha-FeO(OH) in the contrast shell of nanoparticles, directly observed in transmission electron microscopy, were discovered. Comparison of the magnetic properties of partially gold-coated particles with similar Fe particles without gold showed a larger residual volume of unoxidized metal core with partial gold coating. This points to the anisotropy of the surface chemical properties associated with the Janus-like structure. For the first time, the magnetodynamic properties of partially gold-coated Fe nanoparticles were assessed by ellipsometric measurements of the surface of a colloidal solution in a gradient magnetic field.

Femtosecond pulse shaping is a variety of experimental methods for manipulating temporal profile of ultrashort laser pulses. One of common tools for pulse shaping is acousto-optic programmable Bragg gratings. We describe the Dispersive Fourier Synthesis algorithm for generating arbitrary transmission functions of acousto-optic programmable dispersive filters and delay lines used therein. The algorithm performs computation of radio-frequency waveforms providing arbitrary complex-valued transmission functions for the said devices. An open-source MATLAB script was developed based on this algorithm taking into account the ease of use of a commercial radio-frequency driver. The experiments include full validation of the algorithm: calibration of frequency-to-wavelength mapping, determination of optimal driving power, and closed-loop femtosecond pulse compression in the front-end of the PEARL (PEtawatt pARametric Laser) facility.

A proof-of-principle experiment of highly efficient (38%) second harmonic generation was implemented at a ∼1T W/c m 2 intensity of a 45 fs pulse in a composite nonlinear sample-a 1 mm KDP crystal glued onto a 1 mm fused silica substrate. The attenuated replica of the second harmonic pulse (455 nm) was compressed down to 28.6 fs by means of dispersive mirrors, with a significant reduction in both the wings and the far temporal contrast. The peak power of the second harmonic was ∼74% of the power of the fundamental harmonic, which ensured a three-fold increase in the focal intensity.

The PEARL laser -plasma complex is set up on the basis of a petawatt laser and allows a wide range of experiments in laser -plasma interactions, including particle acceleration, X-ray generation, and research in the area of high energy density physics. Constant work to improve the system makes it possible not only to systematically expand experimental capabilities but also to develop new technologies for megascience class facilities. The paper outlines possible experimental scenarios for using the laser and provides a description of experiments already carried out with the laser in a broad range of areas.

We performed an experiment on the acceleration of electrons in the laser peeler regime during the interaction of a focused subpetawatt laser pulses with solid-state targets. Electrons with energies up to 70 MeV were produced, and their directional pattern was determined. The use of serrated targets led to an increase in the maximum energies and the number of accelerated electrons. A numerical study conducted using particle-in-cell simulation showed good agreement with the experimental results.

Fluence fluctuations on the fourth compressor grating limit the energy, power, and, ultimately, the focal intensity of ultra-high-power femtosecond lasers. Significant smoothing of output fluence fluctuations in various asymmetric compressors was demonstrated experimentally. The compressor symmetry was broken as a result of different angles of incidence of the beam on the first and third gratings in the horizontal plane, in the vertical plane, and in both planes simultaneously. Two-dimensional spatial spectra of the fluctuation suppression ratio were measured and proved to be in good agreement with the theory presented earlier. Specifically, if the angle of incidence on the third grating in the vertical plane is only 1 deg, the fluctuations with a scale of 2.5 mm or less are suppressed by two orders training, and similar technologies, are reserved.

Analytical expressions for the spatial spectrum of fluence fluctuations of a laser pulse propagating in a medium with Kerr nonlinearity have been obtained. It is shown that inhomogeneities with a spatial scale much larger than the critical scale of self-focusing grow insignificantly even at large values of the B-integral. Experiments using BK7 glass and a KDP crystal as a nonlinear medium confirm the obtained theoretical results. This may be interesting for pulse post-compression, frequency doubling, and other experiments using transmission optical elements in ultra-high intensity lasers.

A new front-end laser system with optical synchronization of chirped femtosecond and pump pulses for the petawatt laser complex PEtawatt pARametric Laser (PEARL) has been developed. The new front-end system provides a broader femtosecond pulse spectrum, temporal shaping of the pump pulse, and a significant increase in the stability of the parametric amplification stages of the PEARL.

Dynamics of optical discharge glow in a subsonic argon flow is determined in experiments using a continuously pumped, Q -switched repetitively pulsed CO 2 (CPQS) laser. The features of the laser plasma glow are revealed for the first time: a two-lobe structure at an early stage of the discharge process and a subsequent appearance of an extended glow region in the laser beam in front of the plasma. Compared with the results of calculating the space–time scales of laser plasma at the initial stage of the process, the experimental data indicate an uncharacteristic sequence of plasma propagation regimes—from a light-supported detonation wave to a fast ionization wave.

