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It is highly desired to be able to readily and robustly fabricate carbon patterns on cellulose paper (CellP) with complicated 3D structures, which would allow for cost-effectively developing a variety of resilient and stable paper-based sensors. Upon a pretreatment of CellP with NH4H2PO4, herein, we present a one-step direct laser writing carbonization (DLWc) method capable of in situ creating electrically conductive carbon features on the NH4H2PO4 treated CellP. With assistance of infrared spectroscopy, thermogravimetry and differential scanning calorimetry, the role of NH4H2PO4 in the pyrolysis/carbonization of cellulose paper to enhance the resultant carbon yield was investigated. The loadings of NH4H2PO4 in CellP and the laser processing conditions were studied for their effects on morphology/structure and electrical property of the carbon line features created by DLWc on the NH4H2PO4 treated CellP. Upon taking advantage of the unique mechanical characteristics of corrugated paper sheets, we further utilized the one-step DLWc process to fabricate disposable, lightweight, and low-cost paper-based sensors and demonstrated their use for sensing force, displacement, wind flow and finger-tapping position recognition. The one-step DLWc of CellP will lead a way towards large-scale, environmental-benign and cost-effective production of multifunctional paper-based sensors. [ABSTRACT FROM AUTHOR]

The safety and efficacy of laser hair removal have been well established through many clinical studies and through clinical use over the past 25 years. A laser hair removal device that protects the epidermis by utilizing cryogen spray cooling (CSC) is widely used internationally. In darker skin types, post-inflammatory hyperpigmentation (PIH) can occur after laser hair removal. In particular, laser hair removal with CSC is known to cause crescent-shaped or ring-shaped PIH. In this experiment, we report a visualization of this PIH mechanism. The laser used in this experiment is a 755-nm-long-pulsed alexandrite laser. Graph paper was treated with this laser to assess for thermal damage. We investigated changes in thermal damage due to differences in laser spot size, fluence output, and laser beam angle in relation to the graph paper. When using a spot size of 18 mm, we observed that higher fluences caused crescent-shaped thermal damage on the margins of the treated graph paper. It was also confirmed that when the hand piece is not held perpendicular to the skin, the laser-treated area is expanded and the CSC range is narrowed. These factors caused the area of thermal damage to widen. This widening causes ring-shaped thermal injury, leading to PIH. We treated graph paper using a hair removal laser with CSC to investigate the mechanism of crescent or ring-shaped thermal damage. Laser treatment on graph paper is effective as a test for defects in the CSC device. Factors that cause inadequate cooling, which leads to PIH, are large spot size, high fluence, not holding the laser hand piece perpendicular to the skin, and malfunctioning of CSC device. [ABSTRACT FROM AUTHOR]

Laser cleaning of historic paper infected by foxing is far more effective at 157 nm than in other laser wavelengths because at 157 nm localized photo-dissociation of organic matter is taking place at low laser energy. In addition spatial control over exposed areas with resolution better than 100 nm is possible at this wavelength. In order to optimize the methods of laser cleaning of historic paper, foxing ablation experiments at 157 nm indicate that infected paper areas can be removed with controllable spatial resolution in the nanometer scale. In addition foxing samples were investigated by scanning electron microscopy and X-ray analysis. It was found that biological activity was present on paper areas containing traces of iron. [ABSTRACT FROM AUTHOR]

We report on the successful use of a KrF excimer laser as a highly promising tool to investigate the accelerated ageing of wood Kraft papers used as insulating components in high-voltage power transformers. The effects of varying both the laser repetition rate (5 to 180 Hz) and the laser energy density (0.02 to 0.11 J?cm-2) on the degradation of wood Kraft paper in air were systematically investigated. During the laser irradiation experiments, the temperature of the paper samples was real-time measured by means of an IR camera. It is shown that the ageing temperature of the paper can be controlled very precisely by simply adjusting the laser parameters. Indeed, levelling-off temperatures in the 25-320 °C range can be reached after only 3 s of laser exposure, by either varying the repetition rate at a fixed energy density or changing the laser fluence at a given pulse rate. By performing both scanning electron microscopy (SEM) observations and measurements of the degree of polymerization (DPv) of the laser irradiated paper samples, we were able to demonstrate that the laser irradiation induces a very rapid degradation of the paper samples (typical laser exposure times are around 35 s to be compared with ~10 days for standard dynamic heating based ageing tests). Both the DPv of the irradiated paper samples and the average width of the corresponding cellulose fibers as measured from SEM micrographs, are shown to reduce by about 50% following their laser heating at ~320 °C for 35 s of exposure time. It is pointed out that the observed laser-induced degradation is predominantly a photothermal process. Finally, by using gas chromatography/mass spectrometry (GC/MS), we were able to show that low molecular weight compounds such as acetaldehyde, methyl formate, acetone, and methanol are produced not only by the laser ageing process but also in real on-field transformers that underwent a severe short-circuit. [ABSTRACT FROM AUTHOR]

