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Laser shock forming (LSF) is a novel plastic forming process which utilizes a laser-induced shock wave to deform metal sheet to 3D configurations. Quantitative evaluation of the deformation in LSF is of great importance to understand the forming mechanism and achieve the high precision. In this paper, an analytical model was proposed to predict the deformation of a circular plate in laser shock bulging process. Models showed that the deformation is related to material parameters such as the impedance, density, yield strength of the metal target, geometric parameters such as the plate thickness and die radius, and processing parameters such as the energy, radius and pulse duration of the laser beam. The deformation profiles and the maximum deformation height calculated by the analytical model agree with those of experiment, which validate the rationality of the constructed models. The maximum deformation height increases with an increase of laser energy and decreases with increasing plate thickness. [ABSTRACT FROM AUTHOR]

In Laser decal transfer process, the materials are printed in micron-sized dots without changing its phase from thin film coated substrate (donor substrate). The pulsed laser irradiates the donor substrate opposite to the coated side and transfers the material in the same phase to another substrate kept very close to the donor substrate. The process has shown its potential for printing microsensors without any changes in physical and functional properties during the printing process for the electronics components. Generally, ZnO-based patterned structure is still challenging for the existing manufacturing techniques without hampering its functionality in the sensing application. In this work, an attempt has been made to print ZnO structure in solid phase using maskless µ-3D printing using a long-pulsed CO2 laser. A two-dimensional numerical model in COMSOL Multiphysics is developed to estimate the temperature induced by the laser irradiation on the sacrificial layer, and energy conservation is applied to estimate the particle's velocity. A deformed mesh geometry is used to predict the ablation depth of the sacrificial layer after the laser irradiation. The deformed geometry shows the ablated area in the sacrificial layer, and the temperature induces a different time frame. The ZnO ceramic film is coated on the sacrificial layer followed by the laser µ-3D printing of ZnO on silicon wafer using CO2 laser at three laser fluence, i.e., 530 mJ/cm2, 1030 mJ/cm2, and 1530 mJ/cm2 with 90% pulse overlap. The ejection of ZnO from substrate is visualized using a high-speed camera by shadowgraphy techniques. The ejection mode is defined based on the deviation of the particle from the laser beam direction. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is increasingly viable for the high-volume production of complex parts due to material and time savings, weight reduction, design optimization, and the development of new materials. Laser metal deposition (LMD), a specific AM process, offers high build rates and larger deposition volumes, making it cost-effective for industries such as aerospace and defense, which benefit from increased productivity and the ability to repair large components. Martensitic stainless steels are valued for their mechanical properties in these sectors, despite the challenges of maintaining these properties during LMD deposition. The purpose of this study was to evaluate the deposition parameters for laser cladding using LMD with AISI 431 martensitic stainless steel powder and to analyze the morphological aspects. Microstructural evolution was assessed using optical and electron microscopy, with samples produced by varying laser power (800, 1000, 1400, 1600 W) and scanning speed (9, 14, 16 mm/s). The results showed dilution values between 10 and 27% for power values of 1400 and 1600 W for all laser beam velocities tested. Microstructural characterization revealed martensite and ferrite phases in the deposits. Increasing the scanning speed resulted in higher dilution and wettability and decreased the height/width ratio of the deposits. The laser deposition parameters also affected the solidification parameters (G/R) and the cooling rate (G × R), which are critical for understanding the resulting microstructure and hardness of the deposits. This study highlights the importance of considering geometric and microstructural aspects in LMD for AISI 431 steel to ensure high productivity and optimal performance and demonstrates the potential of the LMD process for the deposition of martensitic stainless steel. [ABSTRACT FROM AUTHOR]

TianQin is expected to deploy three spacecraft in Earth orbit at the altitude of about 1 × 108 m to form an equilateral triangular constellation with arm lengths of about 1.7 × 108 m. It is aimed at detecting gravitational waves in the frequency range from 0.1 mHz to 1 Hz by means of high sensitive laser ranging interferometry with pathlength measurement noise below 1 pm/Hz1/2. The long-range propagation of beam in the intersatellite laser ranging interferometry between the three spacecraft results in a non-negligible time delay of 0.58 s. Therefore, there is an angular difference between the optimal outgoing and incoming laser beam of laser ranging interferometry on each spacecraft, which is denoted as the point-ahead angle. Due to the relative motion between the three spacecraft, the point-ahead angle of TianQin constellation is approximately 22.96 μrad with a dynamic variation range of ±24.71 nrad. Point-ahead-angle mechanism is a fine steering mirror used for point-ahead angle compensation to diminish the beam pointing error, thus to maintain the intersatellite laser link as well as to diminish the tilt-to-length coupling noise, which are vital to the gravitational wave detection. Both the static and dynamic point-ahead angle compensation strategies can be used in TianQin and the selection of the two is based on minimizing the total point-ahead-angle-related tilt-to-length coupling noise. In this paper, a criteria for selection of the two strategies are proposed by establishing a model of point-ahead-angle-related tilt-to-length coupling noise as well as a corresponding evaluation function for calculation and comparison. The results indicate that the dynamic compensation strategy is the optimal choice only when the first-order tilt-to-length coupling coefficient of point-ahead-angle mechanism is less than 6.4 × 10−9 m/rad, otherwise the static compensation strategy should be used. The proposed criteria, as well as the model and the requirement for point-ahead-angle mechanism, can serve as a common theoretical basis in laser ranging interferometry applications. • Criteria for selection of point-ahead angle compensation strategies. • Minimize tilt-to-length coupling noise in intersatellite laser interferometry. • Quantitative comparison of tilt-to-length noise in different compensation strategies. • Static compensation strategy is more appropriate in TianQin according to the criteria. [ABSTRACT FROM AUTHOR]

We report an application of a pulsed ultraviolet (UV) laser (λ = 355 nm) in producing translucent Si solar cells. This process efficiently generates a densely packed microhole array on a fully fabricated Si P‐N junction solar cell in just a few minutes. Herein, prototype cells with a nominal microhole diameter of 23 μm with a spacing between 60 and 300 μm are fabricated. High‐resolution electron‐beam microscopy reveals that the UV laser beam introduces amorphized silicon oxide (SiOx) in proximity to the patterned microholes via localized heating in air. Quantitative photovoltaic (PV) analysis shows a decline in the open‐circuit voltage (Voc) and the fill factor (FF) of the cells with the increase in the microhole density, likely due to the P‐N junction damage during the laser beam irradiation. Despite the reduction in Voc and FF, the solar cells retain a short‐circuit current density (Jsc) above 90% without post‐processing. The inherent microhole geometry associated with the laser beam profile allows multiple light scattering within the confined microhole structure, enhancing the translucency of the cells. While further development is required for optimization, these findings support the potential use of UV laser beams for fast and scalable production of translucent solar cells. [ABSTRACT FROM AUTHOR]

