Laser Conditions Research Articles

Structure-Induced Energetic Coordination Compounds as Additives for Laser Initiation Primary Explosives.

Laser ignition of primary explosives presents more reliable alternative to traditional electrical initiation methods. However, the commercial initiator lead azide (LA) requires a high-power density laser to detonate, with the minimum laser initiation energy (Emin) of 2402 mJ. Currently, the laser-ignitable metal complex-based igniters still suffer from weak detonation capabilities and high Emin values. Here, the approach is first proposed to design laser ignition primary explosives within the high energy azide and tetrazole-based energetic coordination compounds (ECCs), [Co(N3)(2-bmttz)(H2O)]2 1 and [Co(N3)(2-bmttz)(MeOH)]2 2 as additives to LA. Material 1e with 4wt.% of 1 in LA, exhibits ultra-low laser initiation threshold (Emin = 1.6 mJ) and ultrafast corresponding time (Tmin = 0.2ms). Specially, compared to LA, the threshold of 1e is as low as 1/1500 of that of LA. Moreover, 30mg 1e successfully detonates RDX with a laser energy of 1.6 mJ. Theoretical calculations and experiment results reveal that 1 exhibits the superior additive effect compared to 2, attributed to its more enhanced ability to generate free radicals and higher photothermal conversion efficiency under laser conditions. This work represents a paradigm shift, with the potential to develop a laser-driven micro-detonator combining powerful detonation capabilities with exceptionally low laser initiation energy.

Advances in laser-based bremsstrahlung x-ray sources. I. Optimizing laser-accelerated electrons

In this work, we have performed a suite of kinetic simulations of relativistic laser–plasma interaction under settings relevant to recent and planned experiments on a variety of laser systems. The goal of the study is to illuminate the physics of laser–target coupling and to provide guidance for how to optimize these sources for applications. It is shown that the production of relativistic electrons is maximized when conditions of relativistic induced transparency (RIT) in dense plasmas can be achieved over a large interaction volume at the time of arrival of most intense part of the laser pulse. RIT is shown to enhance both the numbers of relativistic electrons and the energies of the electrons, leading to an increased x-ray dose. A variety of approaches to enhancing laser–target coupling are considered. These include optimizing the effects of low-density pre-plasma (arising either from finite laser pedestal or from the use of foam coatings) and of modifying the laser focusing geometry to reduce effects of filamentation and self-focusing. Evidence of a novel approach to achieving stable laser propagation over distances of tens of micrometers in a plasma gradient is also presented. These conditions coincide with plasma and laser conditions explored in recent experiments on the Omega EP laser system and compare favorably with an analytic criterion for stable laser propagation in relativistically underdense plasma obtained from a nonlinear Wentzel–Kramers–Brillouin analysis.

Influence of crystal orientation and incident plane on n-type 4H-SiC wafer slicing by using picosecond laser

Laser slicing has been considered as the most efficient technique for slicing SiC wafers with the advantages of small kerf width (loss) and crack, low roughness on cleaved surface, high quality and efficiency, etc. Here, laser slicing of n-type 4H-SiC was demonstrated by using a homemade 1064 nm picosecond laser combined with mechanical stretch stripping. The influence of laser processing along [11 2¯ 0] and [1 1¯ 00] crystal orientations on Si-face and C-face of n-type 4H-SiC, specifically on the internal laser ablation lines and cracks, the peeling tensile strength, and the surface roughness of the peeled surfaces was investigated. The semi-insulating 4H-SiC wafer laser slicing was conducted for comparison. Under the same laser conditions, laser slicing of semi-insulating 4H-SiC was easier than that of n-type. The laser modification quality along [1 1¯ 00] orientation was better than that along [11 2¯ 0] orientation for both the semi-insulating and n-type 4H-SiC and the reasons were explained. The results indicated that the optimal laser slicing scheme detailed laser scanning along [1 1¯ 00] orientation and incidence from the C-face. Finally, a 6-inch, 420.36 µm-thick n-type 4H-SiC wafer was successfully sliced.

