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.

Transverse mode instability (TMI) is a primary limitation for power scaling in high-brightness fiber lasers. This paper reports observation of the TMI effect in the process of supercontinuum generation, and demonstrates a 993 W linearly polarized supercontinuum ranging from 800 to 2000 nm through an amplifier-based structure. To mitigate TMI, three strategies are implemented: repetition rate doubling to reduce peak power and mitigate the thermal loading; reducing the bending radius of the gain fiber to suppress higher-order modes; optimizing the polarization extinction ratio of the pre-amplifier. TMI-induced beam quality degradation and power-scaling limitation resemble those of conventional fiber lasers. In particular, burr-like spectral fluctuations in supercontinuum sources are observed upon the onset of TMI. This work deepens the understanding of TMI mechanisms in broadband laser systems and offers critical guidance for power scaling of high-power supercontinuum sources.

High-energy vortex beams with transverse orbital angular momentum (TOAM) have significant applications in many fields. However, generating such beams with well-defined spatiotemporal (ST) field structures at energies beyond extreme ultraviolet is still a major challenge. Here, we demonstrate the generation of coherent X-ray spatiotemporal optical vortices (STOVs) with definitive mode-resolved, ST field-level structures through nonlinear Thomson scattering of a near-infrared STOV laser pulse by a relativistic electron beam in a nanometer-scale thickness. Our far-field time-domain radiation simulations confirm that the generated X-ray harmonics are STOV pulses with well-defined STOV structures, where the vortex charge scales linearly with the harmonic order, in accordance with TOAM conservation. The emission is highly collimated within approximately 4 mrad. The formation of coherent STOV structures requires tight temporal synchronization, spatial confinement and phase matching of the radiation fields from individual electrons in the electron beam. Excessive laser beam sizes induce spectral broadening and phase mismatches, which degrade coherence and suppress the emergence of well-defined STOV harmonics. This study presents a new approach for generating highly collimated X-ray STOVs, with potential applications in nuclear physics, ultrafast dynamics and structured light–matter interactions at the nanoscale.

We present a novel, compact resonator design for large-mode thin-disk lasers, producing 300 W average output power at a 1-kHz repetition rate within a cavity length of less than 5 m. High beam quality with M2x = 1.06 and M2y = 1.15 is achieved by breaking conventional mode-matching ratios and fully exploiting the disk’s soft-aperture effect. In this work, an ytterbium-doped yttrium aluminum garnet thin-disk resonator is shown to produce fundamental transverse mode lasing with a mode size approaching or surpassing the pump spot dimension. Theoretical analysis demonstrates that the proposed cavity configuration enables a thin-disk regenerative amplifier to deliver pulse energy exceeding 200 mJ at 1 kHz repetition rate with excellent beam quality.

An exawatt-class peak-power laser architecture, based on a single, large-aperture Nd:mixed-glass amplifier combined with a technique called chirped pulse juxtaposed with beam amplification (CPJBA) is proposed to significantly extend laser capabilities beyond the present 10 PW state-of-the-art for ultra-high-intensity lasers. CPJBA utilizes a space–time coupled chirped-beam pulse to enhance the temporal compression of a fixed-aperture grating pair in a novel six-grating compressor arrangement. With this, an appropriately structured, 20-ns stretched pulse can be compressed to a transform limit of 100 fs using a maximum grating aperture of 2 m. This enables the extraction of 25 kJ of energy from a single, large-aperture Nd:glass beamline while staying below the B-integral threshold. This paper presents the numerical modeling of the various novel sub-systems required for this exawatt-class laser architecture. In particular, the unique spatial and temporal pulse distortions present during amplification using CPJBA, and the strategies used to mitigate them, are discussed.

In 2019 we published the extensive review paper ‘Petawatt and exawatt class lasers worldwide’ in High Power Laser Science and Engineering. We are delighted that the review has achieved over 1000 citations on Google Scholar and over 750 on Web of Science. We take this opportunity to reflect on the current state of the field.

Power scaling of neodymium (Nd)-doped single-frequency fiber lasers (SFFLs) operating at approximately 900 nm has been fundamentally constrained by dominant emission of approximately 1060 nm, with previous demonstrations limited to below 3 W. Here, we demonstrate a 910 nm single-mode Nd-doped SFFL system that achieves a record output power of over 30 W employing homemade Nd-doped silica fiber (NDF), while preserving exceptional 49 dB suppression of competing emission of approximately 1060 nm. The laser system originates from a distributed Bragg reflector single-frequency (SF) oscillator with 11 mW output power, which is subsequently amplified to 31.1 W through three polarization-maintaining (PM) amplification stages utilizing PM 10/125 μm NDF. To the best of our knowledge, this represents the highest power achieved for Nd-doped SFFLs in this spectral region. The output exhibits excellent beam quality (Mx2 = 1.03, My2 = 1.05) and narrow linewidth (10.2 kHz). These results validate that the homemade PM 10/125 μm NDF can be employed in intermediate and main amplifiers in all-fiber SF master oscillator power amplifier systems at approximately 900 nm.