Quantum cascade lasers (QCLs) in the mid-infrared (MIR) hold significant potential for widespread applications in both military and civilian contexts. However, the utility of present single-chip QCLs is hampered by issues such as low output power and subpar beam quality. This study addresses these limitations by employing spectral beam combining (SBC) based on a diffraction grating, with an aim to enhance both power and beam quality of MIR QCLs. Coaxial power synthesis of three single-chip QCLs (around 4.75 μm) is achieved experimentally, importantly, the beam quality did not decrease after combining, essentially maintaining the same quality as before combining. It is proposed that there are four main factors affecting the combining efficiency, namely operating optical power (or driving current) of the chips, individual differences in QCL chips, diffraction grating, and reflectivity of feedback mirror, and their effects on the combining efficiency are discussed separately. This study confirms that SBC is an effective way to obtain high-power and high-beam quality MIR QCL sources, and lays a research foundation for more beam spectral combining. [ABSTRACT FROM AUTHOR]

The treatment of keloids, particularly in high‐tension areas, is challenging due to their extension beyond the original wound boundaries and high recurrence rates, thereby rendering traditional treatments ineffective. In this study, we investigated the effectiveness of a novel single‐stage treatment approach that combined acellular dermal matrix (ADM) with keloid‐specific epidermal skin grafting. To further prevent recurrence after neo‐skin formation, the treatment was followed by fractionated laser and radiation therapy (LCR). Seven patients with high‐tension keloids, including one with keloids at two locations, were treated and followed‐up for an average of 15.9 months. The patients showed significant improvements in wound healing and skin appearance, with a marked reduction in the Patient and Observer Scar Assessment Scale (POSAS) (scores from 91.1 ± 5.6 to 23.8 ± 6.1 (p < 0.001)). This approach effectively minimizes tension, reduces the likelihood of keloid recurrence, and serves as a viable alternative to conventional methods that often involve challenges related to donor‐site acquisition. No recurrence was observed during the follow‐up period, indicating a promising innovation in the management of extensive keloids and offering improved healing and esthetic outcomes, particularly in high‐tension areas. [ABSTRACT FROM AUTHOR]

Multiscale parameter optimization for laser peen forming (LPF) on 6005A-T6 aluminum alloy plates was conducted through a combination of simulation and experimentation. By obtaining the optimal parameter, this study aims to explore the constrained deformation and forming laws of the integral stiffened plates. Detailed descriptions were provided regarding the dynamic response process and transient behavior of aluminum alloy plates under ultrahigh strain rates, along with an in-depth analysis of the stress evolution. The results reveal that laser beam diameter and laser beam energy can achieve large range forming, while the number of tracks facilitates the precise deformation adjustment. During the 12-track LPF process, there is an overall upward trend in deformation values accompanied by a dynamic increase in the bend curvature. After static relaxation, the deformation value recovers to 55.2% of the final bending curvature. The chord direction scanning of stiffened plates exhibits a larger bending curvature, indicating its greater forming capacity for large-sized single unfolding direction formation; whereas, the unfolding direction scanning of stiffened plates excels in achieving efficient integrated two-way forming. [ABSTRACT FROM AUTHOR]

Research into the efficacy of photobiomodulation therapy (PBMT) in reducing inflammation has been ongoing for years, but standards for irradiation methodology still need to be developed. This study aimed to test whether PBMT stimulates in vitro human peripheral blood mononuclear cells (PBMCs) to synthesize pro-inflammatory cytokines, including chemokines. PBMCs were irradiated with laser radiation at two wavelengths simultaneously (λ = 808 nm in continuous emission and λ = 905 nm in pulsed emission). The laser radiation energy was dosed in one dose as a whole (5 J, 15 J, 20 J) or in a fractionated way (5 J + 15 J and 15 J + 5 J) with a frequency of 500, 1,500 and 2,000 Hz. The surface power densities were 177, 214 and 230 mW/cm2, respectively. A pro-inflammatory effect was observed at both the transcript and protein levels for IL-1β after PBMT at the energy doses 5 J and 20 J (ƒ=500 Hz) and only at the transcript level after application of PBMT at energy doses of 20 J (ƒ= 1,500; ƒ=2,000 Hz) and 5 + 15 J (ƒ=500 Hz). An increase in CCL2 and CCL3 mRNA expression was observed after PBMT at 5 + 15 J (ƒ=1,500 Hz) and 15 + 5 J (ƒ=2,000 Hz) and CCL3 concentration after application of an energy dose of 15 J (frequency of 500 Hz). Even though PBMT can induce mRNA synthesis and stimulate PBMCs to produce selected pro-inflammatory cytokines and chemokines, it is necessary to elucidate the impact of the simultaneous emission of two wavelengths on the inflammatory response mechanisms. [ABSTRACT FROM AUTHOR]

Lateral flow assay (LFA) is a handful diagnostic technology that can identify severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other common respiratory viruses in one strip, which can be tested at the point-of-care without the need for equipment or skilled personnel outside the laboratory. Although its simplicity and practicality make it an appealing solution, it remains a grand challenge to substantially enhance the colorimetric LFA sensitivity. In this work, we present a straightforward approach to enhance the sensitivity of LFA by imposing the flow constraints in nitrocellulose (NC) membranes via a number of vertical femtosecond laser micromachined microchannels which is important for prolonged specific binding interactions. Porous NC membrane surfaces were structured with different widths and densities µ-channels employing a second harmonic of the Yb:KGW femtosecond laser and sample XYZ translation over a microscope objective-focused laser beam. The influence of the microchannel parameters on the vertical wicking speed was evaluated from the video recordings. The obtained results indicated that µ-channel length, width, and density in NC membranes controllably increased the immunological reaction time between the analyte and the labeled antibody by 950%. Image analysis of the colorimetric indicators confirmed that the flow rate delaying strategy enhanced the signal sensitives by 40% compared with pristine NC LFA. [ABSTRACT FROM AUTHOR]

In addressing the issues of laser defocusing, laser beam interference, and low melting efficiency prevalent in current gear laser cladding path planning, a method for gear laser cladding path planning is formulated based on area segmentation and trajectory refinement. Firstly, the tooth surface model is reconstructed using three times NURBS surfaces. Subsequently, the tooth failure region is extracted through point cloud data alignment and Boolean operations, and the laser scanning region is preliminarily delineated using a graphical convolutional neural network. This is further refined by employing an ant colony algorithm. Secondly, by employing a geometrically constrained mathematical model of the gear, the compensation distance for laser focusing and the feasible domain range of the laser beam are determined to effectuate the trajectory refinement for the gear's laser cladding. Finally, completing the laser scanning area division and trajectory correction to perform the laser cladding gear repair experiment, the experiment relies on the HLC40 laser powder feeding additive manufacturing workstation, adopting the YLR-4000IPG laser for cladding operation. The experimental results demonstrate the absence of focus offset and laser beam interference during the cladding process. Moreover, the total travel distance of the planned path was reduced by 9–12%, the cladding time was reduced by 8–16%, and the morphological quality of the cladding layer was improved by 39–46%. [ABSTRACT FROM AUTHOR]