The main goal of this study was to determine the reproducibility of the reading of wrist trauma case radiographs using three different media: laser film, a picture archiving and communication systems (PACS) workstation, and paper with an optimized layout. The study was conducted retrospectively in 200 consecutive patients consulting at the emergency department for wrist trauma and who underwent wrist X-ray investigation using a computed radiography system. There were 82 men and 118 women. The mean age was 48.3 years (16-95 years). Our institutional review board does not require patient approval or informed consent for retrospective review of case records. The readings were made by two independent readers who analyzed the 200 patient radiographs consecutively in one session for each type of media: paper, laser film, and on a PACS dual-screen workstation. The inter-reader agreements were substantial or almost perfect, with kappa values of 0.83 (0.76-0.90) for the PACS, 0.83 (0.76-0.90) for film, and 0.80 (0.72-0.87) for paper. The inter-technique agreement was almost perfect in all cases. There is a high interobserver agreement between PACS, laser film, and paper readings for wrist trauma cases. With a layout of one radiograph on each sheet, paper could replace laser films to communicate the results of wrist radiographs in trauma cases for outpatients. [ABSTRACT FROM AUTHOR]

Laser cleaning is an attractive and advanced technique of cleaning cultural heritage materials. However, in the case of paper-based substrates, it may lead to surface discoloration and long-term destabilisation of the cellulosic component. The origin of discoloration during pulsed laser removal (Nd:YAG laser, 532 and 1064 nm) of carbonaceous soiling was studied using UV resonance Raman spectroscopy and X-ray photoelectron spectroscopy. It was concluded that macromolecular conjugated systems are the most probable cause of discoloration, formed as a consequence of thermolytic reactions. With chemiluminometry, we analysed the processes following irradiation. Using photo-ageing and thermally accelerated ageing, it was indicated that, even at fluences lower than the ablation threshold of cellulose, long-term destabilisation of the material should be taken into account. By using much lower laser shot repetition rates than usual, i.e. 1 s-1, we can allow the substrate to cool between consecutive laser shots, thus minimising the adverse effects of laser treatment. Acoustic monitoring was shown to be an affordable possibility for on-line process control. The amplitude of shock waves was shown not to be wavelength dependent (532 or 1064 nm); however, the parameter can be used to monitor the progress of cleaning. [ABSTRACT FROM AUTHOR]

The oral cavity is a unique and complex environment, where hard and soft tissues exist in close proximity, within bacteria-laden saliva. All oral tissues are receptive to laser treatment, but the biophysics governing laser-tissue interaction demands a knowledge of all factors involved in delivery of this modality; through this knowledge, correct and appropriate treatment can be delivered in a predictable manner. [ABSTRACT FROM AUTHOR]

The word laser conjures in the mind's eye many aspects of what might be described as 'modern' life. The words 'powerful', 'precise' and 'innovative' complement our conception of the world in terms of technology, whereas patients often associate the words 'magical' and 'lightening quick' with the use of lasers in medical practice. The purpose of this series of articles is to explore the history and development of lasers, the integration of lasers into clinical dentistry and the safeguards as to their regulated use. [ABSTRACT FROM AUTHOR]

This paper focuses on minimizing the optical reflection on spherical fused silica lenses using femtosecond (fs) laser nanostructuring. A unique type of nanopillar formation has been observed on SiO 2 surfaces possessing antireflective properties when irradiated with a specific number of overlapping pulses, polarization, and fluence levels. Maintaining precise control over these sensitive technological parameters such as defocus and incident angle during the processing of geometrically complex shapes presents a significant challenge. This study proposes a theoretical optical arrangement to address this limitation by the design of a custom scanner system optimized for curved surfaces. The paper details the optimization process of such a bent image space (inverse-hypercentric) optical system using Zemax OpticStudio. Although the practical realization of the arrangement has not been performed, simulations are conducted to prove the functionality of the concept. Furthermore, we propose a practical method for segmented structuring of spherical surfaces based on consecutive repositioning and irradiation using an industrial robotic arm. By constructing the optical model, the necessary resolution of the segmentation has been calculated for a typical F-Theta scanner system and experimental verification has been performed. [ABSTRACT FROM AUTHOR]

The article reports that this issue of the journal introduces a revised list of sections and subsections, designed in close collaboration with the whole editorial board. The aim of these modifications is to reflect more faithfully the wide diversity of activities covered by the journal. A new section has been introduced as "Atomic and Molecular Collisions", it covers a large range of activities, from atom/atom or atom/molecules collisions including the very active field of ultra-cold collisions in laser-cooled atomic or molecular gases, to electron scattering and molecular reactivity.