At the low-coherence Kunwu laser facility with a 0.6% bandwidth, we experimentally studied the laser absorption efficiency of laser–target coupling at intensities of (3–5) × 1014 W cm–2. To characterize side scattering across a wide angular range, we developed a novel radiochromic film-based diagnostic system, which enables continuous spatial mapping over approximately π steradians for the first time. The results indicate a substantial reduction in total loss rate (by more than three times) when compared to a monochromatic laser. We focused on analyzing the influence of laser bandwidth on stimulated Brillouin scattering and stimulated Raman scattering (SRS). Notably, we found that the broadband laser enhances SRS at high intensities, which is contrary to the results obtained at low intensities. These results highlight the role of bandwidth as a quantitative control parameter for improving laser–plasma coupling, which is of particular significance for advancing direct-drive inertial confinement fusion.

This study reports a new optically addressed spatial light modulator (OASLM) structure based on bilateral-sapphire substrates with an air gap that exhibits high-average-power laser resistance. The resistance of traditional OASLMs to high-average-power laser irradiation is primarily affected by the high absorption of the transparent conductive film and low thermal conductivity of the substrate. Thermodynamic simulations indicated that the thermal conductivity of a sapphire substrate was significantly higher than that of K9 glass. Using sapphire as the substrate significantly reduced the temperature increase of indium tin oxide. An OASLM based on this structure, without any auxiliary cooling measures, exhibited a higher high-average-power laser resistance (170 W/cm2) than that of a K9 glass OASLM (9 W/cm2).

Ultrafast vortex beams are essential in many scientific and industrial fields owing to their unique spatial and temporal characteristics. We demonstrate a passively mode-locked ytterbium-doped yttrium aluminum garnet (Yb:YAG) thin-disk oscillator that directly generates high-power femtosecond vortex beams with excellent beam quality. Using Kerr-lens mode-locking assisted by a semiconductor saturable absorber mirror, we achieve 594 fs Laguerre–Gaussian vortex pulses with 50 W average power at a 68.5 MHz repetition rate, representing the highest power reported for a femtosecond vortex oscillator. By replacing the planar output coupler with a coated axicon, we further realize stable mode-locking and efficient generation of first-order Bessel vortex beams. This compact and integrated design eliminates external mode converters, enabling robust generation of high-power ultrafast structured light. The demonstrated source provides a promising platform for precision material processing, strong-field vortex dynamics and quantum optical studies.

We have investigated the equation of state (EoS) of hexagonal boron nitride (h-BN) under extreme conditions using the Prague Asterix Laser System facility. The experiment employed a 438 nm wavelength laser pulse with a pulse duration of approximately 350 ps delivering up to 200 J of energy. A phase plate ensured a uniform flat-top intensity profile with a diameter of approximately 400 μm. Shock wave velocities were simultaneously determined in BN and in a reference material from time- and space-resolved self-emission measurements using a streaked optical pyrometer. The EoS of BN was determined by comparing its response to that of the reference material. We achieved high compression of BN (up to 9 Mbar). By expanding the experimental dataset on the EoS of h-BN, this study contributes to a more comprehensive understanding of behavior of this material under extreme conditions, supporting advancements in fusion energy research, high-energy-density physics and possibly next-generation inertial confinement fusion target designs.

Nd,Y:CaF2 (NYCF) crystals are exceptional gain materials for high-power laser drivers; however, laser-induced damage remains a substantial challenge that restricts their broader application. In this study, by establishing an in situ testing system for photothermal weak absorption and the laser-induced damage threshold (LIDT), the relationship between the photothermal weak absorption characteristics of NYCF and its LIDTs was analyzed. A fully connected neural network was employed to facilitate deep learning of these relationships, thereby enabling non-destructive evaluation of NYCF via photothermal weak absorption. Moreover, this study examined both the effect of spot size during testing and the influence of crystal orientation on the evaluation outcomes. The underlying mechanisms were further elucidated by investigating NYCF’s thermal mechanical properties and damage characteristics. This work not only offers a rapid, non-destructive method for evaluating the laser damage resistance of NYCF using artificial intelligence but also enhances the understanding of its damage mechanisms.

We propose a new compressor geometry – a full-aperture two-grating slanted-groove compressor (F2SC), consisting of two parallel Littrow-mounted gratings with slanted grooves. The angle of the slanting is chosen so as to ensure decoupling of the input and output beams. The gratings and the beam on the first grating have the same size. Optimal parameters of this and other previously proposed compressor geometries are found analytically, considering restrictions not only on the grating length but also on its height. It is shown that, similar to a full-aperture two-grating Treacy compressor (F2TC), the F2SC provides maximum power and focal intensity. The advantages of these geometries are the absence of hot spots on the second (last) grating due to beam smoothing. Power above 160 PW and focal intensity up to 5.5 × 1024 W/cm2 at the F/2 parabola seem quite achievable with the grating sizes of 150 cm × 122 cm for the F2SC and 162 cm × 108 cm for the F2TC. Another advantage of the F2SC is the potential possibility of using multilayer dielectric gratings.

