We demonstrate real-time wavefront correction in a high-energy high-average-power DiPOLE100/Bivoj laser using adaptive optics. A bimorph deformable mirror and a Shack–Hartmann wavefront sensor reduced wavefront error 10-fold and improved the Strehl ratio 11-fold. Design aspects such as the deformable mirror actuator geometry, optimal placement and loop frequency are discussed for integration into next-generation high-energy high-average-power lasers.

Femtosecond laser-induced filamentation typically exhibits pronounced spectral broadening, featuring a bright central white core encircled by concentric colored rings that span from the ultraviolet to the visible range and extend into the infrared. While ionization, self-steepening and self-phase modulation are widely accepted as explanations for the white spot, the underlying physics of colored rings remain inadequately understood by current models, such as Cherenkov radiation and four-wave mixing. In this study, inspired by the observation of similar discrete colored rings produced by cascaded four-wave mixing (CFWM) of intersecting beams, we systematically investigated the relationship between the colored rings in the white-light supercontinuum and CFWM. The CFWM model accurately predicted the correlation between color and divergence angles, thereby enhancing our understanding of spectral broadening in filamentation and providing guidance for optimizing the conversion efficiency and configuration of multi-wavelength ultrashort optical pulses in both spatial and spectral domains.

High-power laser beamlines typically operate with fixed focusing conditions, limiting the focal spot size and peak intensity. To mitigate these restrictions, prior studies used curved plasma mirrors to adjust the F-number to a specific value. Here, a double-plasma-mirror (DPM) system including spherical optics in a telescope configuration is implemented to adapt the F-number of a multi-petawatt (PW) laser beam resulting in adjustability within a range of intensities. The system is optimized to minimize focal aberrations. A dedicated imaging system is used to evaluate focus quality and the DPM reflectivity at the multi-PW level. Temporal contrast enhancement of the reflected beam is additionally demonstrated, as evidenced by higher particle yield and proton kinetic energy from nanometer-thick foils, compared to results without DPMs. These findings enable multi-PW laser facilities to explore more extreme laser–plasma conditions that require ultra-high temporal contrast and intensity, while expanding their capabilities in intensity adjustment beyond designed specifications.

We present an experimental study of proton acceleration driven by femtosecond multi-PW lasers of three different prepulse parameters with the peak laser intensity of 1.2 × 1021 W/cm2 irradiating micrometre-thick metal foils. For 4-μm-thick copper foils, the highest-energy proton beam of 58.9 MeV is generated with the moderate-contrast laser, while the low-contrast or high-contrast lasers result in the lower proton cutoff energies. The one-dimensional hydrodynamic and two-dimensional particle-in-cell simulations indicate that the front preplasma of foils induced by the laser prepulse can enhance electron acceleration and in turn improve proton acceleration, while the rear preplasma will weaken the sheath field and be unfavourable for accelerating ions. For the case of the moderate contrast, the scale length of the front preplasma is long enough to generate high-temperature electrons compared to the high-contrast case, and the scale length of the rear preplasma is so short that the sheath field still remains strong compared with the low-contrast case, which is advantageous for generating high-energy protons. Meanwhile, a concrete map is theoretically given for accelerating higher-energy protons. This work extends the concept of the prepulse effect on target normal sheath acceleration (TNSA) to a wider range of laser parameters (multi-PW, 1021 W/cm2), representing an important step towards potential applications of TNSA-driven proton sources, especially considering that PW and even 10 PW laser facilities exist all around the world.

We demonstrate a high-efficiency, high-power Er:CaF2 single-crystal fiber (SCF) continuous-wave (CW) laser pumped by a 976 nm laser diode. By carefully analyzing the thermal lensing effect and optimizing mode matching, we achieved a maximum CW output power of 10.02 W, corresponding to a slope efficiency as high as 32.2% for pump power below 25 W. To the best of our knowledge, this represents the highest output power ever reported for 2.8 μm SCF lasers, approximately an order of magnitude higher than previous results. In addition, a wavelength redshift beyond 2.8 μm was observed at high power, extending beyond the strong absorption region of water vapor. These results indicate that Er-doped CaF2 SCFs are promising candidates for high-power mid-infrared lasers.

A 2.05 μm holmium-doped yttrium lithium fluoride (Ho:YLF) master oscillator power amplifier system with both high average power and high pulse energy operating at a 1 kHz repetition rate is demonstrated, achieving a maximum output power of 280 W with a pulse width of 14.5 ns. The system comprises three-stage amplifiers, boosting a 20 W seed laser to output powers of 110, 205 and 280 W, corresponding to extraction efficiencies of 46.1%, 45.0% and 34.9%, respectively. At maximum output, the system exhibits excellent beam quality (Mx2 = 1.22 and My2 = 1.23) and power stability (root mean square = 0.5% over 30 min). To the best of our knowledge, this work reports the highest pulse energy (280 mJ) achieved for a 2 μm laser operating at a kHz repetition rate. In addition, a slice model of an end-pumped quasi-three-level laser amplifier was developed to analyze the output limitations of multi-stage Ho:YLF amplifiers based on rod geometry, providing theoretical support for the experimental results.