The effects of neodymium:yttrium-aluminium-garnet (Nd:YAG) laser and silicon carbide (SiC) paper on the surface micro-topography of titanium-6 aluminium-4 vanadium (Ti6Al4V) alloy were examined in relation to the response of bone cells. The study was performed in three distinct stages: (1) after surface treatment of samples by laser and SiC paper, the surface hardness, surface roughness, corrosion resistance and surface tension were evaluated; (2) the growth of mouse connective tissue fibroblast cells (L-929) on untreated and treated samples was assessed in vitro; (3) the response of goat osteoblast cells to untreated and treated implanted samples was assessed in vivo. The surface roughness varied between 7 +/- 0.02 for laser-treated samples (LTSs) at 140 J cm(-2) and 21.8 +/- 0.05 for mechanically treated samples (MTSs). The surface hardness was found to vary from 377 Vickers hardness number (VHN) for MTSs to 850 VHN for LTSs. A corrosion potential of -0.21V was achieved for the LTSs compared with -0.51V for the MTSs. The LTSs exhibited a more hydrophilic behaviour (i.e. wettability) than did the MTSs. No cytotoxicity effect, unlike for the MTSs, was observed for the LTSs. The results of in vivo tests indicated longitudinal growth of osteoblast cells along the grooves on the samples formed by the SiC paper, and multidirectional spreading of the cells on the LTSs. [ABSTRACT FROM AUTHOR]

Optical beam propagation through the atmosphere is suffering from turbulence condition and scattering due to the refractive index effects on propagation. In this paper, we study optical beam propagation under the UAE's weather conditions. An outdoor test was carried out to gather the atmosphere parameters (temperature, wind, humidity, and refractive index) and feed them to a beam propagation model. The beam centroid was determined to study and predict the effects on it at different periods of the day. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (L-PBF) involves the coupling of multiple physical fields at different scales. Capturing the dynamic flow and thermal behavior of the melt pool during the L-PBF process through experimentation and predicting its quality is challenging, thus numerical simulation becomes a valuable method. The simulation results enable the prediction and assessment of the impact of material and process parameter changes on the quality of the final product. This paper reviews the methods for selecting appropriate models, performing simulation calculations, and analyzing the results. This paper makes several noteworthy contributions. It provides a comprehensive summary of the physical model, heat loss model, required heat source for simulations, and stresses generated within the melt pool. Furthermore, it explores the practical applications of L-PBF melt pool simulations, especially in defect analysis and the fabrication of complex structures. Finally, it concludes with an insightful analysis of the current trends in L-PBF simulations and outlines potential research directions to advance the development of melt pool simulations. [ABSTRACT FROM AUTHOR]

Spot size is an important parameter in laser-quality detection. However, the size of the spot is easily affected by environmental factors such as light. In this paper, we propose improved Kalman filter algorithms (IKF) with prior information to reduce the negative influence of noise on the spot size. At the same time, the filtering process and the method of determining the initial filter value are given. Finally, the experimental results on the synthetic dataset and real-world dataset confirm that the proposed IKF performs better than the compared methods. [ABSTRACT FROM AUTHOR]

Dual optical frequency combs have been a recurrent case of study over the last decade due to their wide use in a variety of metrology applications. Utilizing a single cavity laser to generate a dual comb reduces system complexity and facilitates suppression of common noise. However, a dual-comb regime in single cavity lasers tends to be more unstable and difficult to achieve. Therefore, having a better understanding about the way they are generated could improve and automate their generation and control. In this paper, we investigate the build-up dynamics and collision of dual comb in a polarization-multiplexing ring-cavity fiber laser using DFT (Dispersive Fourier Transform) method. We observe a bunch of meta-stable short-lived mode-locking states before the laser entered the dual-comb mode-locking state. The energy level of this short-lived initial pulses determines its evolution. If it decreases too much, the pulse will eventually collapse while if it stays above certain level, it will be successfully generated. The results presented in this paper increase the understanding of dual-comb generation inside a single cavity laser and may contribute in future attempts to increase the stabilization of this regime. [ABSTRACT FROM AUTHOR]

