Despite considerable progress in multi-stage laser wakefield acceleration (MSLWFA), efficient coupling between stages and the impact of laser-beam injection delay remains open challenges. A two-stage LWFA scheme is demonstrated using particle-in-cell (PIC) simulations, capable of producing multi-GeV electron beams over millimeter-scale propagation lengths. In the first stage, a high-intensity laser pulse (with [Formula: see text] [Formula: see text], [Formula: see text]= 800 [Formula: see text] and [Formula: see text]) propagates through a neutral helium (He) gas target inside a gas cell, with ionization modeled self-consistently to produce a fully ionized plasma at a plateau density [Formula: see text], generating a high-quality 1 GeV electron beam. This beam is then injected into a second stage inside the same gas cell, where systematically varying the injection delay enhances the injected bunch energy to 2.5 GeV and boosts background trapped electrons to 3 GeV, while reducing energy spread and preserving charge. These findings underscore the critical role of synchronization and plasma tailoring strategies relevant for future multi-pulse and flying-focus LWFA configurations.

Abstract Laser wakefield acceleration offers ultra-high accelerating gradients, enabling compact sources of multi-GeV electron beams with femtosecond duration and quasi-monoenergetic spectra. In this work, we investigated the nonlinear evolution of plasma bubbles and their effect on electron injection and energy gain, using high-fidelity, multi-dimensional particle-in-cell (PIC) simulations performed with the open-source code SMILEI. A relativistically intense laser pulse (a 0 =7.7, λ 0 =0.8 μm, w 0 =20 μm, E=30 J, and τ=30 fs) propagated through a helium gaseous medium with a plateau density of n e =7×10 18 cm -3 after complete ionization. The simulations revealed complex bubble dynamics, including initial formation, disruption, destruction, and bubble merging, strongly influenced by local longitudinal electric field E x approaching or exceeding the cold wave-breaking limit E WB . Exceeding the wave-breaking field E WB triggered bubble destabilization, while the bubble merging at the end of the plateau plasma density region extended the acceleration length, sustaining high longitudinal fields on the order of 1 TV/m and boosting continuous electron injection. This mechanism produced a dense, quasi-monoenergetic electron bunch with a charge of 1 nC, a peak energy of ~1 GeV, femtosecond-scale duration, energy spread below 10%, rms angular divergence θ y of 7 mrad, and a longitudinal rms beam size of σ x =10 μm. Comprehensive analysis of the wakefield structure evolution demonstrated that exploiting nonlinear bubble evolution and interactions near the wave-breaking limit can enhance both energy gain and electron beam quality, providing actionable strategies for next-generation compact LPAs.

To achieve accurate temporal characterization of broadband laser pulses, a sufficient phase-matching bandwidth is required. The problem is mainly solved by using third-order nonlinear effects or few-micrometer-thin secondorder nonlinear crystals. However, difficulties persist in enhancing signal conversion efficiency while ensuring sufficient bandwidth. In this work, we propose a bandwidth-extending method based on spectral filtering function and ptychographic algorithm, termed Spectral Correction and Trace Truncation (SCTT), for characterizing broadband pulses. In experiments, we achieved the characterization of 720-880 nm broadband pulses using a beta-barium borate (BBO) crystal with a thickness of up to 100 mu m-far beyond the scale of a few microns-under phase-matching configuration. The reconstructed pulses are consistent with the standard results obtained using a 5-mu m-thin BBO crystal, but the measurement sensitivity and signal-to-noise ratio are increased by a factor of similar to 18, and the minimum measurable pulse energy is less than 10 pJ.

