Continuous-wave diamond Raman lasers (DRLs) operated at high pump power commonly suffer from power roll-off and output instability, even when high-thermal-conductivity gain media are employed. These degradations originate from thermally induced cavity-mode mismatch and cavity-length drift, which limit further power scaling. In this work, we establish a thermo–optical chain-linked model that quantitatively describes the coupled evolution of thermal deposition, equivalent thermal lensing, intracavity-mode matching and output power in high-power DRLs, providing a direct physical link between pump power and cavity-length compensation. Based on this model, a peak–valley co-location criterion is proposed to determine the optimal cavity-length compensation point. Both theoretical and experimental results show that the output power exhibits a single-peak dependence on cavity-length offset, while the power stability follows a U-shaped distribution, and their extrema coincide at an optimal compensation value ΔL*. By operating at ΔL*, the maximum Stokes output power increases from 27 to 32 W, and the root mean square power fluctuation decreases from 4.8% to 3.2%. These results demonstrate that thermal-lens-induced performance degradation can be effectively mitigated by cavity-length compensation using a single control parameter, providing a practical design rule for simultaneous enhancement of output power and stability in high-power Raman laser systems.

Laser-driven sources are quickly becoming an important instrument in several areas of research. Recent developments of high-repetition-rate lasers (multi-TW at kHz) call for an upgrade of the gas target technology. We report the design, implementation and testing of a novel supersonic gas jet catcher system for differential pumping in laser–plasma interaction experiments. This system allows increasing the gas load by one to two orders of magnitude, enabling continuous flow operation for the sub-mm nozzles typically used in high-repetition-rate laser wakefield accelerators. It is minimally invasive, as it is positioned a few mm above from the laser–plasma interaction; thus, it can be integrated in advanced laser accelerator beamlines that utilize complex target geometries and multiple laser pulses.

The study of matter under extreme conditions, particularly non-repeatable ultrafast processes such as those in high-energy-density physics and inertial confinement fusion, urgently demands innovations in ultrafast imaging diagnostics. To address this, we propose a novel multi-pulse, multi-angle imaging scheme that leverages a beam-splitting design applied to a single ultra-intense laser pulse to generate multiple, precisely delayed sub-pulse beams. This method not only achieves a tunable temporal resolution range from femtoseconds to picoseconds and spatial resolution in the micrometer scale, providing a powerful tool for capturing single-shot ultrafast dynamics, but also overcomes the low repetition rate limitation in petawatt-class laser facilities, enabling previously unattainable continuous dynamic imaging. Experimental validation is scheduled on the 1 PW/0.1 Hz laser system at the Shanghai Superintense Ultrafast Laser Facility. Feasibility of the source is verified by FBPIC simulations and combined with SynchRad for radiation calculations, while Geant4 simulations demonstrate imaging performance.

Dual-wavelength fiber lasers (DWFLs) hold broad promise for industrial, sensing, telecommunications and biomedical fields due to their flexible dual-wavelength emission. In this work, a DWFL architecture was numerically modeled and systematically optimized to enhance output performance. Simulation results indicated that optimizing pump power distribution, the length of the ytterbium-doped fiber and the wavelength combination can significantly improve the output characteristics. Furthermore, the incorporation of a chirped and tilted fiber Bragg grating and wider fiber Bragg gratings yields a 2.5-fold power enhancement. Guided by theoretical and experimental analysis, an output power of 31 W at 1060 nm wavelength and 840 W at 1080 nm wavelength were achieved with a signal-to-noise ratio of 32 dB. To the best of our knowledge, these represent the highest output powers reported for a DWFL to date. Our work provides valuable design insights for the development of compact, high-power DWFL systems.

The double-cone ignition (DCI) scheme optimizes laser energy coupling efficiency by decoupling the compression and heating processes. During heating, picosecond (ps) lasers are focused inside a heating cone to generate fast electrons that subsequently transport through the cone tip into high-density pre-compressed plasma and deposit their energy. The quality of fast-electron generation is critically sensitive to the inner surface condition of the heating cone tip. However, during the implosion, the continuously rising temperature and density of the colliding plasmas drive a shock wave that impacts the tip of the heating cone. A premature breakout of the tip would severely degrade the fast-electron generation and increase the beam divergence. This work experimentally investigates the shock-wave-induced cone tip breakout under DCI-relevant conditions. The results show that the shock wave breaks the cone tip later than the injection time of the ps laser and does not significantly affect the heating process.