The paper presents the dynamic impact properties of laser-sintered polyamide PA2200 in accordance with the building orientation. The idea of deTermining the impact properties in relation to building orientation lays on orientation-property dependence founded in our previous studies of tensile, bending and fracture mechanics testing. The specimens were manufactured under the same energy density and temperature conditions, at four orientations, as described in the paper content. The experimental investigation was carried out on a pendulum impact testing machine to deTermine the impact energy and strength according to the building orientation. Brittle fracture was observed for all specimens, independent of building orientation, and a similar behavior was also observed in the elastic zone of deflection. However, impact strength and impact energy are influenced by orientation. [ABSTRACT FROM AUTHOR]

This paper analyzes the tribological behavior of the Ti6Al4V ELI alloy subjected to laser texturization for medical purposes. Laser texturing enables one to observe specific patterns of the material surface at established depths. Microtexturing of the samples was performed using a 355 nm picosecond laser. The influence of the microtexturing process (depending on the process parameters) on the geometric parameters of the proposed laser texturing pattern was evaluated. Selected samples were subjected to tribological testing using the ball-on-plate technique in dry and lubricant-sliding methods (in Ringer solution). The wear properties were evaluated by comparing the coefficient friction, wear volumes, and wear ratio. A scanning electron microscope characterized the morphologies of the wear scar and the wear mechanism. The experimental results show that the surface texturing and the changes in microgrooves can reduce wear. The results indicate, that samples after laser texturing were characterized by 15% higher microhardness, compared to those in the initial state. It was found, a 26% reduction in friction coefficient and 29% in the wear volume compared to the smooth, untextured surface samples under lubricated conditions. The decrease in value of the coefficient friction and wear volume for the samples after the laser texturing process is an effect of synergistic of entrapped wear debris in micro-grooves and increased hardness for samples after laser textured. [ABSTRACT FROM AUTHOR]

In this paper, we employ the quantum trajectory Monte Carlo model to simulate the momentum distribution of Argon atoms during tunneling ionization. Our analysis illustrates the use of semi-classical models to study the changes in electron trajectories under different laser field intensities. And by studying the different subcycles, the changes of the interference pattern are observed. Our approach successfully observes the interference patterns resembling fishbone and spider stripes. We delve into the subperiodic interference structures present in the photoelectron momentum distributions. Specifically, we investigate the correlation effects of ionization trajectories on the interference fringes within the same period and in adjacent periods. Our analysis demonstrates that the holographic interference fringe results from the superposition of direct ionization trajectories and scattering trajectories. We elucidate the mechanisms underlying the formation of above-threshold ionization (ATI) ring structures and temporal double-slit interference patterns. Additionally, we investigate how wave packets perceive the Coulomb potential and its impact on interference phenomena under varying field intensities. Notably, without the Coulomb potential, the original spider-like holographic interference pattern disappears, replaced by temporal double-slit interference fringes similar to those observed within a comparable time frame. [ABSTRACT FROM AUTHOR]

Heritage buildings represent history and act as vessels of human civilisation. The significance of these architectural phenomena increases as society increases, which renders their preservation and ethical use increasingly crucial. Hence, preserving heritage buildings is necessary for societal benefit. The accuracy of three-dimensional (3D) point cloud models of heritage buildings is important to their digital conservation. Traditional mapping methods typically require more time and human resources. Furthermore, the outcome is subject to measurement omissions, errors, and other issues, which are contrary to the protection of the object measured. The complex elements of ancient Chinese architecture render it challenging for traditional measuring techniques to accurately capture spatial structural information. The 3D laser scanning technology is a novel technology to obtain 3D data rapidly. In this paper, the Great Achievement Palace of the Confucian Temple in Yuci District, Jinzhong City, Shanxi Province, was used as an example to examine the application of 3D laser scanning technology to acquire point cloud models of heritage buildings. Field data collection for architectural heritage using 3D laser scanning technology requires measuring station setting analysis to ensure effect accuracy while considering the elements of target location and quantity. For the 3D point cloud model of the Great Achievement Palace, error analysis and accuracy assessment were conducted on the quality elements of alignment accuracy between scanning stations, point cloud model reliability, point cloud data noise condition, and whether the point cloud data were stratified. The findings demonstrated that the improved method quickly and accurately acquired 3D point cloud model data and obtained realistic spatial data models of the heritage building. [ABSTRACT FROM AUTHOR]