We study the formation of surface relief structures in azo-polymers generated via two-photon induced photoisomerization using a femtosecond near-infrared optical vortex laser beam. These structures exhibit exotic flower-like shapes with petals along the azimuthal direction, and they are formed from spatial mode instability, which is associated with third-order nonlinear effects in the azo-polymer. This process is a unique and exotic interaction between light and matter, which may be applied to the development of advanced optical data storage technologies. Here, an additional degree of freedom is offered by the number of formed petals, which themselves are a function of the topological charge of the optical vortex beam. [ABSTRACT FROM AUTHOR]

We investigate the dynamics of electrons initially counter-propagating to an ultra-fast ultra-intense near-infrared laser pulse using a model for radiation reaction based on the classical Landau–Lifshitz–Hartemann equation. The electrons, with initial energies of 1 GeV, interact with laser fields of up to 10 23 W/ cm 2 . The radiation reaction effects slow down the electrons and significantly alter their trajectories, leading to distinctive Thomson scattering spectra and radiation patterns. It is proposed to use such spectra, which include contributions from harmonic and Doppler-shifted radiation, as a tool to measure laser intensity at focus. We discuss the feasibility of this approach for state-of-the-art and near-future laser technologies. We propose using Thomson scattering to measure the impact of radiation reaction on electron dynamics, thereby providing experimental scenarios for validating our model. This work aims to contribute to the understanding of electron behavior in ultra-intense laser fields and the role of radiation reaction in such extreme conditions. The specific properties of Thomson scattering associated with radiation reaction, shown to be dominant at the intensities of interest here, are highlighted and proposed as a diagnostic tool, both for this phenomenon itself and for laser characterization in a non-intrusive way. [ABSTRACT FROM AUTHOR]

Spectrum-narrowed and -locked broad-area diode lasers operating at 780 nm are essential for rubidium laser development. With the help of Littrow-type transmission gratings, we demonstrated a simple scheme with a narrow linewidth and the diode laser's center wavelength locked without thermal drift, in contrast to volume Bragg gratings. By carefully collimating the diode laser beam, we realized a linewidth narrower than 0.17 nm and a side-mode suppression ratio over 20 dB. Furthermore, broad-spectrum tuning at 9 nm was demonstrated by grating angle tuning. This method could easily be adapted to other wavelength diode lasers. [ABSTRACT FROM AUTHOR]

(1) Background: The significant progress observed over the last two decades in coherent beam combining (CBC) technology has mainly focused on its applications in high-energy physics and laser weapons. This work provides insight into the basic principles of CBC and the search for an alternative, namely optical angular momentum (OAM) generation using CBC. (2) Methods: A semi-analytical model based on the paraxial wave equation was explored, generating OAM-CBC beams by manipulating the tilts and phases of the CBC (T&P-CBC) of hexagonal architecture. (3) Results: The specially arranged T&P-CBC shows typical properties of OAM, such as annular profiles for the zero diffraction order and 1st-order replicas in the far field and correlation coefficients of 1% between different OAM-CBC fields. (4) Conclusions: The differences between classical OAM beams and OAM-CBC are substantial due to hexagonal lattice properties. Moreover, applications in free space optical communications are feasible as T&P CBC fulfills the main conditions and requirements for OAM generation. [ABSTRACT FROM AUTHOR]

This study investigates the synthesis, characterization, and antimicrobial properties of hydrogels synthesized through the UV-pulsed laser photopolymerization of a polymer–photoinitiator–chlorpromazine mixture. Chlorpromazine was used for its known enhanced antimicrobial properties when exposed to UV laser radiation. The hydrogel was formed from a mixture containing 0.05% Irgacure 2959, 10% gelatin methacryloyl, and various concentrations of chlorpromazine (1, 2, and 4 mg/mL). Laser-induced fluorescence spectroscopy was employed to monitor the photoinduced changes of chlorpromazine and Irgacure 2959 during hydrogel formation, providing insight into the photodegradation dynamics. FTIR spectroscopy confirmed the incorporation of irradiated chlorpromazine within the hydrogel matrix, while the release profiles of chlorpromazine showed sustained release only in hydrogels containing 1 mg/mL of CPZ. The hydrogel showed significant antimicrobial activity against MRSA bacteria when compared to that of penicillin. These findings highlight the potential of CPZ loaded during the photopolymerization process into hydrogels as effective antimicrobial agents with sustained release properties, making them suitable for combating resistant bacterial strains. [ABSTRACT FROM AUTHOR]

Micro-stereolithography (μ SL) is an advanced additive manufacturing technique that enables the fabrication of highly precise microstructures with fine feature resolution. One of the primary challenges in μ SL is achieving and maintaining precise focus throughout the fabrication process. For the successful application of μ SL, it is essential to maintain the sample surface within a focal depth of several microns. Despite the growing interest in auto-focus devices, limited attention has been directed towards auto-focus systems in image-based auto-focus microscope systems for precision μ SL. To address this challenge, we propose an image-based auto-focus microscope system incorporating visual servo control. In the optical design, a transflective beam splitter is employed, allowing the laser beam to pass through for fabrication while reflecting the focused beam on the sample surface to the microscope and camera. Utilizing captured spot images and the Foucault knife-edge test, a deep learning-based laser spot image processing algorithm is developed to determine the focus position based on spot size and the number of spot pixels on both sides. Experimental results demonstrate that the proposed auto-focus system effectively determines the relative position of the focal point using the laser spot image and achieves auto-focusing through visual servo control. [ABSTRACT FROM AUTHOR]

In this paper, we propose a simple method to generate the uniform illumination using a pyramid prism for Plane Array Laser Imaging Detection and Ranging (PA-LiDAR). The principle of the pyramid prism shaping the Gaussian beam to form a uniform beam was analyzed theoretically. By changing the parameters of the pyramid prism and laser beam, the profile distribution of the output beam can be easily adjusted. Based on the operation mode and illumination requirements of PA-LiDAR, we have developed a set of LiDAR prototypes using a pyramid prism and carried out experimental research on these prototypes. The simulation and experimental results demonstrated that this method can achieve a uniform illumination beam with excellent propagation properties for meeting the technical requirements of PA-LiDAR. This method of uniform illumination has the advantages of being simple, flexible, easily adjustable and convenient to operate. [ABSTRACT FROM AUTHOR]

In the field of numerical control machining, tool alignment technology is a key link to ensure machining accuracy and quality. Tool alignment refers to determining the correct position of the tool relative to the workpiece, and its accuracy directly affects the precision of part machining. With the development of precision machining technology, the research and application of cutting technology are increasingly valued. Tool alignment methods are mainly divided into two categories: contact and non-contact. The contact type tool alignment method relies on direct contact between the tool and the workpiece or tool alignment instrument to measure the position. Among them, the trial cutting method is a traditional contact type tool alignment method that determines the tool position through actual cutting, which is intuitive but inefficient. The contact type tool presetter uses specialized equipment to improve the accuracy and efficiency of tool presetting through contact measurement. The non-contact tool alignment method does not rely on physical contact, while the image method uses image recognition technology to determine the tool position, making it suitable for high-precision applications. The laser diffraction method and the laser direct method use laser technology for non-contact measurement. The laser diffraction method determines the position of the tool by analyzing the diffraction mode of the laser beam, while the laser direct method directly measures the distance between the laser and the tool. This article mainly introduces the classification of tool alignment, commonly used knife alignment methods and common tool alignment devices, as well as the development status of international tool alignment instrument products. [ABSTRACT FROM AUTHOR]