The wide-field spiral phase contrast microscope (SPCM) is an all-optical edge-enhanced imaging technique that performs Fourier filtering based on a 4f system. It allows large phase gradients to be highlighted through convolution of a phase object with the point spread function (PSF) given by the Fourier transform of the coherent transfer function (CTF). In the case of pupil mismatch between the 4f system and the spiral phase filter (SPF) placed at the Fourier plane, the physical edge diffraction of the SPF is non-negligible and will cause strong sidelobes in the PSF, leading to low image resolution and background noise after convolution. Herein, we propose a scanning SPCM, which uses an Airy spot to sample the phase object laterally point by point and detects the on-axis intensities at the image plane accordingly. This structural change transforms the SPCM from Fourier filtering to match filtering. Match filtering allows the SPCM to optically compute the complex weight that measures the matching degree between the Fourier transform of the local sampled field of the phase object and the joint CTF, which is the convolution of the illumination pupil and the imaging pupil. The edge enhanced image is directly given by the complex weights at the sampling coordinates. The scanning SPCM takes the advantage of the joint CTF, which not only shows a much higher cutoff spatial frequency than the wide-field SPCM, achieving high-resolution imaging, but also shows soft edges, achieving suppressions of physical edge diffraction of the SPF and sidelobes in the joint PSF. The imaging results of phase objects verified that the scanning SPCM achieves twofold resolution improvement. The scanning SPCM breaks through the inherent barrier of low image resolution in the wide-field SPCM by transforming Fourier filtering to match filtering, and it possesses great advantages in all-optical high-resolution edge enhancement.

Vortex dynamics are intriguing and challenging across multiple physics fields. In optics, customized spatiotemporally structured optical fields, especially spatiotemporal optical vortices (STOV), offer the potential to tailor light via coupled space-time degrees of freedom. However, the interaction mechanisms between multiple transverse orbital angular momentum singularities within a single wave packet remain elusive. This study explores the intrinsic dynamics of a STOV with three phase singularities, observing a pronounced vortex singularity oscillation phenomena by tuning the temporal dispersion. We show that these phenomena originate from the counterintuitive spatiotemporal attractive effect between vortices, which is closely related to the singularity distance. Furthermore, the stretching into filaments and annihilation behaviors is observed by introducing antivortex in the center of the wavepacket. Experimentally, we propose a Full Interferometric Retrieval of Spatiotemporal Tomography (FIRST) method that enables the complete, single-shot capture of wave packets, with excellent agreement between theoretical predictions and experimental results. To the best of our knowledge, the dynamics of transverse spatiotemporal singularities within a single wave packet are reported here for the first time. These findings confirm the existence of interesting interactions between STOV singularities, deepen our understanding of photonics and open a new direction for investigating the complex dynamics of vortex singularities in the spatiotemporal domain.

Laser-driven particle acceleration and related laser-matter interaction experiments require an ultrashort pulse laser with high temporal contrast. Here, we presented a plasma mirror (PM) temporal contrast enhancement system implemented at the SG-II 5PW laser facility, with a comprehensive investigation of spatiotemporal properties and physical applications. Key performance parameters of a PM were successfully obtained through single-shot online measurement by combining a spatiotemporally overlapped chirped pulse method. At a 45° incidence angle, the plasma reflectivity reached 84% for S-polarization and 48% for P-polarization, while the focal spot maintained excellent quality and the temporal contrast was improved by two orders of magnitude. The PM system was further applied in proton acceleration experiments under both polarization configurations. Supported by corresponding physical diagnostics, a significant reduction in optimum target thickness from 8 to 0.8 μm was achieved-clear evidence of effective pre-pulse suppression. Additionally, the PM and target installation were evaluated using a triple laser-damaged imaging method, based on the analysis of the three PM damage spots.

The suppression of ablative Rayleigh-Taylor instability (ARTI) by a spatially modulated laser in inertial confinement fusion (ICF) is studied through numerical simulations. The results show that in the acceleration phase of ICF implosion, the growth of ARTI can be suppressed by using a short-wavelength spatially modulated laser. The ARTI growth rate decreases as the wavelength of the spatially modulated laser decreases, and ARTI is completely suppressed after a certain wavelength has been reached. A spatially uniform laser is introduced to keep the state of motion of the implosion fluid consistent, and it is found that the proportion of the spatially modulated laser required for complete suppression of ARTI decreases as the wavelength continues to decrease. We also optimize the spatial intensity distribution of the spatially modulated laser. In addition, as the duration of the spatially modulated laser decreases, the proportion required for completely suppressing ARTI increases, but the required energy decreases. When the perturbation wavenumber decreases, the wavelength of the spatially modulated laser required for complete suppression of ARTI becomes longer. In the case of multimode perturbation, ARTI can also be significantly suppressed by a spatially modulated laser, and the perturbation amplitude can be reduced to less than 10% of that without a spatially modulated laser. We believe that the conclusions drawn from our simulations can provide the basis for new approaches to control ARTI in ICF.

