LiGaS2 crystals are prospective media for optical parametric oscillators. In such systems efficiency and maximum power output are often limited by the laser-induced damage threshold (LIDT) of nonlinear crystals. In addition, most nonlinear crystals have a high refractive index and consequently large Fresnel losses, thus encouraging the use of antireflection coatings. However, antireflection coatings are known to compromise the LIDT. This work presents results of the LIDT testing of LiGaS2 nonlinear crystals in untreated, antireflection-coated and antireflection-microstructured variations. The tests were performed using a one-on-one method with pulsed lasers operating at 1.57, 2.09 and 2.5 μm wavelengths with pulse durations of 9, 149 and 12 ns, respectively. The paper covers damage site feature investigation and LIDT comparison of antireflection coating and antireflection microstructures. The key finding of the work is that antireflection microstructures can provide an increase in transmittance for both the pump and the signal, while maintaining a high LIDT.

We demonstrate the effective compensation of carrier envelope phase (CEP) slip in a high-power femtosecond laser using a machine-learning (ML)-based control scheme. The compensation is achieved through fine dispersion tuning guided by a recurrent neural network (RNN) that predicts the temporal evolution of CEP slip, combined with a reinforcement-learning (RL) scheme that determines the optimal corrective actions. With this RNN+RL framework, the integrated CEP noise is reduced by more than a factor of two compared with a conventional proportional–integral–derivative controller. The proposed ML-based control methodology provides a versatile tool for stabilizing and optimizing various parameters in high-power laser systems.

Deep learning (DL) has been applied to phase control in coherent beam combining (CBC) recently. However, existing DL-based approaches for filled-aperture CBC essentially convert the phase-locking path into tiled-aperture schemes. Consequently, common-path phase locking in DL-based filled-aperture CBC remains unrealized. Common-path refers to a phase-locking scheme in which the phase information is extracted from the combined beam after the same combining system. In this paper, a common-path phase-locking method is proposed. By exploiting the intrinsic nonuniformity, each laser source is effectively labeled, enabling a mapping between the combined speckle and the multi-source phase. A neural network is employed to reconstruct the phase. Simulations with 25-channel CBC demonstrate a phase-locking accuracy of up to λ/39. Notably, it remains effective under dynamic phase disturbances. Our work presents a common-path phase-locking approach based on a neural network for filled-aperture CBC, which can offer a new solution for the field.

A spatiotemporal optical vortex (STOV) with transverse orbital angular momentum can induce some novel properties in high-energy-density physics. However, the current STOV pulse energy is limited to the mJ level, which greatly hinders the development of the research field of relativistic laser–matter interaction. Combined with the large-scale grating pair in high-peak-power laser facilities, a method for generating STOVs with ultra-high intensity of up to 1021 W/cm2 is proposed. The numerical simulation proves that a wave packet with 60 fs duration and 83 J energy can be generated in the far-field, maintaining an integral spatiotemporal vortex construction. Simultaneously, STOVs with 1.1 mJ single-pulse energy were obtained in a proof-of-principle experiment, and characterized by a home-made measuring device.

Surface defects on fused silica optics significantly limit their laser-induced damage resistance under ultraviolet pulsed laser irradiation, yet quantitative correlations between defect parameters and damage thresholds remain scarce. This study is the first to perform multimodal detection and correlation analysis of laser-induced damage initiated at real defects on fused silica. Scratches were characterized by scattered light intensity, width and fluorescence intensity, and correlated with the damage-onset fluence (DOF). Results show trailing indent scratches (1.9–8.8 μm wide) have DOFs of 1.27–13.2 J/cm2, while plastic continuous scratches (0.4–5.8 μm wide) exhibit higher DOFs of 12.3– 22.0 J/cm2. Fluorescence intensity strongly negatively correlates with DOF (p < 0.001), as do scratch width and fluorescence intensity at α = 0.01 (p < 0.01). These findings establish scratch width and fluorescence intensity as quantitative damage precursors, advancing surface quality assessment for high-energy laser optics.