Heat conduction in weakly collisional, magnetized plasma is challenging to model accurately due to multifaceted physics governing heat-carrying electrons, including microinstabilities that scatter electrons and modify heat transport. Capturing these effects requires multidimensional kinetic theory simulations, which are computationally expensive. Experimental constraints overcome this issue, resulting in improved understanding of thermal transport in systems such as the intra-cluster medium of galaxy clusters, and the hot-spot in inertial confinement fusion. In this paper, we present a new experimental platform that produces a weakly collisional high-$\beta$ plasma expected to be susceptible to the whistler heat-flux instability. This platform, to be fielded on the Orion laser, enables characterization of whistler-regulated thermal conductivity. The platform design is assessed using radiation-magnetohydrodynamics simulations with the code FLASH. Simulations using three thermal conduction models predict conductivity suppression by over an order of magnitude relative to the Spitzer value at whistler saturation, demonstrating the efficacy of the platform.

High-power terahertz (THz) pulses are important for material analysis and ultrafast spectroscopy, but existing sources barely achieve high field strength and average power simultaneously. Tilted-pulse-front pumping (TPFP) improves THz conversion efficiency, but its optimal configuration is highly dependent on pump parameters. Focusing on high single-pulse energy (millijoule level) and a short pulse duration (226 fs), this study systematically evaluates two TPFP configurations: the reflective grating and echelon mirror. Experimental results show that the echelon mirror configuration achieves a 0.4% conversion efficiency and a 51.7 mW average THz power, exceeding the performance of the grating configuration, which reaches 0.26% and 41.8 mW, respectively. These results confirm that combining short pulses with the echelon mirror enhances both conversion efficiency and average THz power under high-power pumping, providing experimental guidance for high-power strong-field THz sources for material manipulation and biomedical imaging.

If a stretcher is in air and a compressor is in vacuum, then the atmospheric pressure variation by 10–20 Torr can substantially reduce peak power due to changes in the index of refraction of the air $n$. This effect is stronger the larger the stretcher dispersion, the pulse bandwidth and the angle of reflection from the first grating. For a super-Gaussian pulse, a small dispersion has approximately three times the effect on pulse power as it does on pulse duration; at the pulse stretching by 5% the power reduces by 15%. By placing the stretcher in a hermetic chamber one can not only eliminate this parasitic effect but also control dispersion without mechanical distortions. The change in the stretcher/compressor dispersion caused by changes in n may be compensated for in all dispersion orders by varying the angle of incidence in a plane orthogonal to the diffraction plane.

Applications of terawatt-class lasers can enormously benefit from pulse trains with kHz repetition rates. The associated unprecedented combinations of peak and average powers require the development of new concepts for scalable ultrashort pulse generation. Through comprehensive simulations, we analyze spectral broadening of 300-ps, 100-mJ pulses in multi-pass cells and anti-resonant hollow-core fibers towards the fs regime. We introduce an 11-mirror cell geometry that can deliver kilometer-scale nonlinear interaction lengths. We experimentally demonstrate nearly 300 passes in such a cell. This enables at least four times larger B-integral to peak power ratios than in previously reported spectral broadening experiments with air-filled multi-pass cells. These results highlight the strong potential of advanced multi-pass cell designs to reach unprecedented broadening factors. The proposed scheme can efficiently transform industrially mature high-power, high-energy lasers into unique ultrafast sources.

High-repetition-rate and high-stability short-pulse lasers have broad application prospects in large-scale integrated equipment serving industrial manufacturing and scientific research. Pulse compression techniques based on transient stimulated Brillouin scattering (SBS) are an effective means of obtaining short-pulse lasers. The transient effects and thermal breakdown enhancement effects in the high-repetition-rate transient SBS process will cause significant gain attenuation, resulting in a decrease in output energy reflectivity and stability. In this study, we proposed a pulse compression technique based on transient self-pumped Brillouin scattering (SPBS). By combining pump intensity attenuation with gain compensation based on a self-feedback seed model, the transmission loss and sound field intensity fluctuations during scattering were significantly reduced. The experiment verified the compression capability of the transient SPBS, which improved the output energy reflectivity and stability. The results showed that at a repetition rate of 300 Hz, the transient SPBS had a maximum energy reflectivity of 96.5% and an output energy of 24.1 mJ. Without the interference of the breakdown effect, a stable pulsed laser output with an energy relative standard deviation of only 1.42%, a time-domain duration of 225 ps and a peak power of over 100 MW was finally obtained. Our research provides a valuable reference for the generation of high-repetition-rate, high-peak-power lasers.