Shear Bond Strength of Ceramic Brackets on Enamel Conditioned With CO2 Laser.

Objective This study evaluated the shear bond strength of ceramic brackets on enamel conditioned using three methods: CO2 laser, 37% phosphoric acid, and a combination of both, and analyzed the adhesive remnant index (ARI) to determine the amount of residual adhesive after bracket removal. Material and methods A total of 120 human premolars were stored in 0.2% thymol (Wt/vol) and divided into four groups (n=30/group): Group I was enamel conditioned with 37% phosphoric acid; Group II was irradiated with a CO2 laser at 0.5W power; Groups III and IV, 37% phosphoric acid; and CO2 laser wascombined at powers of 0.5W and 3W, respectively. Brackets were bonded using Transbond Plus CC resin. Samples were light-cured for 15 seconds and stored (37°C, 24 h). ARI assessment: The amount of adhesive remaining on the enamel surface was determined using a scale of 0 to 3. The analysis of shear bond strength and ARI was performed using the Kruskal-Wallis Test. Results Statistical analysis revealed significant differences between some groups. Group III, which combined acid etching and CO2 laser conditioning, showed lower bond strength than the control group, although not significantly. On the other hand, Group II (CO2laser only) showed the lowest bond strength and significant differences compared to the different groups, indicating that the exclusive use of laser is ineffective for conditioning. Significant differences were also observed between Groups III and IV, with Group IV exhibiting higher bond strength. However, the average value (GIII: 10.59±5.66 and GIV: 18.01±8.95 MPa) exceeded the recommended range (5.9 - 7.8 MPa). Regarding the ARI, Group II showed the lowest value, with significant differences compared to the other groups. Although Group IV had a higher ARI value than Group III, this difference was not statistically significant. Conclusions The combined use of phosphoric acid and CO2 laser provides adequate bond strength for ceramic brackets, with a lower amount of residual adhesive, which facilitates their removal and reduces the risk of damage to the enamel. Although laser irradiation alone does not provide sufficient bond strength, its use in combination with 37% phosphoric acid optimizes retention and minimizes the negative effects associated with conventional acid etching.

Three-dimensional reconstruction of laser-direct-drive inertial confinement fusion hot-spot plasma from x-ray diagnostics on the OMEGA laser facility (invited).

A deep-learning convolutional neural network (CNN) is used to infer, from x-ray images along multiple lines of sight, the low-mode shape of the hot-spot emission of deuterium-tritium (DT) laser-direct-drive cryogenic implosions on OMEGA. The motivation of this approach is to develop a physics-informed 3-D reconstruction technique that can be performed within minutes to facilitate the use of the results to inform changes to the initial target and laser conditions for the subsequent implosion. The CNN is trained on a 3D radiation-hydrodynamic simulation database to relate 2D x-ray images to 3D emissivity at stagnation. The CNN accounts for the lack of an absolute spatial reference and the different bands of photon energies in the x-ray images. While previous work [O. M. Mannion etal., Phys. Plasmas 28, 042701 (2021) and A. Lees etal., Phys. Rev. Lett. 127, 105001 (2021)] studied the effect of mode-1 asymmetries on implosion performance using nuclear diagnostics, this work focuses on the effect of mode 2 inferred from x-ray diagnostics on implosion performance. A current analysis of 19 DT cryogenic implosions indicates there is an upper limit of ∼20% reduction in the neutron yield caused by an ℓ = 2 amplitude for ℓ2/ℓ0 ≤ 0.32. These conclusions are supported by 2D simulations.

The efficacy and safety of pH-responsive and photothermal-sensitive multifunctional nanoparticles loaded with cryptotanshinone for the treatment of gastric cancer.