Featured Application: The presented study proposes technology for increasing stealth and preventing the unmasking of objects, including orbital ones, by forming a complex two-period surface microstructure using femtosecond laser processing. Currently, the technology of imparting the necessary reflective properties to a surface is becoming increasingly important. Darkening the surface and matting it helps to diffuse the reflected beam and prevent glare. The surface's reflective properties are determined by its microstructure. Modern pico- and femtosecond lasers make it possible to obtain surfaces with high precision and create various LIPSS (laser-induced periodic surface structure) types. In this article, we describe the process of formation of a complex two-periodic microstructure on the surface of AISI 321 stainless steel under the influence of radiation from femtosecond lasers and describe the process of scattering of a light beam by the resulting surface. Modeling shows that the presence of an additional transparent coating on a flat surface does not improve its scattering properties and does not eliminate glare. In the event that a complex two-periodic structure is formed on the reflective surface and the coating surface, the nature of the reflection has a clearly defined scattered character, regardless of the angle of incidence of the light beam. This study shows the feasibility and effectiveness of forming a two-periodic structure in order to give it stealth characteristics and reduce visibility. [ABSTRACT FROM AUTHOR]

Poor vacuum stability limits the application of many matrices in matrix‐assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) that requires long‐term measurement duration in high vacuum. In this study, a new approach using conjugate polymer anchor to protect unstable matrix from volatilizing in MALDI source based on ion bond is provided. Unlike strong covalent bonds which often introduce unnecessary groups, the weaker ion bonds are more conducive to breaking under laser radiation while effectively preventing matrix volatilization in a vacuum environment. The results confirm that conjugate polymer anchor will neither introduce additional ion peaks nor affect signal intensity, yet maintains comparable quantification properties. Vacuum stability of three kinds of typical matrices is enhanced using polymer anchors, and the in situ MALDI MS imaging of mouse brain and liver cancer is improved significantly. [ABSTRACT FROM AUTHOR]

Preclinical studies on pathological pain rely on the von Frey test to examine changes in mechanical thresholds and the acetone spray test to determine alterations in cold sensitivity in rodents. These tests are typically conducted on rodent hindpaws, where animals with pathological pain show reliable nocifensive responses to von Frey filaments and acetone drops applied to the hindpaws. Pathological pain in orofacial regions is also an important clinical problem and has been investigated with rodents. However, performing the von Frey and acetone spray tests in the orofacial region has been challenging, largely due to the high mobility of the head of testing animals. To solve this problem, we implemented a sheltering tube method to assess orofacial nociception in mice. In experiments, mice were sheltered in elevated tubes, where they were well accommodated because the tubes provided safe shelters for mice. Examiners could reliably apply mechanical stimuli with von Frey filament, cold stimuli with acetone spray, and light stimuli with a laser beam to the orofacial regions. We validated this method in Nav1.8-ChR2 mice treated with oxaliplatin that induced peripheral neuropathy. Using the von Frey test, orofacial response frequencies and nociceptive response scores were significantly increased in Nav1.8-ChR2 mice treated with oxaliplatin. In the acetone spray test, the duration of orofacial responses was significantly prolonged in oxaliplatin-treated mice. The response frequencies to laser light stimulation were significantly increased in Nav1.8-ChR2 mice treated with oxaliplatin. Our sheltering tube method allows us to reliably perform the von Frey, acetone spray, and optogenetic tests in orofacial regions to investigate orofacial pain. [ABSTRACT FROM AUTHOR]

When reflected from an interface, a laser beam generally drifts and tilts away from the path predicted by ray optics, an intriguing consequence of its finite transverse extent. For twisted light, such beam shifts manifest even more dramatically: upon reflection, a field containing a high-order optical vortex is expected to experience not only geometrical shifts, but an additional splitting of its high-order vortex into a constellation of unit-charge vortices, a phenomenon known as topological aberration. In this article, we report on the experimental observation of the topological aberration effect, verified through the deformation of vortex constellations upon reflection. We develop a general theoretical framework to study topological aberrations in terms of the elementary symmetric polynomials of the coordinates of a vortex constellation, a mathematical abstraction which we prove to be the physical quantity of practical interest. In this article, the authors devised an experiment to measure the subtle changes suffered by light fields containing optical singularities in their interactions with matter, showing that material information can be retrieved from such measurements. [ABSTRACT FROM AUTHOR]

In the present communication, binary (ZnO:Ga 2 O 3 - 1:1 (ZGO), ZnO:Ga 2 O 3 - 2:1 (GaZn))/ternary (EZG (Eu 2 O 3 : ZnO: Ga 2 O 3 (1:1:1)), MZG (MgO: ZnO: Ga 2 O 3 (1:1:1)) NCs are synthesized by P i p e r b e t l e leaves extract as a reducing agent followed by calcination at 600 °C for 3 h. The Bragg reflections confirms the formation of single phase cubic symmetry with F d 3 m space group in ZGO NCs whereas reflections related individual metal oxides are observed in the GaZn, EZG and MZG NCs. The irregular size and shaped nanoparticles are observed in all the synthesized NCs. The tuned band gap was found to be in the range of 3.08 to 3.11 eV. The optical nonlinearity of the specimens was analyzed using the open aperture Z-scan technique. The material demonstrated reverse saturable absorption attributed to a two-photon absorption (2PA) process. The non linear absorption coefficient follows the order MZG > GaZn > ZGO > EZG. However, the optical limiting threshold follows the order ZGO > GaZn > MZG > EZG NCs with increase in energy band gap. These outcomes distinctly indicate the superior potential of GaZn binary NCs for optical limiting applications. This characteristic is advantageous for shielding sensors and the human eye, safeguarding them against the detrimental effects of intense green laser radiation. [ABSTRACT FROM AUTHOR]

Porous alumina structures were developed by indirect Powder Bed Fusion with Laser Beam (PBF-LB), employing a novel feedstock (composite granules) based on alumina (Al 2 O 3), bio-renewable polyamide 612 (PA612), and micron-sized graphite (MG) using a commercial PBF-LB machine that operates with a low-power visible light diode laser. Regular and slightly rounded composite granules were prepared via the thermally induced phase separation (TIPS) process in dimethyl sulfoxide (DMSO) using 0.05 vol% of PA612, 40/60 vol% of Al 2 O 3 /PA612 and 6.25 wt% of MG, and then characterized via density measurements, Hausner's ratio, SEM-EDS, particle size distribution, Raman spectroscopy, DSC, and TGA. Experimental conditions to be used in the PBF-LB process were determined in order to obtain high-quality green porous structures with a controlled geometry. After the heating treatments, sintered components with good structural integrity, a high open porosity associated with interconnected pores in the struts, and a ceramic matrix with microsized-equiaxial grains were obtained. The evaluation of the mechanical properties was performed by diametral compression testing. In order to improve these properties, a vacuum infiltration process involving a low-concentration alumina-ethanol suspension was used on pre-sintered discs. As a consequence of the infiltration process, the discs showed improved mechanical properties after sintering without the porosity having been significantly affected. [ABSTRACT FROM AUTHOR]

