Surface defects on fused silica optics significantly limit their laserinduced damage resistance under ultraviolet pulsed laser irradiation, yet a quantitative correlation between defect parameters and damage thresholds remains 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 m wide) have DOFs of 1.27-13.2J/cm 2 , while plastic continuous scratches (0.4-5.8 m wide) exhibit

Power scaling of neodymium (Nd)-doped single-frequency fiber lasers (SFFLs) operating at ~900 nm has been fundamentally constrained by dominant ~1060 nm emission, with previous demonstrations limited to below 3 W. Here, we demonstrate a 910 nm single-mode Nd-doped SFFL system that achieves a record over 30 W output power employing homemade Nd-doped silica fiber (NDF), while preserving exceptional 49 dB suppression of competing ~1060 nm emission.The laser system originates from a distributed Bragg reflector (DBR) single frequency (SF) oscillator with 11 mW output power, which is subsequently amplified to 31.1 W through three polarizationmaintaining (PM) amplification stages utilizing PM 10/125 m 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 (Mx=1.03,My=1.05) and narrow linewidth (10.2 kHz).These results validate that the homemade PM 10/125 m NDF can be employed in intermediate and main amplifier in all-fiber SF master oscillator power amplifier (MOPA) system at ~900 nm.

Abstract LiGaS 2 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 LiGaS 2 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.

Abstract The double-cone ignition scheme is a promising novel ignition method, which is expected to greatly save the driver energy and enhance the robustness of the implosion process. In this paper, ablation of the inner surface of the cone by the hard X-ray from coronal Au plasma is studied via radiation hydrodynamics simulations. It is found that the X-ray ablation of the inner wall will form strong pre-plasma, which will significantly affect the implosion process and cause the Au plasma to mix with the fuel, leading to ignition failure. The radiation and pre-ablation intensities in the system are estimated, and the evolutions of areal density, ion temperature and the distribution of Au ions are analysed. In addition, the mixing of Au in CH at collision is quantified. Then, a scheme to reduce the X-ray pre-ablation by replacing the gold cone with a tungsten cone is proposed, showing that it is effective in reducing high-Z mixing and improving collision results.

Abstract Recent advances in high-power, high-repetition-rate laser systems are driving the adoption of data-driven experimental approaches in high-energy density science. To fully realize the potential of these methodologies, automated and high-throughput analysis of key diagnostics is essential for effective feedback and real-time optimization. We present a novel algorithm, ARISE (algorithm for rapid ion spectrum extraction), developed for fast and reliable extraction of laser-accelerated ion spectra from Thomson parabola spectrometers, capable of operating at repetition rates exceeding 20 Hz. ARISE enables real-time, data-driven experimentation through features including background subtraction, automatic identification of the zero-deflection reference point and automated determination of maximum ion energy. We validate the accuracy of ARISE in spectrum extraction and energy detection, and demonstrate its integration within a Bayesian optimization framework during a proof-of-concept experiment conducted using the 350 TW SCAPA laser, enabling real-time optimization of laser-accelerated ion beam parameters.

Abstract We demonstrate a high-efficiency, high-power Er:CaF 2 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 CaF 2 SCFs are promising candidates for high-power mid-infrared lasers.

Abstract A broadband, antireflective metasurface optic on a silica substrate is subjected to laser-induced damage-threshold measurements to quantify its performance under exposure to high-intensity/fluence laser pulses in the near-infrared at four pulse durations, ranging from 20 fs to 1.4 ns. The performance of the metasurface is benchmarked against that obtained from an equivalent bare fused-silica substrate that did not receive reactive-ion-etching metasurface treatment. Results showed that the damage threshold of the antireflective metasurface was always lower than the input-surface damage threshold of the untreated substrate. The damage initiations with nanosecond and picosecond pulses resulted in localized modification and removal of the nanostructures, whereas the onset of laser-induced modification with 20-fs pulses in a vacuum environment manifested as changes in the optical and electronic properties without significant material removal. The broader goal of this work is to develop a preliminary understanding of the laser-induced failure mechanisms of silica-based metasurface optics.

Abstract We demonstrate a Yb:CaGdAlO 4 (Yb:CALGO) bulk regenerative amplifier (RA) capable of delivering a peak power of 0.112 TW at a 1 kHz repetition rate. By integrating a home-built ultrabroadband nonlinear polarization evolution (NPE) mode-locked fiber oscillator, a set of custom-designed spectral shapers and the broad emission bandwidth Yb:CALGO gain medium, an amplified bandwidth of 18.2 nm and an output pulse duration of 137 fs are achieved. Thanks to the thermally insensitive dual-crystal cavity design and the quasi-continuous pumping thermal management scheme, the RA achieves a maximum pulse energy output of 21.01 mJ. Under the constraint of avoiding crystal damage, the compressed pulse energy reaches 17.6 mJ. To the best of our knowledge, this represents the highest pulse energy and peak power ever achieved from a Yb:CALGO RA. The power stability over 30 minutes is measured to be 0.506%, and the beam quality factor M 2 is 1.16 × 1.12.

Abstract A dual-beam platform is developed for all-optical Thomson/Compton scattering, with versatile parameter tuning capabilities including electron energy, radiation energy, radiation polarization, etc. By integrating this platform with a 200 TW Ti:sapphire laser system, we demonstrate the generation of inverse Compton scattering X-/gamma-rays with tunable energies ranging from tens of keV to MeV. The polarization of X-/gamma-rays is manipulated by adjusting the polarization of the scattering laser. In the near future, by combining this platform with multi-PW laser facilities, our goal is to explore the transition from nonlinear Thomson scattering to nonlinear Compton scattering, ultimately verifying theories related to strong-field quantum electrodynamics effects induced by extreme scattering.

Abstract The effect of the polarizations of two counter-propagating relativistic laser pulses interacting with subwavelength thin solid-density foil is investigated. Three-dimensional particle-in-cell simulations and analytical modelling show that the interaction and resulting transverse instability depend strongly on the polarization directions as well as the intensity distribution of the resultant light field in the foil. The left- and right-handed circularly polarized laser pair with the same phase at the common focal spot in the ultrathin foil leads to the strongest distortion of the foil. The fastest growing mode and maximum growth rate depend mainly on the laser intensity. For all polarization and phase-difference combinations, the instability is weakest when the two laser pulses are exactly out of phase at the common focusing point in the foil.