We show a high-slope-efficiency Ho:CaYAlO4 laser using the conventional water-cooling method. Under an L-shaped laser resonator cavity with an overlapping efficiency greater than 98%, a maximum output power of 18.64 W at 2081 nm was achieved when the absorbed pump power was 26.83 W. By linear fitting, the slope efficiency relative to the absorbed pump power is 90.6%. Under the maximum output power, the beam quality factor is lower than 1.25 and the root-mean-square stability is about 0.42%. In addition, we validated the output performances of the laser in acousto-optic Q-switched mode under the high-slope-efficiency condition. At a pulse repetition rate of 10 kHz, the maximum average output power of 18.26 W and the narrowest pulse width of 40.1 ns were achieved, corresponding to a pulse energy, peak power and slope efficiency of 1.83 mJ, 45.54 kW and 87.7%, respectively. To the best of our knowledge, this laser may have the highest slope efficiency for a Ho-doped solid-state laser using conventional water-cooling.

Transverse mode instability (TMI) critically limits the power scaling of high-brightness fiber lasers. While recent experiments have empirically demonstrated that the TMI threshold can be significantly enhanced by temporal modulation, the fundamental physical mechanism governing this stabilization remains unknown, preventing the rational design of high-power systems. Here, we present a comprehensive numerical framework that incorporates nonlinear optical effects into the analysis of TMI dynamics under temporal modulation. We identify self-phase modulation as the dominant stabilizing mechanism, which generates a chaotic thermal grating to suppress resonant energy transfer between the fundamental and higher-order modes, thereby disrupting the TMI process. Building upon this insight, we derive a quantitative, predictive model that directly links modulation parameters and fiber properties to the TMI threshold. This work provides the missing physical foundation for understanding nonlinear TMI suppression and offers a powerful, predictive design tool for overcoming the power-scaling bottleneck in next-generation fiber laser systems.

We report on a high-energy, all-fiber nanosecond laser system seeded by a laser diode driven by 1.3 kHz electrical pulses and pumped by a 10 Hz synchronized pulsed pumping scheme. In the main amplifier, two stages of M-type 100-μm-core-diameter Yb-doped fibers (YDFs) were employed for mode homogenization, followed by the final amplification stage utilizing a 200-μm high-absorption YDF. A maximum pulse energy of 81 mJ and a peak power of 12.1 MW were achieved, corresponding to a slope efficiency of 34.2%. Notably, no significant stimulated Raman scattering component was observed in the output spectrum. The entire system featured an all-fiber-based architecture equipped with a low-repetition-rate pulse-picking amplification system. To the best of our knowledge, these results represent the highest peak power and pulse energy reported currently for a low-repetition-rate nanosecond all-fiber-based master oscillator power amplifier laser operating at 1064 nm.

The optics roughness in Öffner stretchers has been widely identified as a major cause of temporal contrast degradation at tens of picoseconds before the main pulse. However, we find that amplifier-induced noise may become the decisive factor for temporal contrast deterioration at a similar time window with the increase of the B-integral in chirped-pulse amplification systems. Even employing a high-precision convex mirror with root-mean-square roughness values better than 0.2 nm, the experimental measurements show that amplifier-induced noise generates asymmetric profiles under nonlinear effects – exhibiting an obvious pre-pedestal growth proportional to the accumulated B-integral. Analogous to post-to-pre-pulse conversion dynamics, the numerical simulations demonstrate the impact of the B-integral on the pre-pedestal, especially when the pulse peak power scales from the terawatt level to the petawatt level.

We demonstrate a fiber-based deep-ultraviolet (DUV) source at 259.4 nm delivering sub-picosecond pulses with high average power in both 81.25 MHz continuous pulse train and burst-mode operation. Based on ytterbium-doped photonic-crystal fiber amplification, we achieve over 200 W infrared laser output, followed by second-harmonic generation in lithium triborate and fourth-harmonic generation (FHG) in cesium lithium borate (CLBO). At 81.25 MHz, a maximum DUV output power of 21.7 W is obtained. With burst operation, we investigate the high-power FHG performance of the CLBO crystal under varying burst energies and average powers, and optimize the FHG configuration for different burst repetition rates. At a burst repetition rate of 300 kHz, a maximum DUV burst energy of 68 μJ is achieved, and the average power reaches 25.1 W at 750 kHz, representing the highest reported average power from an all-fiber laser source in this wavelength band.