A multifunctional polydopamine/mesoporous silica nanoparticles loaded cryptotanshinone (PDA/MSN@CTS) was synthesized and subjected to investigating its physicochemical properties and anti-gastric cancer (GC) effects. Utilizing network pharmacology and molecular docking techniques, CTS was identified as our final research target. The structural morphology and physicochemical properties of PDA/MSN@CTS were examined. Near-infrared (NIR) laser was employed to evaluate the photothermal properties of the PDA/MSN@CTS, along with pH-responsive and NIR-triggered release assessments. In vitro experiments evaluated the impact of PDA/MSN@CTS on the malignant behavior of AGS gastric cells. A subcutaneous tumor model was further established to evaluate the in vivo safety of PDA/MSN@CTS. Furthermore, the in vivo photothermal efficacy of PDA/MSN@CTS, in addition to its combined effect with photothermal therapy (PTT), was investigated. Uniform and stable PDA/MSN@CTS had been successfully synthesized and demonstrated efficient release under tumor environment and NIR irradiation. Upon increasing NIR laser conditions, in vivo cytotoxicity, apoptosis rate, reactive oxygen species scavenging ability, and suppression of migration and invasion of AGS cells by PDA/MSN@CTS were significantly enhanced. In vivo assessments revealed excellent blood compatibility and biosafety of PDA/MSN@CTS, alongside robust tumor tissue targeting. Combining nanoparticles with PTT facilitated the anti-GC effects of PDA/MSN@CTS. Compared to free drugs, PDA/MSN@CTS exhibits higher selectivity towards cancer cells, demonstrating effective anticancer activity and biocompatibility both in vitro and in vivo. Furthermore, our nanomaterial possesses excellent photothermal properties, and under NIR conditions, PDA/MSN@CTS exhibits synergistic therapeutic effects.

Damage mechanism and bending properties degradation of aviation composite honeycomb sandwich structures under laser irradiation

Damage mechanism and bending properties degradation of aviation composite honeycomb sandwich structures are studied under different laser conditions in this paper. Firstly, the damage test of composite honeycomb sandwich structures is conducted. Temperature field and ablation process during laser irradiation are analyzed. Damage morphology and mechanism are verified. Secondly, the influence of laser damage on the bending properties of composite honeycomb panels is studied. Progressive damage process and failure mechanism of honeycomb structures during loading are explored by digital image correlation (DIC) and strain trend. The results show that the temperature at the center point of front surface reaches more than 2000 °C within 1 s under the laser irradiation, while the temperature of back surface exhibits hysteresis. The ablation hole is funnel-shaped and has severe delamination. In the heat affected zone (HAZ), resin matrix has been basically sublimated and oxidized, leaving only carbon fiber bundles and some residual carbon. The honeycomb core in this area has been completely carbonized and deformed. During bending process, the honeycomb core breaks firstly, and strain appears peak at both crack ends, leading the crack extend along both sides. The ultimate load of damaged specimen is 2.35kN, which has a 42.26 % drop compared to that of healthy specimen 4.07kN. Bending properties of specimen are significantly degraded by laser damage.

Thermo-Structural Coupled Finite Element Analysis of Repair Process for Steam Turbine Blade Using Laser-Directed Energy Deposition Method

This study presents a numerical additive manufacturing simulation aimed at simulating the shape recovery process of a steam turbine blade damaged by corrosion, using laser-directed energy deposition (LDED). The simulation integrates the finite element (FE) method with heat conduction and thermo-elastoplastic constitutive equations, incorporating phase transformation. The additive manufacturing process by LDED was modeled using the death-birth algorithm, wherein a deposition layer is defined as a virtual element. Its stiffness and thermal properties activated when the laser irradiation regions overlapped. In this study, the shape of the virtual element was determined based on the cross-sectional shape of the deposition layer manufactured under various laser conditions. To validate the numerical simulation results, additive manufacturing was conducted for one pass deposition in the width direction at the center of a cantilever-supported plate made of SUS304 steel, and the changes in displacement at the free edges with respect to the process time were compared. The obtained FE results are in good agreement with the experimental results. Finally, an FE simulation was performed for the shape recovery of a steam turbine blade thinned due to corrosion damage. The results revealed that the residual stress component becomes more compressive as the laser output decreases and scanning speed increases, which is advantageous for improving the fatigue strength of steam turbine blades.