We present a new selective Metamaterial Perfect Absorber (MPA) consisting of zinc oxide embedded silver (Ag@ZnO), designed for applications in infrared stealth technology. The numerical simulation included a wide frequency range from 1 to 1000 THz and shows that the design MPA structure presented two absorption peaks at the desired wavelengths of 1.7 µm and 6.5 µm. The absorptivity of both peaks reached approximately 93.1% and 93.5%. The first peak at 1.7 µm decreases the scattering of IR laser beams from the surface of the MPA structure and also lowers the infrared tracks that could direct laser-guided devices to its specific target. On the other hand, the second peak reduces the surface heat wave. The suggested MPA (Ag@ZnO) structure is activated by a plane wave using a full wave vector and a broad frequency domain solution. In the framework of computer simulation technology (CST) Microwave Studio, uses both Finite-Difference-Time-Domain (FDTD) and Finite-Element-Method (FEM) techniques to predict the optical behavior of the proposed MPA structure. Both peaks achieved a high value of absorptivity due to the simultaneous excitation of the electric and magnetic dipole at resonance wavelength. [ABSTRACT FROM AUTHOR]

The preliminary results of experimental modeling of the impact process on a coal substance by short-pulse laser radiation are presented. During the experiments, extremely high temperatures and pressures were reached. Based on the analysis of the modified products of the target substance, coal melting was identified, followed by its cooling with subsequent solidification with the formation of glass-like carbon. The synthesis products may be of interest as novel carbon materials formed at ultrahigh pressures and temperatures, such as high-pressure carbon polymers and hollow fullerene-like structures. The results of experimental modeling can be used for comparison with naturally occurring materials in order to elucidate the mechanisms of the formation of natural high-pressure carbon substances from a non-graphite precursor. [ABSTRACT FROM AUTHOR]

The light pressure of an evanescent electromagnetic wave formed by total internal reflection near the flat interface of a dielectric and a liquid on a dielectric spherical nanoparticle located in a liquid medium is considered. Phase portraits of a two-dimensional system of equations that is equivalent to the equation of nanoparticle transportation under the influence of the force gradient of the light pressure of the evanescent field taking into account the medium resistance force are plotted. Various phase portraits can be realized both without equilibrium points and with one equilibrium point (stable focus, stable node or saddle) on the phase plane, depending on the parameters of the laser radiation and the material of the nanoparticle suspended in the water. [ABSTRACT FROM AUTHOR]

The correct conditions for measuring the luminescence intensities in fi laments formed by the action of femtosecond laser pulses were found for lithium fluoride crystals. The determined conditions ensured that the measured intensities were proportional to the concentrations of luminescent color centers created in the crystals by the laser radiation and allowed conclusions to be drawn about the processes occurring in the filaments. Near-cluster color centers were found, indicating the presence of nanosized clusters in all areas of the fi laments. [ABSTRACT FROM AUTHOR]

In this study, a ring light point cloud calibration technique based on collimated laser beams is developed, aiming to reduce errors caused by the position and attitude changes of traditional ring light measurement devices. This article details the generation mechanism of the ring beam and the principle of deep hole measurement. It introduces the collimated beam as a reference, building on traditional ring light measurement devices, to achieve the synchronous acquisition of the ring beam and collimated spot images by an industrial camera. The Steger algorithm is employed to accurately extract the coordinates of the point cloud contours of both the ring beam and the collimated spot. By analyzing the shape and position changes of the collimated spot contour, the spatial position and attitude of the measuring device are precisely determined. This technique is applied to the 3D reconstruction of the inner surface of deep holes, ensuring the accurate restoration of the spatial positional attitude of the ring beam by incorporating the spatial positional attitude parameters of the measuring device to precisely calibrate the cross-sectional point cloud coordinates. Experimental results with ring gauges and deep hole workpieces demonstrate that this technique effectively reduces the percentage of point cloud data outside the tolerance range, and improves the accuracy of the 3D reconstruction model by 6.287%, thereby verifying the accuracy and practicality of this technique. [ABSTRACT FROM AUTHOR]

The effect of a laser beam on the development of cracks in an AL-6061 aluminum plate at various aspect ratios of 1:1, 1:1.5, and 1:2 was investigated in this study. The investigation adopted two clamping types: Clamped-Free-Clamped-Free and Simply-Free-Simply-Free, and supported the plate with a 5 mm crack length. The study aimed to investigate the duration it takes for cracks to propagate when subjected to the impact dynamic load after being exposed to 500 watts of laser power. Compared to the plate with an aspect ratio of 1:2 and the CFCF clamping type that was not subjected to the laser beam, the numerical results showed a 36% increase while increasing by 37% in the experimental results. Furthermore, compared to the plate that was not exposed to the laser beam and had the same boundary conditions, the clamping SFSF type of aluminum plate under dynamic load showed an increase in the number of beats that are required for crack growth of 29% according to experimental results and 28% according to numerical results. The results presented show that clamping conditions have a significant impact on the growth of cracks in the plate. It was found that a crack requires more beats to grow in a crack with an aspect ratio of 1:1 than in a crack with an aspect ratio of 1:1.5, which is larger than the aspect ratio of 1:2. Furthermore, the plate with the CFCF clamping type requires fewer pulses for the crack to grow than the plate with the SFSF clamping type. The heat of a laser beam altered the microstructure of an aluminum plate, generating residual stresses and increasing its surface hardness, thereby enhancing its crack resistance and failure resistance properties. The SEM images showed how the laser beam affected the microstructure of the sample's surface, enhancing its resistance to crack growth compared with the aluminum plate's surface, which was not exposed to the laser beam, and appears smoother. [ABSTRACT FROM AUTHOR]

This study investigates the microstructural effects of process parameters on Ti6Al4V alloy produced via powder bed fusion (PBF) using laser beam melting (LB/M) technology. The research focuses on how variations in laser power, exposure velocity, and hatching distance influence the final material's porosity, microhardness, and microstructure. To better understand the relationships between process parameters, energy density, and porosity, a simple mathematical model was developed. The microstructure of the alloy was analyzed in the YZ plane using a confocal microscope. The study identified optimal parameters—302.5 W laser power, 990 mm/s exposure velocity, and 0.14 mm hatching distance—yielding the lowest porosity index of 0.005%. The material's average hardness was measured at 434 ± 18 HV0.5. These findings offer valuable insights for optimizing printing parameters to produce high-quality Ti6Al4V components using PBF-LB/M technology, shedding light on the critical relationship between process parameters and the resulting microstructure. [ABSTRACT FROM AUTHOR]