Coherent combining of several low-energy few-cycle beams offers a reliable and feasible approach to producing few-cycle laser pulses with energies exceeding the multi-joule level.However,time synchronization and carrier-envelope phase difference(ΔCEP)between pulses significantly affect the temporal waveform and intensity of the combined pulse,requiring precise measurement and control.Here,we propose a concise optical method based on the phase retrieval of spectral interference and quadratic function symmetry axis fitting to simultaneously measure the time synchronization and ΔCEP between few-cycle pulses.The control precision of our coherent beam combining system can achieve a time delay stability within 42 as and ΔCEP measurement precision of 40 mrad,enabling a maximum combining efficiency of 98.5％.This method can effectively improve the performance and stability of coherent beam combining systems for few-cycle lasers,which will facilitate the obtaining of high-quality few-cycle lasers with high energy.

Objective SiO2 antireflective films prepared using a Sol-gel method are an important feature of high-power laser facilities, and a significant demand exists for third-harmonic porous SiO2 antireflective films in terminal optical components. Due to the porous nature of SiO2 antireflective films, their properties are easily affected by organic pollutants and moisture water molecules during facility operations. To ensure the basic properties of third-harmonic SiO2 antireflective films, further improving the stability of the films to reduce the replacement frequency of the third-harmonic components and increasing the overall operational efficiency of the facilities are necessary. Methods SiO2 Sol was prepared using tetraethyl orthosilicate as a precursor, ethanol as a solvent, and ammonia as a catalyst. SiO2 antireflective films with enhanced transmittance at the third harmonic were then obtained by dip-coating following SiO2 Sol dilution (Fig. 1). An optimized third-harmonic porous SiO2 antireflective film (3AR+5MR) was prepared by surface cladding with a small-particle silica Sol containing methyl groups, and its properties were compared with those of a third-harmonic SiO2 antireflective film (3AR) prepared by traditional chemical atmospheric treatment using ammonia and hexamethyldisilazane. The films were analyzed based on their optical performance, laser damage threshold performance, and environmental stability. Results and discussions The initial optical performance of the 3AR+5MR film shows that the peak transmittance is greater than 99.5% at 370 nm, which is close to that of the 3AR film (Fig. 2), and the uniformity of the films is good (Fig. 4). Although a thin layer is present on the surface of the 3AR+5MR film, it still maintains the characteristics of high porosity and achieves efficient antireflection, whereas the surface pore size tends to be more uniform (Fig. 3). The water contact angle of the 3AR+5MR film reaches nearly 120 degrees, and the change trend affected by water vapor is relatively slow because the interface layer of the 3AR+5MR film protects the porous film from the effects of water vapor better than that of the 3AR film (Fig. 5). The 3AR+5MR film is more stable than the 3AR film in terms of antipollution and moisture resistance, and the degradation of the various properties is slower (Figs. 6 and 7). The surface cladding layer can reduce the effects of organic gas molecules and water vapor molecule intrusion on the optical properties of the film. The surface roughness of the 3AR+5MR film is approximately 9 nm, which is comparable to that of the 3AR film (Figs. 8 and 9). Analysis of the laser damage performance shows that the initial zero probability laser-induced damage threshold measured by a 1-on-1 method is 18.9 J/cm(2) (3AR+5MR, 355 nm, 8.8 ns) and 19 J/cm(2) (3AR, 355 nm, 8.8 ns) (Fig. 10). Simultaneously, the preparation process time of the 3AR+5MR film is shorter than that of the 3AR film, which can effectively improve the production capacity of SiO2 antireflective films for large optical components. Conclusions A high demand exists for third-harmonic SiO2 antireflective films applied to large-aperture optical elements in high-power laser facilities. In this study, a modified third-harmonic SiO2 antireflective film with excellent properties and environmental stability was fabricated using a surface-cladding process. Results show that the preparation efficiency of the SiO2 antireflective films is significantly improved, which helps to increase the batch production capacity of SiO2 antireflective films for large optical components whenever a new large high-power laser facility is constructed.