Efficient laser-driven proton acceleration from a petawatt contrast-enhanced second harmonic mixed-glass laser system

Efficient laser-driven plasma acceleration of ion beams requires precision control of the target–plasma profile, which is crucial to optimize the laser energy transfer. Along the laser propagation direction, this can be achieved by tailoring the temporal structure of the laser pulse. We show for the first time that frequency-doubling of a short pulse (hundreds-femtosecond range) petawatt-class mixed-glass laser system, which results in temporal intensity contrast enhancement, enables surface and volumetric laser–energy coupling, and the acceleration of proton beams from few-nanometer-thick foil targets. Experimentally, maximum ion energies and laser-to-proton energy conversion efficiencies were found to be both maximized at optimum laser and target conditions manifested when the normalized target density nearly equalizes the normalized laser vector potential, which is in agreement with theory and simulations. These signatures are recognized as a unique indication of the interaction between ultra-intense laser pulses with high temporal intensity contrast and ultra-thin nanometer-scale targets. Transverse modulations of accelerated proton beams in the form of bubble- and ring-like structures measured in the thinnest targets provide additional evidence of volumetric laser-driven particle acceleration regimes and transitional features in ultra-thin foil targets specific to laser–plasma interactions characterized by a high temporal intensity contrast. These results open avenues in the generation of high contrast laser pulses from short-pulse-femtosecond petawatt mixed-glass laser systems and demonstrate the feasibility of this technique for applications requiring high laser intensity contrast with high efficiency.

Analysis method of point defects evolution in fused silica under multi-pulse nanosecond laser irradiation.

Although no optically visible damage is produced in the fused silica under laser irradiation below its laser-induced damage threshold (LIDT), defect proliferation may occur due to the evolution of its internal atomic structure. The escalation in defect content leads to heightened absorption, and resulting in the degradation of the optical performance of the optics. In recent decades, there have been a lot of experimental studies on laser-induced damage and laser conditioning, but there is still a great lack of in-depth understanding and theoretical analysis of the evolution process of point defects in fused silica. In this study, the emphasis is on the evolution of point defects and fatigue damage in fused silica under multi-pulse nanosecond laser irradiation. To address this, a point-defect evolution model is developed, and the coupled evolution law of temperature and defect during laser irradiation is derived by integrating it with a numerical model. The results demonstrate that the model effectively predicts the defect evolution of fused silica under laser irradiation and facilitates the prediction of fatigue damage. It is revealed that the rate of defect evolution in fused silica is more influenced by temperature than stress, and a temperature threshold can be used to judge the condition of damage occurrence. Furthermore, through an analysis of the effect of laser fluence on defect relaxation rate, a defect relaxation method employing variable laser fluence was proposed. This study provides a reliable theoretical analysis method for understanding the fatigue damage induced by multi-pulse laser irradiation in fused silica and offers a new perspective for the annealing treatment of point defects in fused silica.

Application of matrix-assisted laser desorption/ionization in the studies of phosphotungstic acid.