In this work, we demonstrate a high-energy regenerative amplifier based on a single Yb:CaGdAlO4 (Yb:CALGO) crystal, delivering a pulse energy of 11.2 mJ at a 1 kHz repetition rate. To the best of our knowledge, this represents the highest pulse energy directly obtained from an Yb:CALGO single-crystal regenerative amplifier to date. To mitigate the severe gain narrowing typically associated with high-energy amplification, a specially designed polarization-spectral filter was integrated into the system to pre-shape the seed spectrum, enabling an amplified full width at half maximum spectral bandwidth of 10.1 nm. As a result, the amplified pulses were able to be compressed to a pulse duration of 198 fs without any pedestal. The output power stability, measured over 200 minutes, exhibited a root mean square fluctuation of 0.27%, and the beam quality factors were Mx2 = 1.08 and My2 = 1.17.

We investigated laser-driven shock propagation in low-density foams through coordinated experiments and simulations. At the Vulcan laser facility, a nanosecond laser pulse launched a shock from a plastic ablator–titanium pusher assembly into a 0.1 g cm–3 trimethylolpropane triacrylate foam, diagnosed by side-on, time-resolved X-ray radiography using a picosecond Cu backlighter. This enabled direct tracking of the pusher motion and the shock front. Comparison with one-dimensional and two-dimensional hydrodynamic simulations (MULTI and FLASH) shows good agreement when assuming an effective on-target intensity of (3–5) × 1013 W cm–2, lower than nominal laser estimates, underscoring the influence of coupling losses. An analytical model based on impedance-matched shock relations connects the ablation pressure, pusher dynamics and transmitted shock strength. Overall, the combined results indicate that the foam behaves as an effectively homogeneous medium under these conditions, supporting modelling assumptions for foam-based fusion targets and establishing a validated platform for future shock-propagation studies in low-density materials.

We present a finite-difference time-domain framework for modeling femtosecond (fs) to sub-picosecond (ps) laser interactions in hybrid multilayer optical coatings. A total-field/scattered-field formulation injects obliquely incident, transversely Gaussian pulses without prescribing a full initial field profile, enabling stable simulations beyond the sub-100-fs regime. The material response incorporates Keldysh photoionization and impact ionization described by a multiple-rate equation model, accurately capturing carrier multiplication in wide-bandgap dielectrics. The generated carriers are coupled to a Drude model whose collision frequency evolves in time through the electron temperature, providing a unified description of the optical response in both dielectric and metallic layers. The framework is applied to a hybrid SiO2/HfO2/Au grating irradiated by a 1057 nm, 500 fs pulse. Simulated carrier density and absorbed energy density predict laser-induced damage thresholds in very good agreement with the experiment. The approach is general and applicable to pulse durations from 10 fs to 1 ps.

A spot analysis system based on an improved YOLOv8-seg model was developed for high-power laser facilities to meet the urgent need for fast and precise positional control of optical components throughout the entire laser chain. The system addresses the inefficiency of traditional manual or semi-automatic methods when aligning numerous beamlines. An enhanced segmentation model (mean average precision@0.5 = 0.901) was constructed to recognize and extract various spot types. A multi-reference center detection mechanism was designed, achieving a positioning error of 1.9 pixels and a success rate of 98.7%, thereby improving centering accuracy and robustness in complex imaging scenarios. The system automates spot center location, morphological analysis and offset calculation with efficient processing speed to satisfy the real-time alignment demand of the facility. It outputs pixel/μm-level offset values, adjustment step size, step count and direction as structured decision parameters, providing actionable inputs for the closed-loop control of motorized actuators in rapid laser alignment.

The presented experiment aims to investigate the effects of applying an external magnetic field on laser–target interaction, hot electron generation and propagation in the target, and ultimately on the shock dynamics. The magnetic field strength was set at 20 T, which is sufficient to divert hot electrons and hinder their propagation toward a copper fluor layer. The experiment yielded a non-intuitive result, showing an equal or higher K${}_{\alpha }$ emission from the magnetized target compared with the unmagnetized one. Through extensive analysis using magnetohydrodynamics, particle-in-cell (PIC) and hybrid-PIC simulations, we found that a possible explanation is an increase in the average hot electron energy in the presence of the magnetic field. This higher energy allows the hot electrons to reach the fluor layer and produce a K${}_{\alpha }$ yield comparable to that of the unmagnetized target.