The Magnetic Pulse Compression (MPC) system is a well-established method for generating high-peak-power, short-duration voltage pulses, commonly used in pulse power supplies (PPS). Traditionally designed for a fixed high repetition rate, this paper explores the techniques and outcomes of variable repetition rate operation in an MPC-based PPS used to excite a copper vapor laser (CVL). Specifically, the PPS, initially designed for 9 kHz operation, is tested at three different rates: 8 kHz, 9 kHz, and 10 kHz. A mathematical model is developed, and experimental modifications are presented in this paper. The study investigates the impact of repetition rate variations on CVL parameters, particularly phantom current (Phantom current: 47% at 8 kHz, 54% at 9 kHz, and 51% at 10 kHz). Phantom current reduces at 10 kHz due to improved impedance matching. At 8 kHz, the laser output is 24W, increases to 30W at 9 kHz and 43W at 10 kHz with a plane-plane resonator configuration. This trend extends to the master oscillator power amplifier (MOPA) at 10 kHz, resulting in a 50% increase in optical power output compared to 9 kHz. This improvement at 10 kHz applies to various parameters, including optical pulse characteristics, average power, electro-optic efficiency, energy per pulse, reduced jitter, and impedance matching. [ABSTRACT FROM AUTHOR]

In this paper, we report a multi-wavelength passively Q-switched fiber laser based on reconfigurable Lyot ring filter (RLRF) and Erbium-doped fiber (EDF) saturable absorber (SA). The gain saturable absorption characteristics of the EDF are analyzed in the experiments. When EDF is used as SA, EDF exhibits different nonlinear characteristics at different pump powers. Through the observation of the experimental data, we discuss the relationship between the multi-wavelength and passively Qswitching, in view of the position of the wavelength excitations and the presence or absence of the corresponding pulse sequence. The RLRF in the structure uses a 2 m long polarization maintaining fiber (PMF), and the wavelength interval between 1.5 and 3.0 nm can be effectively switched by adjusting the polarization controller (PC). The laser elaborated can flexibly switch from a single to seven wavelengths, with a corresponding pulse repetition rates of 24.11 – 59.38 kHz, a minimum Qswitched pulse width of 1.16 μs, a maximum average output power of 46.98 μW, and a maximum single pulse energy of 9.64 nJ. [ABSTRACT FROM AUTHOR]

Objectives and Scope.Supercontinuum generation is not only one of the most exciting topics in modern laser physics; this is the area where high-field science in the most amazing way meets the physics of low-energy unamplified ultrashort pulses. Although the strong-field chapter of the supercontinuum-generation story was opened back in the 1970s, and has been overviewed in a comprehensive and illuminating way in the famous book The Supercontinuum Laser Source edited by R. Alfano (Springer-Verlag, New York, 1989), many interesting and physically important aspects have been added to this part of the supercontinuum story in the past few years, as laser pulses have become shorter and shorter, while computers and computer codes, on the other hand, have become more and more powerful and sophisticated. The rapid technical and conceptual progress in microstructure fibers has recently resulted in the appearance of a whole family of fibers, such as photonic-crystal, holey, and tapered fibers, capable of generating supercontinuum emission with unamplified, nano- and even subnanojoule femtosecond pulses, leading to revolutionary changes in frequency metrology and opening new horizons in ultrafast science, short-pulse control, and spectroscopic and biomedical applications.As a physical phenomenon, supercontinuum generation involves the whole catalogue of classical nonlinear-optical effects, such as self- and cross-phase modulation, four-wave mixing, stimulated Raman scattering, and many others, which add together to produce emission with extremely broad spectra, sometimes spanning a couple of octaves. It is, therefore, a challenging task to develop an adequate physical model for this phenomenon based on an understanding of all its nonlinear-optical ingredients. Such a model may, perhaps, show ways of generating few-cycle and subcycle light pulses in a simple and compact fashion, making these pulses a routine tool for everyday experiments, not only in physics but also in... [ABSTRACT FROM AUTHOR]

Comments on the article 'Soliton Laser: Geometry and Stability,' by A. Yu. Okulov, which appeared in the volume 89, 2000, issue of the 'Optics and Spectroscopy' journal. Solutions of the master equation for the field envelope in a laser with a self-imaging cavity; Analysis of stability against weak perturbations; Proof of instability absed on the theory developed by Zel'dovich and Barenblatt.