Large-diameter K(HxD1-x)2PO4 (DKDP) crystals have been widely applied for optical parametric chirped pulse amplification and broadband UV generation in superintense ultrafast lasers and inertial confinement fusion facilities. Herein, we systematically investigated the noncritical phase-matching wavelength properties of KDP-family crystals at room temperature and demonstrated a precise characterization method for the deuterium contents of large-diameter DKDP crystals based on the similar to 245 and similar to 215 nm deep-UV sum-frequency generation (SFG). This SFG measurement method overcomes the low accuracy disadvantage of the Raman spectroscopy, especially for the DKDP crystals with deuterium contents of >90%. Full-range (0-100%) measurement with a precision of similar to 0.148% cm was achieved, which is an enhancement of more than one order of magnitude over conventional spectroscopic schemes. This work not only has the potential to be a standard method for the deuterium content characterization of DKDP crystals, but also paves the way for energy improvement and applications of tunable deep-UV radiation by fully utilizing large-diameter characteristics of KDP-family crystals.

To meet the requirements of high-speed and high-sensitivity detection of surface defects of transparent optics, and to solve the problems of the low scanning efficiency of the dark field scattering point confocal imaging and the cross-talk of the line confocal imaging, a "point-to-line" confocal collection device for dark field scattering light is designed by partially breaking the object-image conjugacy constraint of the objective. It breaks through the bottleneck of mutual restriction between numerical aperture and field of view, and greatly increases the line field of view from "millimeter" to "hundred millimeter". A high-speed laser line scanning strategy is designed to illuminate the tested surface with only one laser spot every moment, avoiding the cross-talk of the scattering light of defects. On this basis, a "point-to-line" confocal dark field laser scattering probe with optical sectioning capability is developed. The probe shows the ability of separation of the scattering light from the front and back surfaces of transparent optics. The experiments show that the effective line field of view of the probe reaches 100 mm and the scattering light collection uniformity is 80. 7%. For a transparent optical element with a thickness of 2 mm, the signal-to-noise ratio for suppressing back-surface scattered light is up to 14. 1 dB. The system has a scanning efficiency of 800 mm(2)/s at a scan speed of 8 mm/s, a lateral resolution of 20 mu m, a signal-to-noise ratio of the scattering signal of 10. 9 dB for a fine scratch with a width of 1. 16 mu m, and a figure of merit of 6. 9 cm(-2)s(-1)mu m(-1).