Phosphorotungstic acid (PTA) has many applications, especially in the field of catalysis, due to its structural properties. However, the structure of PTA is studied mainly using theoretical methods. Matrix-assisted laser desorption/ionization (MALDI) has the potential to be an effective method for the experimental study of heteropolyacids. Limitations of MALDI are the high molecular weight of the particles and the complex distribution of isotopic peak intensities. Both problems can be solved by automatically identifying observed signals by generating hypothetical molecular formulas and estimating their isotopic distributions. Phosphotungstic acid was studied under conditions of laser desorption/ionization in the absence and in the presence of the matrix. Three types of matrices were used: 2,5-dihydroxybenzoic acid in water, α-cyano-4-hydroxycinnamic acid in acetonitrile, and sinapic acid (SA) in tetrahydrofuran. Part of the peaks in the resulting mass spectra was identified using in-house developed software that implements the automated isotopic distribution brute force. The most informative mass spectra were obtained using SA as the matrix, which enabled the detection of particles containing PTA dimers for the first time. The compositions of particles incorporating PTA dimers were determined in an automated manner and can be written as [H3PW12O40]2·2H2O (m/z= 5791.2Da) and [H3PW12O40]2·4H2O (m/z = 5836.5Da). Other observed species included (WO3)n·PO3 -, HPO2·(WO3)n, and WO2·(WO3)n clusters, with the latter containing W in mixed oxidation states. The combined use of MALDI and an automated identification procedure provided valuable experimental data on the structure and fragmentation of phosphotungstic acid. To the best of our knowledge, this study was the first to report on particles containing phosphotungstic acid dimers.

Multishot laser damage of multilayer dielectric mirrors in the near-infrared subpicosecond regime

The laser damage resistance of dielectric components of high-power laser facilities to laser irradiation depends significantly on the irradiation sequence. In the short pulse (fs) regime, it is known that continuous irradiation of these components leads to a reduction in the damage threshold, reflecting a laser fatigue effect. Conversely, in the long pulse (ns) regime, progressive irradiation of these components leads to an increase in the damage threshold, reflecting a laser conditioning effect. In this article, we experimentally evaluate the competition between the effects of laser fatigue and laser conditioning for multilayer dielectric components irradiated in the subpicosecond pulse regime in the infrared (∼1µm) through different test sequences. For this purpose, we implemented an original test sequence derived from an S-on-1 type protocol, which consists of irradiating the component until damage. By repeating this sequence at different set points, it was possible to estimate the progressive reduction in damage threshold with the number of laser irradiations and to compare it with that observed during the fluence ramps. Particular attention was also paid to the precise knowledge of the test beam irradiating the component, as a dependence of the beam surface on the test set point was highlighted.

How to Crystallize Glass with a Femtosecond Laser

The crystallization of glass through conventional thermal annealing in a furnace is a well-understood process. However, crystallization by femtosecond (fs) laser brings another dimension to this process. The pulsed nature of the irradiation necessitates a reevaluation of the parameters for optimal crystallization and an understanding of the particularities of using fs laser. This includes adjusting the laser pulse energy, the repetition rate, and the writing speed to either initiate nucleation or achieve substantial crystal growth. Therefore, a key challenge of this work is to establish reliable calculations for understanding the link between the size of the crystallized region and an ongoing transition (e.g., solid-to-solid, liquid-to-solid), while accounting for the aforementioned laser parameters. In this context, and based on previous work, a temperature distribution (in space and time) is simulated to model the thermal treatment at any point in the glass. By setting the condition that the temperatures are between the glass transition and melting temperature, the simulated crystallized region size can be compared with experimental observations. For that purpose, knowledge of the beam width at the focal point and of the absorbed beam energy fraction are critical inputs that were extracted from experiments found in the literature. After that, the management of the crystallization process and the width of the crystallization line can be achieved according to pulse energy, e.g., crystallite size, and also the effect of the scanning speed can be understood. Among the main conclusions to highlight, we disclose the laser conditions that determine the extent of the crystallized area and deduce that it is never of interest to increase the pulse energy too much as opposed to the repetition rate for the uniform crystallized line.