In this paper, a structured light vision measurement method using a scanning laser line and a positioning laser line is proposed. The novel method enables the scanning laser plane to slide along a slide rail while maintaining intersection with the positioning laser plane, eliminating the need to determine the scanning direction and moving step. During the measurement process, the laser plane equations need to be recalibrated for each new position, so a real-time calibration method is given. Initially, the geometric barycenter method is employed to detect the subpixel coordinates of the light stripe intersection point. Subsequently, these coordinates are projected into the camera coordinate system using the initial equations of the positioning laser plane. Finally, leveraging the normal information of the initial equation of the scanning laser plane and the three-dimensional coordinates of the light stripe intersection point, the real-time calibration of the scanning laser plane equations can be accomplished. The proposed method enables the three-dimensional reconstruction of objects, and its accuracy is verified through measurements on gauge blocks. Experimental results demonstrate that this method achieves precise and stable three-dimensional reconstruction of object surface shape. [ABSTRACT FROM AUTHOR]

In the future, the goal of service robots is to operate in human-centric indoor environments, requiring close cooperation with humans. In order to enable the robot to perform various interactive tasks, it is necessary for robots to perceive and understand environments from a human perspective. Semantic map is an augmented representation of the environment, containing both geometric information and high-level qualitative features. It can help the robot to comprehensively understand the environment and bridge the gap in human-robot interaction. In this paper, we propose a unified semantic mapping system for indoor mobile robots. This system utilizes the techniques of scene classification and object detection to construct semantic representations of indoor environments by fusing the data of a camera and a laser. In order to improve the accuracy of semantic mapping, the temporal-spatial correlation of semantics is leveraged to realize data association of semantic maps. Also, the proposed semantic mapping system is scalable and portable, which can be applied to different indoor scenarios. The proposed system was evaluated with collected datasets captured in indoor environments. Extensive experimental results indicate that the proposed semantic mapping system exhibits great performance in the robustness and accuracy of semantic mapping. [ABSTRACT FROM AUTHOR]

Laser drilling is capable of reducing drilling costs and time. In laser drilling, a high rate of penetration (ROP) can be achieved, and the hole is cased due to laser interaction once it is drilled. In addition, laser technology can substitute conventional perforation techniques with no formation damage. Rock cutting with a laser beam is affected by various variables that fall within three categories; the rock parameters, purging system and experimental setup, and laser parameters. Each set of these categories affects the rock lasing process. Formation parameters include rock type, sample size, orientation, and the type of fluids saturating the rock sample. The purging system parameters include the type of purging system, application parameters, and the purging medium. Laser parameters involve laser type, laser application mode, beam power, duration, intensity, and frequency. This paper reviews several experimental works performed by institutes, researchers, and entities to provide the reader with a comprehensive knowledge base for further experimental work, modeling for laser drilling, and studies. Because performed laser drilling experimental work is huge and covers tremendous aspects, only the purging system and effect of formation parameters were considered in this review, while laser parameters will be presented in a later paper. Results showed that the laser can drill swiftly through all rock types in conventional vertical, directional, or horizontal drilling. For optimum laser drilling, the purging system and its parameters must be carefully chosen, including the type of system, purging gas, gas pressure, distance to the lased sample surface, and the purging angle. The optimum purging system uses nitrogen as a purging fluid. [ABSTRACT FROM AUTHOR]

In this paper, a new laser linkage processing method based on trajectory distribution of galvanometer and mechanical servo system is proposed to achieve large-range high-feedrate laser processing. The proposed method can effectively improve the processing range, accuracy, and efficiency. Firstly, according to the processing trajectory characteristics of the galvanometer and mechanical servo system, a trajectory distribution filter algorithm is designed to reasonably distribute the interpolated trajectory to the equipment. Then, two linkage processing methods are designed based on off-line trajectory and real-time trajectory distribution. Moreover, an experimental platform consisting of the laser, galvanometer, and mechanical servo system is built, and experiments are performed on experimental equipment to verify these methods. Finally, the experimental data is collected at different processing feedrates, and the processing errors of two linkage processing methods and mechanical servo system processing are calculated and compared. The processing accuracy and effect of linkage processing are effectively improved. In addition, the processing effect of real-time trajectory distribution is also improved compared to the off-line trajectory distribution, which is simpler and easier to implement. These methods have been successfully applied to the large-scale high-feedrate laser processing equipment in the laboratory. [ABSTRACT FROM AUTHOR]

The article lists papers that will be published in the volume 75, number 10 issue of the "Journal of Optical Technology" in October 2008. They include "Phase Modulation of Femtosecond Light Pulses with the Spectra Superbroadened in Dielectrics with the Normal Group Dispersion," "Methods of the Superbroadband Terahertz Pulse Generation in Femtosecond Lasers," and "Feasibility of the Use of Fourier Holography in the Creative Thinking Simulation Problem."