The advent of spatiotemporal wave packets (STWPs), represented by spatiotemporal optical vortices (STOVs), has paved the way for the exploration in optics and photonics. To date, despite considerable efforts, a comprehensive and efficient practical means to characterize wave packets with such complex structures is still lacking. In this study, we introduced a method designed to achieve high-precision and high-throughput spatiotemporal wave packet measurements using a user-friendly setup. This method is based on a quadriwave lateral shearing interferometric wavefront sensor that utilizes wavelength division multiplexing, termed the "spatiotemporal wavefront sensor (STWFS)." Using this method, we have fabricated a compact prototype with 295 x 295 spatial pixels x 36 wavelength channels of 0.5 nm spectral resolution in a single frame. This STWFS enabled single-shot self-referenced spatiotemporal three-dimensional (3D) optical field characterizations of STWPs with transverse orbital angular momenta L of 1 and 2 and obtained the dynamic visualization of the focused propagation of STOV pulses. Furthermore, the STWFS provides a 1.87 nm (0.95%) root mean square absolute accuracy for spatiotemporal phase reconstruction. The STWFS exhibits excellent comprehensive performance compared to existing 3D spatiotemporal metrology methods. As a spatiotemporal optical field characterization method, the STWFS can be applied to any type of ultra-short laser beam and offers ultrafast 3D diagnostics, contributing to spatiotemporal photonics and broader applications across different fields such as light-matter interactions and optical communications. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Significance The proposal of chirped pulse amplification (CPA) technology marked a breakthrough in the advancement of high-power laser, successfully resolving the fundamental challenge between scaling up the peak power of ultrashort pulses and avoiding optical damage. Prior to CPA, laser amplification faced a critical bottleneck: direct amplification of ultrashort pulses resulted in extremely high peak power densities, which readily induced nonlinear self-focusing within the gain medium. This not only caused optical damage but also severely limited further increases in output peak power. In 1985, Mourou and Strickland first introduced CPA, whose core principle involves dividing the amplification process into three stages-pulse stretching, amplification, and compression-thereby significantly reducing the instantaneous peak power density during amplification and effectively mitigating the risk of optical damage. With an output of 660 J in 440 fs, NOVA-PW, the world's first petawatt laser system based on CPA, was developed at the Lawrence Livermore National Laboratory (LLNL) in the United States in 1996. The system employed a large-aperture neodymium-doped glass (Nd & ratio;glass) amplifier chain, establishing the foundational architecture for picosecond petawatt laser systems. With a gain bandwidth of hundreds of nanometers, titanium-doped sapphire (Ti & ratio;sapphire) emerged as a primary gain medium in CPA for generating tens-of-femtosecond pulses, enabling the realization of femtosecond petawatt laser systems. Since the late 1990s, the integration of CPA with optical parametric amplification (OPA) has led to the development of optical parametric chirped pulse amplification (OPCPA). This approach offers advantages such as high gain, broad spectral bandwidth, and low thermal load, effectively alleviating the gain narrowing limitations inherent in conventional CPA, thus facilitating the advancement of high-power laser systems toward broader spectral bandwidth and higher peak power. Progress In recent years, the development of ultrashort pulse lasers has been driven by three primary technical approaches. The first is CPA based on Nd & ratio;glass systems, exemplified by facilities such as NIF-ARC and OMEGA-EP in the United States, LMJ-PETAL in France, Vulcan in the United Kingdom, LFEX in Japan, PHELIX in Germany, and SG-II-UP PW in China. The second is CPA employing Ti & ratio;sapphire systems, including ELI in the European Union, BELLA in the United States, CORELS in South Korea, J-KAREN-P in Japan, and SULF in China. The third is OPCPA based on nonlinear crystal systems, such as PEARL in Russia, CAEP-PW and SG-II fs Multi-PW in China. The National Laboratory on High Power Laser and Physics (NLHPLP) at the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has successively developed three ultrashort pulse laser facilities based on the SG-II platform. The sub-picosecond system (SPS), completed in 2003, was the first Nd & ratio;glass-based ultrashort pulse laser facility in China, providing critical experience for the subsequent design, construction, and operation of domestic high-power picosecond laser systems. The SG-II-UP PW facility, completed in 2014, marked the first picosecond petawatt laser system in China. Several significant physics experiments were conducted by this facility, including the world's first indirect drive fast ignition and the acceleration of 70 MeV protons. Following the expansion of the SG-II-UP facility, the capability for dual high-energy picosecond petawatt lasers to perform synchronized target irradiation was successfully established in 2024. The SG-II fs Multi-PW, developed in 2017, incorporated an amplification chain with fully non-collinear OPCPA architecture, realizing the target shooting with femtosecond petawatt laser and high-energy nanosecond laser for the first time. Conclusions and Prospects NLHPLP has taken a leading role in the research, development and application of high-power ultrashort pulse laser facilities based on CPA and OPCPA technologies in China. It has established the SG-II platform and formed a comprehensive research system of "technological breakthrough-facility development-physical application". The completion of three major facilities-SPS, SG-II-UP PW, and SG-II fs Multi-PW-has filled domestic technological gaps in high-power laser. Significant technological advances have been made in areas such as high signal-to-noise ratio (SNR) front-ends, broadband pulse amplification, laser pulse compression, and advanced ultrafast diagnostics. In physical applications, the SG-II platform has achieved multiple milestones, including the world's first indirect drive fast ignition experiment, a new national record in proton acceleration, and innovative plasma diagnostic techniques. Significant potential remains for advancing both the output capability and spatiotemporal precision control of high-power ultrashort pulse lasers. Efforts are urgently required to overcome key technical bottlenecks, including ultrashort pulse laser-induced damage, small-focal-spot beam combining for target irradiation, and ultra-high SNR control. Addressing these challenges will enable laser-target interactions characterized by higher intensities, improved coupling precision, and enhanced energy transport efficiency. Sustained research is essential in areas such as optimization of pulse compression architectures, beam quality control, and increasing the damage thresholds of optics-all of which are critical to further enhancing the performance of picosecond petawatt laser systems. To achieve high-precision beam combining for target irradiation, two core requirements must be met: first, each beam must support tight focusing with microradian level pointing accuracy and precise target positioning; second, sub-picosecond beam synchronization must be achieved. Furthermore, improving the efficiency of laser energy delivery to the target necessitates further enhancement of the SNR in picosecond lasers, as well as a critical measure to suppress target pre-ionization and the reflective effects of pre-plasma on the main pulse. The development of ultrashort pulse lasers is undergoing a shift, from a primary focus on fundamental scientific research driven by peak power as a singular metric toward meeting the demands of engineering applications that require simultaneous high peak power and high average power. This transition is driving the evolution of laser systems from traditional single-shot operation to stable, high-repetition-rate operational regimes. Petawatt lasers featuring high efficiency, high energy output, and high repetition rates not only represent a major leap in laser performance but also catalyze systematic innovation across enabling technologies, including new laser gain materials, high-quality optics and new-generation amplification system. Meanwhile, high-repetition-rate petawatt lasers are progressively transforming high-energy-density physics research, providing new momentum for disciplinary advancement through the deep integration of cutting-edge technologies such as artificial intelligence.