In this study, crack-free TiC/Ti composites with TiC content ranging from 0 to 15 wt.% were successfully fabricated using Direct Energy Deposition with a dual-feeder system that concomitantly delivered different amounts of both constituents into a high-power laser beam. The samples were investigated to evaluate the morphologies and distribution behavior of TiC. The microhardness values of the samples obtained under optimal processing conditions increased from 192 ± 5.3 HV0.2 (pure Ti) to 300 ± 14.2 HV0.2 (Ti + wt.% 15 TiC). Also, TiC has a significant impact on the Ti matrix, increasing the strength of TMCs up to 725 ± 5.4 MPa, while the elongation drastically decreased to 0.62 ± 0.04%. The wear rate is not proportionally affected by the rise content of TiC reinforcement; the hypoeutectic region of TMCs exhibited a wear rate of 2.45 mm3/N·m (Ti + wt.% 3 TiC) and a friction coefficient of 0.48 compared to the ones from the hypereutectic region, which measured a wear rate of 3.02 mm3/N·m (Ti + wt.% 15 TiC) and a friction coefficient of 0.63. The improved values of mechanical properties in the case of TMCs as compared to pure Ti are provided due to the solid solution strengthening of carbon and the fine grain strengthening. This work outlines a method for changing TiC morphologies to improve the hardness and tensile strength of TMCs fabricated starting from micro-scale powder. [ABSTRACT FROM AUTHOR]

Automating forest machines to optimize the forest value chain requires the ability to map the surroundings of the machine and to conduct accurate measurements of nearby trees. In the near-to-medium term, integrating a forest harvester with a mobile laser scanner system may have multiple applications, including real-time assistance of the harvester operator using laser-scanner-derived tree measurements and the collection of vast amounts of training data for large-scale airborne laser scanning-based surveys at the individual tree level. In this work, we present a comprehensive processing flow for a mobile laser scanning (MLS) system mounted on a forest harvester starting from the localization of the harvester under the forest canopy followed by accurate and automatic estimation of tree attributes, such as diameter at breast height (DBH) and stem curve. To evaluate our processing flow, we recorded and processed MLS data from a commercial thinning operation on three test strips with a total driven length ranging from 270 to 447 m in a managed Finnish spruce forest stand containing a total of 658 reference trees within a distance of 15 m from the harvester trajectory. Localization reference was obtained by a robotic total station, while reference tree attributes were derived using a high-quality handheld laser scanning system. As some applications of harvester-based MLS require real-time capabilities while others do not, we investigated the positioning accuracy both for real-time localization of the harvester and after the optimization of the full trajectory. In the real-time positioning mode, the absolute localization error was on average 2.44 m, while the corresponding error after the full optimization was 0.21 m. Applying our automatic stem diameter estimation algorithm for the constructed point clouds, we measured DBH and stem curve with a root-mean-square error (RMSE) of 3.2 cm and 3.6 cm, respectively, while detecting approximately 90% of the reference trees with DBH > 20 cm that were located within 15 m from the harvester trajectory. To achieve these results, we demonstrated a distance-adjusted bias correction method mitigating diameter estimation errors caused by the high beam divergence of the laser scanner used. [ABSTRACT FROM AUTHOR]

The Pohang Accelerator Laboratory X‐ray Free‐Electron Laser (PAL‐XFEL) operates hard X‐ray and soft X‐ray beamlines for conducting scientific experiments providing intense ultrashort X‐ray pulses based on the self‐amplified spontaneous emission (SASE) process. The X‐ray free‐electron laser is characterized by strong pulse‐to‐pulse fluctuations resulting from the SASE process. Therefore, online photon diagnostics are very important for rigorous measurements. The concept of photo‐absorption and emission using solid materials is seldom considered in soft X‐ray beamline diagnostics. Instead, gas monitoring detectors, which utilize the photo‐ionization of noble gas, are employed for monitoring the beam intensity. To track the beam position at the soft X‐ray beamline in addition to those intensity monitors, an X‐ray ionization beam position monitor (XIBPM) has been developed and characterized at the soft X‐ray beamline of PAL‐XFEL. The XIBPM utilizes ionization of either the residual gas in an ultra‐high‐vacuum environment or injected krypton gas, along with a microchannel plate with phosphor. The XIBPM was tested separately for monitoring horizontal and vertical beam positions, confirming the feasibility of tracking relative changes in beam position both on average and down to single‐shot measurements. This paper presents the basic structure and test results of the newly developed non‐invasive XIBPM. [ABSTRACT FROM AUTHOR]

The aim of this article is to determine the microhardness, the tribological behavior, and the microstructure of a Ti-6Al-4 V alloy nitrided with a pulsed Nd-YAG (neodymium-doped yttrium aluminum garnet) laser under nitrogen gas flow. The Ti alloy's surface was irradiated and melted at different laser scanning speeds. X-ray diffraction revealed three phases: α-Ti, TiN, and TiN0.3. Optical and scanning electron microscopy results revealed dendritic microstructure in both laser-melted and nitrided zones with TiN dendrites concentrated near the alloy's surface. Furthermore, surface's wear examination using pin-on-disk tribometer revealed that the wear morphology depends on the thickness of the TiN nitrided layer (2–8 μm); thus, the enhanced wear resistance is observed in the case of the sample with thicker TiN layer obtained under a laser beam speed of 2.5 mm/s. [ABSTRACT FROM AUTHOR]

Full-penetration laser welding processes are necessarily associated with significant changes of the geometrical properties of the keyhole at the beginning of the process when the keyhole expands all the way through the workpiece and finally pierces the bottom of the sheet. The impact that this transition has on the absorptance was investigated by means of X-ray imaging to determine the geometry of the keyhole and subsequent raytracing to calculate the distribution of the absorbed irradiance. The results show a significant drop of the overall absorptance when the bottom of the capillary opens through the rear side of the workpiece which in practice is noticed by an unstable behavior of the keyhole. Since the drop of the absorptance is less pronounced for smaller diameters of the keyhole, one may recommend the application of laser beams with small diameters at least during the initial phase until the keyhole is fully developed and reliably reaches through the bottom surface of the welded sheet. [ABSTRACT FROM AUTHOR]

Keyhole laser-based processes have been adopted widely due to the high-quality welds and cuts that they produce and the accurately controlled dimensions of the end part. Fast-running simulation tools are required in order to estimate the dependence of process outputs, efficiency, and stability on the process variables. This work presents a fast-running simulation tool for keyhole laser-based processes with inert or no assisting gas that takes into account the effect of laser beam defocusing and the alteration of the effective reflectivity of the material due to the keyhole cavity. The model is built upgrading a successful model for the thermal phenomena based on finite differences and the enthalpy method. The presented model is compared to experimental results for the laser cutting process with both CO 2 and fiber laser sources and inert assisting gas. The model accurately predicts cutting depth and kerf, heat-affected zone width, and the dependence of the cutting depth on the position of the focal plane. The model manages to achieve reduced computational time enabling its utilization in process digital twins. [ABSTRACT FROM AUTHOR]