We present an experimental study on electron and X-ray generation from the interaction of a hundreds of TW femtosecond laser with microchannels. Leveraging the guiding effect of the channel structure on both the laser and electrons, a well-collimated electron beam is achieved, with a beam charge of 1.5 nC (>10 MeV), a slope temperature of 9.1 MeV and a nearly constant divergence angle (~14°) over a broad energy range (10–50 MeV). Meanwhile, we demonstrate a ring-shaped X-ray source generated through bremsstrahlung radiation mechanism from electrons collision with channel walls, exhibiting a characteristic energy of 90 keV and emittance of 0.8 mm mrad. Three-dimensional simulations elucidate the underlying acceleration dynamics. It is found that elongated channels facilitate the formation of well-collimated electron beams. These results establish the foundation for applications of channel guided electrons and secondary radiation sources and represent a key step toward the controlled manipulation of particle sources in laser-driven plasmas.

A high-power, efficient pulsed amplifier based on a laser diode end-pumped ytterbium-doped yttrium aluminum garnet (Yb:YAG) rod was demonstrated. The crystal’s reabsorption was effectively minimized by optimizing the amplifier’s parameters through numerical simulations, leading to a power extraction efficiency of up to 56%. A compensation method was applied to correct the beam distortion caused by thermally induced birefringence in the Yb:YAG rod. Furthermore, a remarkably low depolarization rate of 2.2% was achieved, along with an average power output of 483 W. The beam quality factor (M2) of the amplified signal was improved to below 1.3, following compensation of the thermally induced spherical aberration using a phase plate. To the best of our knowledge, this achievement represents the highest average power and efficiency for fundamental mode operation in an Yb:YAG rod amplifier at room temperature.

The traditional design of laser drivers for inertial confinement fusion (ICF) is highly dependent on coherent laser light fields, which have significant advantages in achieving harmonic conversion and enhancing amplification efficiency. However, they also bring the core challenge of achieving uniform irradiation. This paper investigates the dynamic evolution process of uniform irradiation of multi-mode spatiotemporal light fields and analyzes the influence mechanism of spatiotemporal coherence on irradiation uniformity with different integration times. By balancing the relationship between the spatiotemporal coherence of the light field and uniform irradiation, we explore a possible scheme to alleviate the beam smoothing problem while satisfying the basic requirements of laser amplification and high-efficiency harmonic conversion. Based on this scheme, the overall architecture of the ICF laser driver is constructed.

We report on the development of a carrier-envelope phase (CEP)-stable 1030 nm fiber-based laser system producing 6.2 fs pulses achieved via the multi-pass cell (MPC) post-compression technique with 402 W average power at 100 kHz repetition rate. This system employs an upgraded three-stage MPC compression scheme exhibiting excellent beam quality properties for this intensity region. Active stabilization locks the CEP noise below 430 mrad root mean square. This work represents the first demonstration of a coherently combined fiber laser system simultaneously achieving such exceptional average power, CEP stability and sub-two-cycle pulse durations. Similar to all other light sources of the Extreme Light Infrastructure Attosecond Light Pulse Source, this newly developed system is accessible to the international research community in peer-reviewed open user calls of the Extreme Light Infrastructure European Research Infrastructure Consortium.

In this work, an innovative scheme is proposed that exploits the response of magnetized plasmas to realize a refractive index exceeding unity for right circularly polarized waves. Using two- and three-dimensional particle-in-cell simulations with the OSIRIS 4.0 framework, it is shown that a shaped magnetized plasma lens (MPL) can act as a glass/solid-state-based convex lens, enhancing laser intensity via transverse focusing. Moreover, by integrating three key ingredients, a tailored plasma lens geometry, a spatially structured strong magnetic field and a suitably chirped laser pulse, simultaneous focusing and compression of the pulse has been achieved. The simulations reveal up to a 100-fold increase in laser intensity, enabled by the combined action of the MPL and the chirped pulse profile. With recent advances in high-field magnet technology, shaped plasma targets and controlled chirped laser systems, this approach offers a promising pathway toward experimentally reaching extreme intensities.

Multi-plane light conversion (MPLC) is a versatile technique that enables arbitrary manipulation of optical fields, and is numerically investigated as a novel avenue for coherent beam combining (CBC) applications. The optical parameters have been investigated to guide the MPLC design, indicating that the number of phase planes and plane spacing serve as pivotal factors. The channel scalability is simulated, revealing that the plane spacing should be increased in a larger array to maintain high performance under a few-plane limit. CBC of up to 1027 lasers has been numerically demonstrated with near-diffraction-limited beam quality (M2 of 1.16 and combining efficiency close to 100%) with only seven phase plates. Beam steering is investigated, revealing that steering capability is related to both the number of multiplexed modes in MPLC and their mode fidelities, and the main-lobe power ratio of 87.1% at one divergence angle is achieved in a 10-mode MPLC with five phase plates.