It was shown experimentally that for a 65-fs 17-J pulse, the effect of filamentation instability, also known as small-scale self-focusing, is much weaker than that predicted by stationary and nonstationary theoretical models for high B-integral values. Although this discrepancy has been left unexplained at the moment, in practice no signs of filamentation may allow a breakthrough in nonlinear pulse post-compression at high laser energy.

PEARL laser facility was the first PW-class laser based on OPCPA, in which a peak power of 0.56 PW was achieved back in 2007 [1]. Since then, this facility has been actively used for studies in the field of laser physics and laser-matter interaction. Now, this facility is under upgrade. The Compression after Compressor Approach (CafCA) for additional nonlinear pulse compression [2], installation of a deformable mirror for a focal spot improvement [3] and pump laser optimization were implemented on PEARL facility. The main drawback of the PEARL laser setup is the instability of the electrical synchronization between the fs signal and pump pulses. But, both laser-matter interaction and implementation of CafCA and deformable mirror requires improving of pulse-to-pulse stability of PEARL laser.

The eXawatt Center for Extreme Light Studies project aimed to create a large scientific infrastructure based on lasers with giant peak power. The project relies on the significant progress achieved in the last decade. The planned infrastructure will incorporate a unique light source with a pulse power of 600 PW using optical parametric chirped pulse amplification in large-aperture KD2PO4, deuterated potassium dihydrogen phosphate crystals. The interaction of such laser radiation with matter represents a completely new fundamental physics. The direct study of the space-time structure of vacuums and other unknown phenomena at the frontier of high-energy physics and the physics of superstrong fields will be challenged. Expected applications will include the development of compact particle accelerators, the generation of ultrashort pulses of hard X-ray and gamma radiation for material science enabling one to probe material samples with unprecedented spatial and temporal resolution, the development of new radiation and particle sources, etc. The paper is translation from Russian [Kvantovaya Elektronika 53, 95 (2023)].

We present the first experimental results obtained with a setup created on the basis of the PEARL laser facility for studying the processes of generating terahertz radiation from laser wake fields which are formed during the propagation of a high-power femtosecond laser pulse in a rarefied plasma. In particular, the occurrence of terahertz generation in the case where the laser–plasma interaction region is located between a pair of dielectric prisms of total internal reflection is demonstrated. The dependence of the terahertz radiation energy on the energy of a femtosecond laser pulse and on the plasma density is studied.

The use of the post-compression technique ensures gain in laser pulse peak power but at the same time degrades beam focusability due to the nonlinear wavefront distortions caused by a spatially nonuniform beam profile. In this paper a substantial focusability improvement of a post-compressed laser pulse by means of adaptive optics was demonstrated experimentally. The Strehl ratio increase from 0.16 to 0.43 was measured. Simulations showed that the peak intensity in this case reaches 0.52 of the theoretical limit.

The 18J, 60fs laser pulse was compressed to 10fs after passing through KDP crystal and reflecting from chirping mirrors. The experiments were performed at В-integral up to 19 without visible damages of the optical elements.

Mn5Ge3 epitaxial thin films previously grown mainly on Ge substrate have been synthesized on Si(111) using the co-deposition of Mn and Ge at a temperature of 390 °C. RMS roughness decreases by almost a factor of two in the transition from a completely polycrystalline to a highly ordered growth mode. This mode has been stabilized by changing the ratio of the Mn and Ge evaporation rate from the stoichiometric in the buffer layer. Highly ordered Mn5Ge3 film has two azimuthal crystallite orientations, namely Mn5Ge3 (001) [1-10] and Mn5Ge3 (001) [010] matching Si(111)[-110]. Lattice parameters derived a (7.112(1) Å) and c (5.027(1) Å) are close to the bulk values. Considering all structural data, we proposed a double buffer layer model suggesting that all layers have identical crystal structure with P6₃/mcm symmetry similar to Mn5Ge3, but orientation and level of Si concentration are different, which eliminates 8% lattice mismatch between Si and Mn5Ge3 film. Mn5Ge3 film on Si(111) demonstrates no difference in magnetic properties compared to other reported films. TC is about 300 K, which implies no significant excess of Mn or Si doping. It means that the buffer layer not only serves as a platform for the growth of the relaxed Mn5Ge3 film, but is also a good diffusion barrier.

The output pulse of the PEARL was compressed to 10 fs by reflecting from chirped mirrors after propagation through Kerr nonlinear medium. The power was more than 1.5 PW. It is the shortest pulse for all petawatt lasers.