Highly flexible liquid metal/photocurable polymer electrodes via direct laser patterning

A highly flexible electrode was fabricated using eutectic gallium-indium (eGaIn) liquid metal combined with an ultraviolet (UV)-curable polyurethane acrylate (PUA) polymer. The eGaIn liquid metal electrodes prepared by a negative-type direct patterning technique using a UV pulse laser can eliminate the need for complex photolithography masks. The optimal UV pulsed laser peak fluence was ∼1.43 J/cm2 to pattern and sinter the eGaIn/PUA composite electrode simultaneously. The laser-patterned eGaIn/PUA composite electrode under the optimal laser condition exhibited a remarkable electrical conductivity of 6.33 × 105 S/m with a patterning resolution of ∼40 μm. Moreover, the resistance of the electrode only deteriorated by 0.95% after 50,000 cycles of severe cyclic folding at a peak strain of 2.5% with a bending radius of 1 mm, demonstrating its exceptional flexibility and durability. These easily patterned eGaIn flexible electrodes via direct laser patterning techniques hold great promise for applications in wearable and flexible electronic devices that require extreme flexibility.

Linewidth Measurement of a Narrow-Linewidth Laser: Principles, Methods, and Systems.

Narrow-linewidth lasers mainly depend on the development of advanced laser linewidth measurement methods for related technological progress as key devices in satellite laser communications, precision measurements, ultra-high-speed optical communications, and other fields. This manuscript provides a theoretical analysis of linewidth characterization methods based on the beat frequency power spectrum and laser phase noise calculations, and elaborates on existing research of measurement technologies. In addition, to address the technical challenges of complex measurement systems that commonly rely on long optical fibers and significant phase noise jitter in the existing research, a short-delay self-heterodyne method based on coherent envelope spectrum demodulation was discussed in depth to reduce the phase jitter caused by 1/f noise. We assessed the performance parameters and testing conditions of different lasers, as well as the corresponding linewidth characterization methods, and analyzed the measurement accuracy and error sources of various methods.

Measure for optical robustness of directly bonded glass-to-glass joint using its interaction with damage induced by fs laser.

To produce more powerful compact ultrafast lasers, research aims at improving the quality of bonds between components inside the laser cavity. Increasing bond robustness under optical irradiation helps the bonds to survive the high energy pulses that these lasers are designed to produce. A measure for such robustness is reported here to support work toward improved bonding processes for such lasers. We produced bonds between pairs of optical grade fused silica glass cylinders using a wet direct bonding procedure. We evaluated these bonds using conventional microscopy, including scanning electron microscopy (SEM) and optical microscopy, without quantifiable results. The bond interface was not discernible through conventional SEM imaging, even after cross sectioning and polishing. The majority of the interface was also undetectable in optical micrographs, except for some limited areas of interfacial disturbance. To obtain quantifiable results for optical robustness, we used an 800nm femtosecond laser to produce filament-shaped damage from a focal spot moving across the interface. Microscopy of the damage showed its interaction with the interface, the presence of which caused a ≈0.130 to ≈0.230mm long interruption in the damage line. The exact value depended not only on laser power but also interface quality, and thereby quantified the optical robustness. The reported method proved more sensitive in detecting bonds of fused silica samples compared to other visualization techniques used. Our results suggest a nuanced understanding of bonded glass joints-mechanically sound, yet with limited optical robustness under specific laser conditions.

Matrix-assisted laser desorption/ionization matrix incorporation evaluation algorithm for improved peak coverage and signal-to-noise ratio in mass spectrometry imaging.

Despite decades of implementation, the selection of optimal sample preparation conditions for matrix-assisted laser desorption/ionization (MALDI) imaging is still ambiguous due to the lack of a universal and comprehensive evaluation methodology. Thus, numerous experiments with different matrix application conditions accompany a translation of the method to novel sample types and matrices. Mouse brain tissues were covered with 9-aminoacridine through sublimation, followed by recrystallization in vapors of 5% (v/v) methanol solution in water. The samples were analyzed by MALDI time-of-flight mass spectrometry, and the efficiency of lipid and small-molecule ionization was evaluated with different metrics. We first investigate the dependency of matrix density and recrystallization conditions on the thickness of an analyte-empty matrix layer to roughly evaluate the laser shot number required to obtain an intense signal with minimal noise. Then, we introduce metrics for the analysis of small imaging datasets (small sample regions) of model samples based on median quantity of peaks in spectra (medQP) and weighted median signal-to-noise ratio (wmSNR). The evaluation of small regions and taking median values for metrics help overcome the sample heterogeneity and allow for the simultaneous comparison of different acquisition parameters. Here, we propose a methodology based on gradual laser ablation of small regions of sample and further implementation of weighted signal-to-noise ratio to assess various matrix application conditions. The proposed approach helps reduce the number of test samples required to determine optimal sample preparation conditions and improve the overall quality of images.