Laser-driven inertial confinement fusion (ICF) diagnostics play a crucial role in understanding the complex physical processes governing ICF and enabling ignition. During the ICF process, the interaction between the high-power laser and ablation material leads to the formation of a plasma critical surface, which reflects a significant portion of the driving laser, reducing the efficiency of laser energy conversion into implosive kinetic energy. Effective diagnostic methods for the critical surface remain elusive. In this work, we propose a novel optical diagnostic approach to investigate the plasma critical surface. This method has been experimentally validated, providing new insights into the critical surface morphology and dynamics. This advancement represents a significant step forward in ICF diagnostic capabilities,with the potential to inform strategies for enhancing the uniformity of the driving laser and target surface, ultimately improving the efficiency of converting laser energy into implosion kinetic energy and enabling ignition.

For accurately characterizing broadband laser pulses, an ample phase-matching bandwidth is required. This is primarily addressed through the employment of third-order nonlinear effect or few-micrometer-thin second-order nonlinear crystals. However, there are still challenges in enhancing signal conversion efficiency while ensuring sufficient bandwidth. In this study, we introduced a bandwidth-extending method utilizing spectral filtering function and ptychographic algorithm, called Spectral Correction and Trace Truncation (SCTT), for broadband pulse measurement. Experimentally, we successfully characterized 160-nm-wide broadband pulses at a center wavelength of 800 nm through Second Harmonic Generation-Frequency Resolved Optical Gating (SHG-FROG) with a 100-mu m-thick beta-barium borate (BBO) crystal in phase-matching configuration. Its reconstructed pulses are in line with the standard results obtained using a 5-mu m-thin BBO crystal, but the measurement sensitivity and signal-to-noise ratio (SNR) are enhanced by a factor of 18.