This research aims to detect and analyze critical internal and surface defects in metal components manufactured by powder bed fusion of metals using a laser beam (PBF‐LB/M). The aim is to assess their impact on the fatigue behavior. Therefore, a combination of methods, including image processing of micro‐computed tomography (μCT) scans, fatigue testing, and machine learning, was applied. A workflow was established to contribute to the nondestructive assessment of component quality and mechanical properties. Additionally, this study illustrates the application of machine learning to address a classification problem, specifically the categorization of pores into gas pores and lack of fusion pores. Although it was shown that internal defects exhibited a reduced impact on fatigue behavior compared with surface defects, it was noted that surface defects exert a higher influence on fatigue behavior. A machine learning algorithm was developed to predict the fatigue life using surface defect features as input parameters. Highlights: Established workflow for extracting surface and internal features.Developed pore classification ML algorithm with 92.4% accuracy.Effectively developed ML algorithm for predicting fatigue life. [ABSTRACT FROM AUTHOR]

The purpose of the study was to investigate the effectiveness of minimally invasive methods, such as laser-induced interstitial thermotherapy (LITT) and its combination with percutaneous ethanol ablation (PEA), in treating toxic thyroid adenomas. To determine the multiplicity of the LITT procedure and parameters of laser radiation to achieve a stable positive therapeutic effect. Materials and methods. Between 2020 and 2024, 24 patients with Plummer's disease who did not receive previous thyrostatic therapy before the LITT session were treated and were divided into 2 groups. Patients of the first group with a predominantly parenchymal structure of the node received LITT monotherapy (16 patients), patients of the second group with an existing cystic component received percutaneous ethanol sclerotherapy followed by LITT (8 patients). Patients underwent ultrasound and hormonal follow-up after laser ablation at 2, 4, and 6 months. Study endpoints: percent nodal volume reduction compared to pretreatment volume (VRR), thyroid-stimulating hormone (TSH), free thyroxine, free triiodthyronine, TSH-receptor antibodies. Results. All patients had a positive result of treatment. The average nodal volume reduction ratio (VRR) for patients in the first group was 88.3 ± 7.9 % (min — 71.5, max — 95.4), and for patients in the second group — 72 % (min — 59.5, max — 85.4). The percentage of patients in whom the euthyroid status was recorded after the first session ranged from 100 % for nodes of smaller volume (up to 4 cm³ ) to 63 % for nodes of maximum volume (up to 13 cm³). After the completed treatment (the maximum number of LITT sessions — 4), all patients had a stable euthyroid status. The effective specific energy for solid nodules is ≈ 900 J/ml, for mixed cystic-parenchymal nodules the specific energy is lower and ≈ 790 J/ml (for the volume of the nodule after PEA). Complications: one case of bleeding was recorded, and a moderate pain syndrome: 6 points on the Visual Analog scale. Conclusions. Laser thermal ablation of toxic thyroid adenomas under ultrasound guidance offers an additional safe and effective minimally invasive treatment option. Reduction of solid thyroid nodules is effective over time if the specific energy exceeds 900 J/ml (for the primary nodule volume). The reduction of mixed cystic-parenchymal nodules is effective under the condition of the effectiveness of ethanol, the specific energy for such nodules is less than ≈ 790 J/ml (for the volume of the nodule after PEA). The total energy for the course of treatment should not be less than the calculated (Е∑ ≈ Espec × Vnode). Clinical outcomes are significantly more favorable in small toxic adenomas than in large nodes. [ABSTRACT FROM AUTHOR]

The most frequently used method for measuring surface roughness is profilographometry. However, with complex and non-homogeneous surfaces, this method may be subject to large errors because of its contact nature and limitations related to the geometry of the measuring head. In this study, the surface topography was examined on polypropylene injection moldings produced using an injection mold with a complex molding cavity surface. The moldings were modified using a Nd:YAG laser, and the obtained structures were examined using two measurement methods, i.e. contact (profilographometry) and optical (3D digital microscopy). Researchers performed a statistical analysis to determine the differences between the measurement results obtained for the two methods. Additionally, the impact of the laser parameters on the modified surface was determined. The obtained results showed significant differences between the values of measurements made using different methods, especially in the case of surfaces that were modified by the laser beam to the greatest extent (laser A parameters). In all cases where a statistically significant difference was found between the measurement results, the mechanical method showed lower roughness values than the optical method, and the average difference between these results was 15%. [ABSTRACT FROM AUTHOR]

Additive manufacturing methods give the opportunity to produce interesting, new structures with a more complicated topology than would be possible using traditional methods. Using the selective laser sintering method, a disk with a high roughness and porous structure was produced. Studies of material surface were performed on microscopic devices. An in vitro experiment was performed on the manufactured disk using mice fibroblastic cells. The designed shape enabled the growth of the cell culture in the disc pores and ensured impermeability of the disc base. On the basis of the average viability of 79%, which is close to reference well (80%), preliminary results confirmed that the manufactured structures create sufficiently comfortable conditions for the cell cultures without the need to design their internal topography. Controlling the production parameters of SLS printing allows obtaining the structures characterized by spatial and surface porosity without designing inner geometry of the structure. Polyamide 2200 (PA2200) powder with a laser beam, offers new possibilities for producing surfaces used in the tissue engineering, bioreactors, and microfluidics devices. [ABSTRACT FROM AUTHOR]

Highly intense bunches of protons and ions with energies of several MeV/u can be generated with ultra-short laser pulses focused on solid targets. In the most common interaction regime, target normal sheath acceleration, the spectra of these particles are spread over a wide range following a Maxwellian distribution. We report on the design and testing of a magnetic chicane for the selection of protons within a limited energy window. This consisted of two successive, anti-parallel dipole fields generated by cost-effective permanent C-magnets with customized configuration and longitudinal positions. The chicane was implemented into the target vessel of a petawatt laser facility with constraints on the direction of the incoming laser beam and guidance of the outgoing particles through a vacuum port. The separation of protons and carbon ions within distinct energy intervals was demonstrated and compared to a ray tracing code. Measurements with radiochromic film stacks indicated the selection of protons within [2.4, 6.9] MeV, [5.0, 8.4] MeV, or ≥6.9 MeV depending on the lateral dispersion. A narrow peak at 4.8 MeV was observed with a time-of-flight detector. [ABSTRACT FROM AUTHOR]