We present a high-brightness, nanosecond pulsed blue laser source at 476.8 nm through efficient quadruple-harmonic generation from a thulium-doped yttrium lithium fluoride (Tm:YLF) master oscillator power amplifier operating at 1.9 μm. The fundamental-frequency stage produces 42 mJ pulses at 1907.3 nm with a narrow linewidth of 0.19 nm at 1 kHz. Through cascade second-harmonic generation using low-walk-off lithium triborate crystals, we achieve 10.52 mJ blue laser pulses with 16.1 ns duration, corresponding to a peak power of 0.65 MW and exhibiting excellent energy stability of 0.47%. The system maintains exceptional beam quality (M2x = 1.46, M2y = 1.27) at maximum output power, attributed to the negative thermal-optical properties of the Tm:YLF crystal, end-pumped amplification architecture and optimized nonlinear conversion. This work demonstrates a compact and efficient route to high-brightness (~2.49 GW·cm–2·sr–1) pulsed blue laser emission, which is particularly suitable for advanced marine scientific applications including underwater LiDAR and communication systems.

To mitigate inhomogeneous thermal and stress effects caused by multi-pulse accumulation in laser–material interactions, we propose an all-optical strategy to generate a structured beam, termed a ‘drill-like laser’, featuring a petal-shaped intensity profile with stochastic rotation by shot-to-shot control. The strategy involves generating collinear signal and idler pulses carrying conjugated orbital angular momenta via optical parametric amplification (OPA). The pulses then interfere with each other to form a beam with petal-shaped intensity structure, whose orientation is governed by their carrier-envelope phase (CEP) difference. The strategy is further implemented with a dual-stage OPA system pumped by an 800-Hz–30-fs–800-nm femtosecond laser, where the CEP difference is directly controlled by the pump CEP. Experimentally, a drill-like laser at 1.6 μm is demonstrated with stochastic shot-to-shot intensity rotation, resulting from the shot-to-shot random fluctuation of the pump CEPs, which has been validated using dual-line pump–probe detection via sum-frequency generation. Crucially, since the interference arises from two beams with free-space eigenmodes, rather than angular-dispersion-based spatiotemporal coupling, the drill-like laser maintains high propagation stability and is scalable in power by conventional laser amplification, holding great potential for applications in precision laser processing and other high-field scenarios.

Spectral broadening via phase modulation is widely employed in high-power laser systems to suppress transverse-stimulated Brillouin scattering and improve beam uniformity. However, nonuniform spectral transmittance and group velocity dispersion can induce frequency modulation-to-amplitude modulation (FM-to-AM), threatening the safety of large-aperture optics. Current monitoring techniques rely on high-speed oscilloscopes and wavelength conversion, thereby increasing the cost and complexity. This study presents a real-time FM-to-AM detection method based on a dual-comparator delay-unlocked detection architecture. The system employs a high-speed photodetector, low-noise amplifier, envelope detection and delay-unlocked dual comparator. The module reliably measures modulation depths from 1.27% to 19.15% for pulses with a rise time of less than 60 ps and a modulation frequency of 20 GHz. This compact, low-cost and modular design enables robust FM-to-AM monitoring without high-speed oscilloscopes, facilitating real-time feedback and enhancing operational stability in large-scale laser drivers, while offering scalability for multi-channel deployment in future inertial confinement fusion facilities.

Laser-driven plasma wakefield acceleration (LWFA) offers exceptionally high acceleration gradients and can produce high-brightness electron beams. However, the laser-to-electron energy conversion efficiency typically remains limited to a few percent. Theoretically, the self-mode transition from LWFA to beam-driven plasma wakefield acceleration (PWFA) provides a pathway for fully utilizing the laser energy. Here, we demonstrate the single-stage LPWFA (hybrid LWFA–PWFA) scheme, validated through comparative experiments using a 300 TW tightly focused laser interacting with sub-critical density nitrogen gas targets. The experiments produce an electron beam with charge of approximately 31 nC above 6 MeV and approximately 116 nC above 2 MeV. The laser-to-electron energy conversion efficiency is approximately 6.1% (>6 MeV) and 16.4% (>2 MeV), respectively. Particle-in-cell simulations confirm that the single-stage LPWFA mechanism depletes the laser energy and enables continual electron injection. This high-charge, multi-MeV electron beam has great value in the generation of high-brightness $\unicode{x3b3}$-rays and high-flux neutron sources.