Stretchable displays attract significant attention because of their potential applications in wearable electronics, smart textiles, and human-conformable devices. This paper introduces an electrically stable, mechanically ultra-robust, and water-resistant stretchable OLED display (SOLED) mounted on a stress-relief pillar platform. The SOLED is fabricated on a thin, transparent polyethylene terephthalate (PET) film using conventional vacuum evaporation, organic-inorganic hybrid thin film encapsulation (TFE), and a nonselective laser patterning process. This simple and efficient process yields an OLED display with exceptional stretchability, reaching up to 95% strain and outstanding durability, enduring 100,000 stretch-release cycles at 50% strain. Operational lifetime and water-resistant storage lifetime measurements confirm that the TFE provides effective protection even after the nonselective laser patterning process. A 3 × 3 array SOLED display module mounted on a stress-relief pillar platform is successfully implemented, marking the first case of water-resistant display array operation in the field of SOLEDs. This work aims to develop practical stretchable displays by offering a reliable fabrication method and device design for creating mechanically robust and adaptable displays, potentially paving the way for future advances in human-conformable electronics and other innovative applications. [ABSTRACT FROM AUTHOR]

The study of the complex model associated with chaotic models is always the most complicated and fundamental in the current scientific environment. The primary goal of the current paper is to provide an illustration of the fundamental theory while analysing dynamical systems and validating the chaotic behaviour of the Lorenz–Haken (LH) equations, a system of fractional differential equations. The LH equations are used to describe the 4D chaotic laser. The Adams–Bashforth numerical method is used to extract the numerical solutions projected model. The classical model introduces the bifurcation of the parameter linked with the system. The system's uniqueness and existence are confirmed using the fixed-point hypothesis with the Caputo–Fabrizio fractional operator, followed by boundedness and dynamical analysis. Furthermore, the chaotic character of the numerical solutions with different orders obtained at different beginning circumstances is presented. [ABSTRACT FROM AUTHOR]

The beam self-cleaning phenomenon is theoretically predicted by the two-dimensional nonlinear Schrödinger equation, which describes self-focusing, and is observed in the case of femtosecond laser filamentation in the collimated regime of propagation. However, the impact of external focusing on the self-cleaning has not been investigated so far. In this paper we systematically study this impact in a wide range of focusing conditions. We show that the energy range, in which self-cleaning can be observed, shrinks monotonically with the numerical aperture growth at some point vanishing at all. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to solve a series of problems, such as the difficulty in accurately controlling the specific surfaces, and the interference between the laser beam and the part, when the laser is used to clean mechanical parts with complex surfaces by using robots. Firstly, a region segmentation algorithm of the stereo lithography (STL) model was designed, and the feature surfaces of the model were obtained by using the dihedral angle as the criterion. Then the path points which could easily cause interference between the laser beam and the part to be cleaned were detected by the method of ray intersection, and the pose of the robot was modified according to the normal vectors of two non-interference points that were adjacent to the continuous interference points respectively. Finally, the proposed method was validated by scanning path visualization and robot laser cleaning process experiments. The generated path in the unit of feature surface according to the variation components of normal vectors proved the effectiveness of the STL model region segmentation algorithm based on dihedral angle division criteria; the change of the normal vectors of the path points on the current feature surface was continuous and smooth, which meant that the path points did not cause sudden change of the robot pose after the pose correction. The robot cleaned the specific surfaces of the test workpiece safely and effectively in the actual laser cleaning experiments, and the effective cleaning area reached 96.87%, 99.56%, 94.53% and 91.62% of the target cleaning area, which further proved the effectiveness of this study. The method is also useful for the path planning of robots in other processing fields. [ABSTRACT FROM AUTHOR]

In the last decade, methods for relief fabrication on the metal surfaces by using the same base metal itself have appeared. The fabrication of surface relief by the laser remelting process is based on the relocation of the molten state of the base material instead of its removal. Since remelting is a thermally driven process, significant differences on the mechanical characteristics after surface structuring can be expected due to their thermophysical properties. Such operations are usually performed with high power radiation sources and in environments enriched with protective gases. In this paper, we have used relatively affordable low power equipment for relief formation on the carbon steel surface in air at room temperature. Within the framework of our investigation, we researched two means of relief formation based on the displacement of the liquid phase during laser irradiation. We found that the process of laser relief formation is accompanied by the generation of high amounts of oxide. This compromises the mechanical characteristics of the relief. Moreover, in this paper a multipass technique that enables the formation with a low amount of oxides is proposed. [ABSTRACT FROM AUTHOR]