We demonstrate a high-power, flexibly tunable dual-pulse laser via temporal modulation techniques to overcome conventional systems’ fixed pulse width and temporal interval constraints, enhancing precision micro/nanofabrication and nonlinear photonics applications. By combining dispersion-engineered seed pulse shaping for adjustable pulse widths (5.6 ps and 0.38–0.47 ns) with optical-delay synchronized interval tuning (from –4 to 12.5 ns), the system achieves wide flexibility in pulse configuration. Furthermore, detailed nonlinear dynamics studies reveal the picosecond component exhibits reduced amplifier efficiency versus the nanosecond component, primarily due to peak-power-driven irreversible energy transfer to Raman-shifted wavelengths. This unique combination of features enables remarkable performance: 1092 W average power at 16 MHz with precisely tailored 15.9 ps/0.44 ns pulse widths and 4.2 ns temporal interval. This high-power tunability establishes a transformative material processing paradigm from precision machining to photonics, advancing fundamental nonlinear pulse science and setting new industrial laser standards.

The ELI ERIC facility offers international users ultrashort laser sources via the ALPS facility focusing on few-cycle laser drivers for attosecond pulses, particle beams and ultrahigh intensity interactions. The HR1 system supports attosecond high harmonic generation (HHG) and time-resolved spectroscopy at 100 kHz. However, its high repetition rate, while aiding statistical analysis, poses thermal challenges and limits certain applications requiring lower repetition rates. To address this, the HR Alignment laser system was developed for the HHG beamline at the ELI-ALPS facility. This new system delivers sub-6 fs, 1 mJ pulses with a tunable repetition rate (from 10 Hz to 10 kHz) and carrier-envelope phase (CEP) stabilization. It utilizes an ytterbium-doped potassium gadolinium tungstate front-end, multi-pass cell compression, and chirped mirrors. Characterization confirms excellent energy and CEP stability (below 300 mrad), beam quality and temporal contrast, matching the HR1 laser’s performance. This compact, stable system provides high-flux attosecond generation for reaction microscopy enhancing ultrafast research in the ELI-ALPS facility.

We report a record-breaking 213.4 W continuous-wave diamond Raman laser operating at 1240 nm using polarization beam combining dual-fiber pumps and a quasi-Z-shaped cavity to suppress back-reflection. The secondary pump amplified the Stokes field without altering its polarization, confirming polarization-independent gain enhancement. Results demonstrate that high pump power, robust cavity design, reduced optical damage, temperature control of the mirror and crystal and parasitic Brillouin suppression were critical for maximizing Stokes output. The work surpasses the decade-old 154 W record, highlighting diamond’s potential in high-power applications.

Spectral coherent combining (SCC) offers a powerful approach to increase output power and shorten pulse duration. Here, we comprehensively investigate SCC of two beams to achieve the high combining performance. The preliminary analysis indicates that incident spectra and the transition region of the combiner both affect the combining process. The simulation results show that optimizing the overlapping spectral range, the transition width and start wavelength of the combiner can achieve high combining efficiency and high pulse quality. Guided by the simulation results, we built a femtosecond laser system based on the SCC of two fiber amplifiers, achieving 96.9% combining efficiency and high-quality 42-fs pulses. To the best of our knowledge, this is the first time that high combining efficiency and high pulse quality have been achieved simultaneously in a fiber femtosecond laser system based on SCC. This study provides design guidelines for the high-performance combination of beams covering different spectral regions.

We report the generation of intense deep ultraviolet pulses at 200 nm with a duration of 48 fs and a pulse energy of 130 μJ, achieved via cascaded sum-frequency generation using 800 nm femtosecond pulses in barium borate crystals. Efficient frequency up-conversion is realized by optimizing phase-matching conditions and implementing dispersion control, while maintaining the ultrashort pulse characteristics. The generated deep ultraviolet pulses are characterized using two-photon absorption frequency-resolved optical gating, providing detailed insight into their temporal profile and phase. This approach addresses key challenges in ultrashort deep ultraviolet pulse generation, delivering a high-energy, ultrashort source suitable for ultrafast spectroscopy, nonlinear optics and strong-field physics. These results represent a significant advancement in the generation of high-energy, ultrashort deep ultraviolet pulses, opening up new possibilities for time-resolved investigations in ultrafast molecular dynamics, as well as emerging applications in semiconductor science, quantum materials and photochemistry.

We present time-dependent two-dimensional (2D) and three-dimensional (3D) fluid simulations of a gas cell with a variable length of 0–5 cm, designed for laser wakefield acceleration. The cell employs an output nozzle producing extended density ramps, which can facilitate the production of high-quality electron beams. In both geometries, the simulations demonstrate uniform density inside the cell. In the 3D case, the mean density inside the cell reaches a density nonuniformity below $1\%$ after 100 ms. The density equilibrium time, $\tau$, scales with the ratio of cell volume-to-outlet area, a relationship that is not captured by the 2D simulations showing five times shorter equilibrium time. We present a method to determine $\tau$ from fluid simulations, allowing the estimation of the minimum delay required to enable a uniform target density. Such uniformity prevents uncontrolled electron injection from density ripples, which has direct implications for optimizing beam quality and reproducibility in wakefield acceleration.