Photobiomodulation improves acute restraint stress-induced visceral hyperalgesia in rats

The purpose of this study is to explore the potential application of photobiomodulation to irritable bowel syndrome. We established the following experimental groups: the Non-Stress + Sham group, which consisted of rats that were not restrained and were only subjected to sham irradiation; the Stress + Sham group, which underwent 1 hour of restraint stress followed by sham irradiation; and the Stress + Laser group, which was subjected to restraint stress and percutaneous laser irradiation bilaterally on the L6 dorsal root ganglia for 5 minutes each. The experiment was conducted twice, with three and two laser conditions examined. Following laser irradiation, a barostat catheter was inserted into the rat’s colon. After a 30-minute acclimatization period, the catheter was inflated to a pressure of 60 mmHg, and the number of abdominal muscle contractions was measured over a 5-minute period. The results showed that photobiomodulation significantly suppressed the number of abdominal muscle contractions at average powers of 460, 70, and 18 mW. However, no significant suppression was observed at average powers of 1 W and 3.5 mW. This study suggests that photobiomodulation can alleviate visceral hyperalgesia induced by restraint stress, indicating its potential applicability to irritable bowel syndrome.

Laser Patterning of Porous Support Membranes to Enhance the Effective Surface Area of Thin-Film Composite-Facilitated Transport Membranes for CO2 Separation.

Although thin-film composite membranes have achieved great success in CO2 separation, further improvements in the CO2 permeance are required to reduce the size and cost of the CO2 separation process. Herein, we report the fabrication of composite membranes with high CO2 permeability using a laser-patterned porous membrane as the support membrane. High-aspect-ratio micropatterns with well-defined micropores on their surface were carved on microporous polymer supports by a direct laser writing process using a short-pulsed laser. By using a Galvano scanner and optimizing the laser conditions and target materials, in-plane micropatterns, such as microhole arrays, microline grating, microlattices, and out-of-plane hierarchical micropatterns, were created on porous membranes. An aqueous suspension of hydrogel microparticles doped with an amine-based mobile carrier was sprayed onto the patterned surface to form a defect-free thin separation layer. The surface area of the separation layer on the patterned support is up to 80% larger than that of flat pristine membranes, resulting in a 52% higher CO2 permeance (1106 GPU) with a CO2/N2 selectivity of 172. The laser-patterned porous membranes allow the development of inexpensive and high-performance functional membranes not only for CO2 separation but also for other applications, such as water treatment, cell culture, micro-TAS, and membrane reactors.

Crescent-shaped spatial distribution: radiation properties concerning beam waist from the cross collision of a tightly focused laser pulse and a relativistic electron

The radiation properties of the cross collision between a single electron and an intense laser pulse are researched by numerical simulation methods. Under the condition of tightly-focused laser, the electron trajectories, spatiotemporal distribution and spectrum are compared with that under non-tightly focused lasers. The results show that the torsion effect on the electron during the oscillation process is more notable after the tightly focused laser interacts with electron. The radiation it generates is asymmetric in space, and its time distribution is nearly unimodal and can be regarded as a single attosecond pulse. In frequency domain, the spectrum appears to be a supercontinuum. With the increase of beam waist radius, the symmetry of the spatial distribution enhances and time distribution also exhibits a three-peak structure that is symmetrical about the main peak. Furthermore, the spectrum changes from a supercontinuum to a multimodal distribution. The analysis turns out that tightly focused laser is more realistic compared to non-tightly focused laser or even plane wave, which benefits the design of high-quality x-rays in practical application.