With the advancement of high-intensity laser (HIL) technology, laser-induced plasma can produce short-lived nuclear isomers, which hold significant research value in fields such as nuclear-excitation mechanisms, nuclear clocks and radioactive medicine. However, due to intense electromagnetic pulses (EMPs) and X-rays, the detection of the short-lived isomers is still challenging today. To address this, an optical-fiber-coupled scintillator detection method is proposed in this study. The method can overcome the dilemma that traditional real-time detection methods face when struggling with the complex electromagnetic and radiation environment generated by HIL experiments, enabling real-time detection of characteristic signals on the nanosecond time scale during experiments. Employing a PW-level femtosecond laser-pumping ${}^{83}$Kr to the $7/2+$ metastable state, which has a half-life of 156.94 ns, the de-excitation gamma-rays were detected successfully by the proposed detection system for the first time. This method addresses critical challenges in EMP-dominated HIL environments, enables investigations of ultra-fast nuclear processes and further advances experiments related to high-repetition-rate intense lasers.

We report here the characteristics of a high-power continuous-wave mid-infrared (mid-IR) fiber light source based on nested anti-resonant hollow-core fiber (AR-HCF) filled with HBr gas. A homemade hundred-watt-level 2 μm narrow-linewidth fiber laser is constructed as the pump source. The pump source is forward injected into the AR-HCF through a single-pass configuration. A maximum output power of 10.4 W at 4.16 μm with excellent beam quality (M2) of approximately 1.05 is achieved in a 4.8 m long AR-HCF at gas pressure of 9.9 mbar, with a slope efficiency of 20% relative to the absorbed pump power. The mid-IR light source maintains good stability during long-term operation. To the best of our knowledge, this is the highest output power for silica-based fiber light sources beyond 4 μm. This work demonstrates the significant capability of power scaling in a gas-filled AR-HCF mid-IR light source.

Precise control of the polarization of X-ray lasers is crucial in broad applications such as ultrafast-physics experiments and material characterization. Existing X-ray polarization converters, however, are mainly suited for low-power conditions and usually suffer from either large size or low conversion efficiency. Here we propose a compact and efficient scheme for polarization conversion of high-power, high-intensity femtosecond X-ray lasers, based on linear total internal reflection at the interface of the vacuum and solid-density plasma plate. Particle-in-cell simulations show that although the reflectivity is affected by the density oscillations of the surface plasma waves that are inevitably excited, the single-pass reflectivity can still exceed 95% and approach 100% for a broad range of laser parameters. Beyond its high conversion efficiency and damage resistance, this method offers dynamic tunability and enables ultrafast polarization switching (sub-ps), positioning it as a compact and innovative solution for polarization control in high-power X-ray laser systems.

In this work, we experimentally demonstrate a high-power supercontinuum (SC) that covers from visible to mid-infrared (MIR) in a GeO2-core fiber (GCF) bundle via incoherent beam combination. In the experiment, the SC generation in a single GCF was initially explored, and an SC spanning from visible to MIR regions was obtained, with average power of less than 10 W. To increase the output power, we fabricated a 3×1 high-power GCF-based tapered fiber bundle, incoherently combining three channels of the previously mentioned replicas. This yielded a broadband SC spectrum with a maximum average power of 23.1 W and a spectral bandwidth covering 0.73–3.1 μm. The obtained spectrum power fluctuation was measured over 1 hour, showing a root mean square value of 0.7%. To the best of our knowledge, this represents the highest power SC from visible to MIR regions obtained in GCFs pumped by 1.55 μm high-power pulses.

Optical parametric chirped-pulse amplification (OPCPA) is a promising approach for generating intense vortex pulses over a broad spectrum. However, its intrinsic parametric superfluorescence (PSF) noise significantly degrades the spatial and temporal contrast of the amplified vortex pulses. Here, we investigate the PSF evolution dynamics during OPCPA of ultrafast vortex pulses and propose three effective strategies to suppress PSF. Our findings indicate that strong vortex seeding can effectively suppress PSF overlapping spatially and temporally with the vortex, but it fails to suppress PSF near the vortex singularity. After focusing, the PSF near the singularity tends to spread into a larger spot than the vortex, allowing for its removal through a far-field spatial aperture. Alternatively, employing a vortex pump can completely prevent such PSF. These research results offer valuable insights for the development of high-contrast vortex OPCPA systems.

The properties of warm dense matter are crucial for understanding the physics underlying star formation, stellar evolution and inertial confinement fusion (ICF). We present soft X-ray measurements of a well-isolated warm dense plasma system produced by the collision of high-speed plasma jets in ICF-related experiments with double-cone targets. The colliding plasma was found to exhibit a structure consisting of a hotter inner core and a colder outer shell. The core region emits continuum Planckian radiation with an effective temperature of $45.53\pm 0.44\;\mathrm{eV}$. The outer shell, which has electron density of around ${10}^{23}\;{\mathrm{cm}}^{\hbox{--} 3}$ and temperature of $34.26\pm 2.12\;\mathrm{eV}$, introduces absorption lines of carbon ions superposed on the continuum spectra. Two-dimensional radiation hydrodynamic simulations and synthetic X-ray spectral images reveal the detailed physical processes determined with the experimental measurements.