KDP-family crystals with large-diameter growth characteristics are ideal materials for obtaining high-energy deep-UV lasers. Based on the third-harmonic generation of 1064 nm laser and the 827 nm optical parametric oscillation pumped by 532 nm radiation, 248 nm deep-UV laser radiations were obtained via noncritical phase-matching (NCPM) sum-frequency generation in 89.6% and 98.8% DKDP crystals at 112.4 and 93.6 °C, respectively. The NCPM characteristics of the DKDP crystals were presented by tuning the crystal temperatures and incident angles, which was conducive to further exploiting the advantages of NCPM. This work presents a feasible high-energy 248 nm generation scheme to serve as the seed for the KrF excimer laser amplifier and pave the way for the energy improvement and applications of the deep-UV radiation by fully utilizing the large-diameter advantages of KDP-family crystals.

Aspherical optical elements have been widely used in modern optical systems, and the advanced measurement techniques are required to ensure the accurate characterization and quality control. A multi-plane phase retrieval method combined with varying-curvature illumination is presented, which greatly improves the convergence speed and reconstruction accuracy. The corresponding reconstruction algorithms and update methods are designed respectively for the reflective elements and the transmissive elements according to the optical path characteristics of different elements. This method was applied to the digital knife-edge instrument to achieve quantitative measurement. The PV deviations of the large-aperture transmissive and reflective elements from interferometer are both less than 30 nm. It provides a simple, low-cost and high-precision measurement tool for aspheric optical elements and has strong scalability.

By integrating χ(2) optical frequency conversion and χ(3) stimulated Raman scattering (SRS) technology, we demonstrated a new, to the best of our knowledge, deep-UV laser generation scheme near 200 nm in a non-cryogenic KD2PO4 (DKDP) crystal. Based on an Nd:YAG laser (1064 nm, ω1) and cascaded LiB3O5 and DKDP crystals, a 266 nm radiation was obtained firstly by the second- and fourth-harmonic generation (SHG and FHG) (ω4). The energy conversion efficiency from ω1 to ω4 was 24.8%. Meanwhile, the Stokes lights (ωR) were stimulated by the Nd:YAG laser in a KGd(WO4)2 crystal with two polarization-dependent Raman shifts of 768 cm-1 and 901 cm-1. Finally, 3.5 mJ, 216.3 nm, and 3.1 mJ, 217 nm deep-UV laser sources were obtained in a DKDP crystal by the sum-frequency generation (SFG) of ωR and ω4. The total conversion efficiency from 1064 nm infrared to ∼200 nm deep UV was ∼3%. This scheme, by systematically combining the χ(2) and χ(3) nonlinear effects, overcame the phase-matching limitation of traditional schemes to acquire high-energy 200 nm wave band deep UV via the fifth-harmonic generation (FiHG) in the DKDP crystal, which may provide a new way for the deep-UV laser generation with high energy and high-peak power.

The advent of spatiotemporal wave packets (STWPs), represented by spatiotemporal optical vortices (STOVs), has paved the way for the exploration in optics and photonics. To date, despite considerable efforts, a comprehensive and efficient practical means to characterizing wave packets with such complex structures is still lacking. In this study, we introduced a new method designed to achieve high-precision and high-throughput spatiotemporal wave packet measurements using a user-friendly set up. This method is based on a quadriwave lateral shearing interferometric wavefront sensor that utilizes wavelength division multiplexing, termed the "spatiotemporal wavefront sensor (STWFS)." Using this method, we have fabricated a compact prototype with 295 * 295 spatial pixels * 36 wavelength channels of 0.5 nm spectral resolution in a single frame. This STWFS enabled, for the first time, single-shot self-referenced spatiotemporal three-dimensional (3D) optical field characterizations of STOV pulses with transverse orbital angular momenta L of 1 and 2, and obtained the dynamic visualization of the focused propagation of STOV pulses. Furthermore, the STWFS provides a 1.87 nm (0.95