A setup based on magnetic levitation technologies was created to demonstrate credible solutions in the area of cryogenic fuel target (CFT) noncontact transport and their repeatable injection. A necessary element is a levitating CFT carrier made from Type-II, high-temperature superconductors (HTSCs). This paper discusses four principal categories: (1) a tandem HTSC–carrier configuration; (2) a linear permanent magnet guideway to maintain a friction-free acceleration of the HTSC–carrier; (3) a spring mechanism for driving the HTSC–carrier; (4) an optical tracking system to control the HTSC–carrier and injected targets motion. In demo experiments (T = 80 K), a magnetic track oriented S-N-S (size 360 mm × 24 mm × 5 mm) had a large cross-sectional gradient ΔВ = 0.33 T at the edges of the track forming the so-called ‘magnetic wall’ to provide a lateral stability of the HTSC–carrier trajectory. Acceleration and braking of the HTSC–carrier containing two surrogate targets was recorded, followed by targets injection with a rate of 10–25 Hz.

We report a high-power, high-repetition-rate, Yb-doped fiber femtosecond master-oscillator power-amplifier (MOPA) system. Based on an all-fiber-based chirped pulse amplification configuration comprising a Yb fiber mode-locked seed source, a five-stage repetition-rate multiplier, three Yb-doped fiber amplifiers and a pulse compressor, the MOPA system yielded 1.06 kW of femtosecond pulsed output at 1040 nm with a pulse duration of 356 fs at a repetition rate of 1.83 GHz. Furthermore, a modified seed source incorporating spectral reshaping and additional pulse stretching enabled an improved compressed pulse shape with significantly reduced sidelobes, leading to a shorter pulse duration of 275 fs at the maximum output power. The prospects for a further increase in power and energy via this approach are considered.

Cylindrical vector (CV) $\gamma$ rays can introduce spatially structured polarization as a new degree of freedom for fundamental research and practical applications. However, their generation and control remain largely unexplored. Here, we put forward a novel method to generate CV $\gamma$ rays with tunable hybrid polarization via a rotating electron beam interacting with a solid foil. In this process, the beam generates a coherent transition radiation field and subsequently emits $\gamma$ rays through nonlinear Compton scattering. By manipulating the initial azimuthal momentum of the beam, the polarization angle of $\gamma$ rays relative to the transverse momentum can be controlled, yielding tunable hybrid CV polarization states. Three-dimensional spin-resolved particle-in-cell simulations demonstrate continuous tuning of the polarization angle across $\left(-90{}^{\circ},\ 90{}^{\circ}\right)$ with a high polarization degree exceeding 60%. Our work contributes to the development of structured $\gamma$ rays, potentially opening up new avenues in high-energy physics, nuclear science and laboratory astrophysics.

We propose a method for the cut-off of stimulated rotational Raman scattering (SRRS) in high-power lasers after long-distance propagation via a transmission volume Bragg grating (VBG). The VBG with both spectral and angular selectivity was designed, and its application as a near-field spatial filter for SRRS cut-off was analyzed. The results show that the spectral selectivity of the VBG enables effective separation of pump light and Stokes light in the near-field, and also improves the beam quality by filtering out high-frequency components of the pump light. This method can provide a novel and effective approach for suppressing nonlinear effects and controlling the beam quality of high-power lasers.

Polarized particle sources have a plethora of applications, ranging from deep-inelastic scattering to nuclear fusion. One crucial challenge in laser–plasma interaction is maintaining the initial polarization of the target. Here, we propose the acceleration of spin-polarized helium-3 from near-critical density targets using high-intensity Laguerre–Gaussian laser pulses. Three-dimensional particle-in-cell simulations show that magnetic vortex acceleration with these modes yields high polarization at the $90\%$ level, while also providing low-divergence beams.