In this paper, promising but simple schemes are investigated to enhance the micro-bunching of relativistic electron beams for coherent harmonic generation (CHG) by using phase merging effects. In contrast to the standard CHG scheme, two specially designed dispersion sections (DSs) are adopted with the DS-modulator–DS configuration. The phase space of the e beam is appropriately coupled in the first DS, and the electrons within one seed wavelength can merge to the same phase with a matched second DS. Micro-bunching of the e beam can thus be enhanced by a large margin with much higher-harmonic components. Taking e beams from laser wakefield accelerators (LWFAs) as an example, start-to-end simulations are performed to show the effectiveness and robustness of the proposed schemes with several configurations. The beam current can be optimized to several tens to hundreds of kiloamperes, and the radiation power reaches hundreds of megawatts in the extreme ultraviolet regime within a 3.5 m-long beamline. The proposed schemes offer new opportunities for future compact free-electron lasers driven by LWFAs and provides prospects for truly compact and widely applicable systems. [ABSTRACT FROM AUTHOR]

TEM00-mode operation is a requirement in many laser-based applications due to the small divergence and high-power density of the emitted laser beam. A solar laser scheme was designed and numerically studied with the goal of increasing the solar-to-laser power conversion efficiency in the TEM00-mode operation. The collection and primary concentration of sunlight was performed via twelve sets of folding mirrors and Fresnel lenses, toward a laser head composed of a fused silica torus volume and seven Ce:Nd:YAG rods, in a side-pump configuration. With this scheme, TEM00-mode laser power totaling 212.39 W could potentially be produced from seven beams, with six of them being 32.60 W each and with M x 2 = 1.00,   M y 2 = 1.01 quality factors. Notably, 35.40 W/m2 collection efficiency and, most importantly, 3.73% solar-to-laser power conversion efficiency were numerically achieved. The latter efficiency value represents a 1.81-time improvement over the experimental record, established with a prototype that had a single Ce:Nd:YAG rod in an end-side pump configuration. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study of the dynamic characteristics of the process of laser fragmentation/laser-induced fluorescence (LF/LIF) of trinitrotoluene traces on a paper surface under synchronized double-pulse laser irradiation. An Nd:YAG-laser (266 nm) was used for the fragmentation of TNT molecules, while fluorescence excitation of their NO fragments was performed using a KrF laser with a generation line of 247.867 nm in the region of the location of the bandhead of the P12 branch of the γ(0, 2) absorption band of the NO molecule. It was shown that the dissociation process of TNT traces has an inertial character and continues after the cessation of the fragmenting laser pulse. It was found that with the delay values between the fragmenting and probing laser pulses in the region of 200 ns, the efficiency of the LF/LIF method can be increased by 12 times. This paper presents the results of an experimental evaluation of the efficiency of two-pulse LF/LIF compared to single-pulse laser exposure, where the fragmentation of TNT molecules and excitation of their NO fragments were simultaneously performed by KrF laser pulses. The possibility of multiple increases in the efficiency of two-pulse LF/LIF with an increase in the energy density of the fragmenting laser radiation was shown. The obtained results are important in terms of increasing the sensitivity and/or range of the LF/LIF method for remote detection of traces of nitrocompounds. [ABSTRACT FROM AUTHOR]

The objective of this study, which is divided into two parts, is twofold: to address long-standing challenges in the sensing of atmospheric turbulence-induced wavefront aberrations under strong scintillation conditions via a comparative analysis of several basic scintillation-resistant wavefront sensing (SR-WFS) architectures and iterative phase retrieval (IPR) techniques (Part I, this paper), and to develop a framework for the potential integration of SR-WFS techniques into practical closed-loop non-astronomical atmospheric adaptive optics (AO) systems (Part II). In this paper, we consider basic SR-WFS mathematical models and phase retrieval algorithms, tradeoffs in sensor design and phase retrieval technique implementation, and methodologies for WFS parameter optimization and performance assessment. The analysis is based on wave-optics numerical simulations imitating realistic turbulence-induced phase aberrations and intensity scintillations, as well as optical field propagation inside the SR-WFSs. Several potential issues important for the practical implementation of SR-WFS and IPR techniques, such as the requirements for phase retrieval computational grid resolution, tolerance with respect to optical element misalignments, and the impact of camera noise and input light non-monochromaticity, are also considered. The results demonstrate that major wavefront sensing requirements desirable for AO operation under strong intensity scintillations can potentially be achieved by transitioning to novel SR-WFS architectures, based on iterative phase retrieval techniques. [ABSTRACT FROM AUTHOR]

The object of this work is the effect of a laser beam surface treatment on the micro-mechanical and tribological properties of biomedical Co-28Cr-6Mo alloy manufactured by different methods (casting-forging or Laser Powder Bed Fusion (LPBF)). The wrought and LPBF alloys were superficially melted by the laser beam of 400 W power (fiber laser «TruFiber 400» (TRUMPF) of 1064 nm wavelength) under a scanning velocity of 5 mm·s-1. The research was fulfilled using an optical (GX71 OLYMPUS) and electron scanning microscopy (JSM-7000F JEOL), X-ray diffraction (X'Pert PRO, PANalytical, Cu-Kα radiation), nanoindentation (“G200 Nano Indenter”, Agilent Technologies) and tribological testing (a “Ball (Al2O3)-on-Plate” sliding in a simulated body fluid). It was found that laser treatment resulted in a modified (remelted) layer with a depth of 500-550 μm having mainly the εCo phase (HCP) structure formed by dispersed dendrites. The dendrite cross-section size varied from 5-12 μm (in the primary arms) to 1.5-6.0 μm in the secondary arms; these values are much lower than the average grain size in the wrought unmodified alloy (44 µm). Laser treatment increased the hardness and yield strength of the wrought alloy by 23 % (to 5.21 GPa), and decreased the volume wear by 25 %. In contrast, laser surface melting hardly changed the micromechanical and tribological properties of the LPBF alloy since its structure was not refined relatively the as-printed (unmodified) state. However, the melting-induced densification (porosity elimination) of the modified layer was observed in the LPBF alloy thus indicating the positive effect of laser modification on the structure of the LPBD-manufactured components. [ABSTRACT FROM AUTHOR]

The PH 13-8 Mo family of steels belong to the martensitic precipitation hardening stainless steels (MPHSSs) category, which exhibits a good combination of mechanical properties and corrosion resistance. Additive manufacturing (AM) offers advantages, including reduced material waste and the capability to produce complex, near-net-shape parts. Consequently, the application of AM techniques to the PH 13-8 Mo family is being increasingly explored across various industries. This review paper presents the existing literature on the topic and provides an overview. The review starts by presenting information about the PH 13-8 Mo family, including microstructure, chemical compositions, heat treatments, and mechanical properties. Afterwards, the work focuses on presenting the microstructure and resulting properties of PH 13-8 Mo family processed by three different additive manufacturing processes: Powder Bed Fusion using a Laser Beam (PBF-LB), Directed Energy Deposition using an Electric Arc (DED-Arc), and Directed Energy Deposition using a Laser Beam (DED-LB), both in their as-built condition and following post-processing heat treatments. The review concludes with a summary and outlook that highlights existing knowledge gaps and underscores the need for further research to tailor the microstructural evolution and enhance the properties. The findings indicate that AM of the PH 13-8 Mo family has the potential for industrial applications, yet further studies are necessary to optimize its performance. [ABSTRACT FROM AUTHOR]