A carbon fiber-reinforced thermosetting plastic and stainless steel were joined by the fiber laser. The surface texture effect on the joint was investigated. The abrasive paper scratching is shown to form single directional striae on stainless steel with intermittent ridges. Laser texture processing creates uniformly distributed microdimples and ridges, which forms a rectangular cellular structure. This processing can improve the fluidity of molten polyphenylene sulfite during laser joining. Laser scanning on stainless steel results in the formation of fusion and heat-affected zones. In the heat-affected zone, lathy ferrite is located along the boundary, while in the fusion zone, ferrite forms the skeletal structure and separates austenite into a cellular structure. The surface texture modification can contribute to the adhesive strength between stainless steel and polyphenylene sulfite through on enlarged contact surface area by forming striae, microdimples, and ridges. As compared to the abrasive paper scratching, the stainless steel/plastic joint with laser texture processing exhibits a higher shear strength. [ABSTRACT FROM AUTHOR]

Weld seam recognition is critical for providing information for automated welding control, promoting the advancement of welding sensing technology, and improving welding manufacturing automation. The extraction of the square groove's feature points using a new method is presented in this paper. Noise is produced in significant quantities due to the difficult method used to acquire the weld image. To process images, a specific method must be utilized. In this work, the central line of the laser stripe is extracted based on Canny edge detection with Haralicks facet model. Based on the central line, the Förstner algorithm is used to recognize the corner points of the square weld groove. Following the establishment of a test platform, a series of detection tests for various sizes of the square groove is established. The acquired detection results are sufficiently accurate, with maximum relative errors of less than 3.19%, demonstrating the rationale of the suggested visual sensor's physical design and the validity of the proposed detection algorithms. [ABSTRACT FROM AUTHOR]

The article discusses the study of Ulli Eichman and colleagues of Max Born Institute in Berlin, Germany on the acceleration of neutral atoms using a strong laser pulse. It notes that Eichman and colleagues have used helium atoms in their experiment because of its atomic featherweight that can easily be push around with strong forces, and reveals that it has survived the strong laser. It mentions that its survival was because of the ability of helium's electron to oscillate near its ionic core.

Research on irregular stone masonry walls is hampered by the lack of detailed geometrical models of their internal micro-structure, i.e. the shape and size of each stone and its position within the wall. Without such a geometric digital twin of walls tested in the laboratory, it is difficult to evaluate the accuracy of existing numerical simulation techniques. Here, we describe the generation of geometrical digital twins of three irregular stone masonry walls built in the laboratory. We labelled each stone manually and then obtained the geometry of the individual stones using a portable laser scanning device. With the same device we scanned the wall after the construction of each layer. We then registered the position of each stone in the layer. This paper outlines the methodology for the data acquisition and digital reconstruction and presents the datasets for the walls. The developed geometrical digital twins provide unique information regarding the micro-structure of constructed walls that is key for the development and validation of numerical simulation techniques for stone masonry. [ABSTRACT FROM AUTHOR]

In this work, the attainment of a high chirp rate random microwave waveform by using two port Lithium Niobate Mach Zehnder Modulator is reported and also experimentally verified. Numerous techniques are in trend to produce the chirp microwave signals where temporal pulse shaping is the most commonly used technique. Range-Doppler resolution of a radar system can be improved using the chirp microwave waveform by improving the chirp rate, time bandwidth product, and central frequency. In this paper, the author reported and successfully experimentally verified the dependency of chirp bandwidth and chirp rate on Laser Frequency and RF signal generator. We used a feasible and straight forward method of producing chirped arbitrary microwaves by using the external optical modulator. At the end of the paper, authors are able to compute the chirp rate, 3 dB bandwidth, OSSR, RFSSR value, and central frequency. It is shown that the experimentally obtained results match with the simulation data within the experimental limits. [ABSTRACT FROM AUTHOR]

In this paper, we report a diode side-pumped injection-seeded single-frequency Tm,Ho:YLF laser, which operated at lasing threshold and emitted at 2051.2 nm. The assistance of Fabry–Pérot (FP) etalons to seed injection via mode selection was investigated. An acousto-optic Q-switched output of 6.7 mJ was achieved at 5 Hz. A temporal pulse duration of 310 ns with spectral linewidth of 2.0 MHz and frequency stability of 0.8 MHz root-mean-square (rms) was detected. The beam profile was a high-quality Gaussian TEM00 mode with M2x/y of ~ 1.15/1.14. This 2 μm laser source would be a good candidate for ground-based wind-detection coherent Lidar system. [ABSTRACT FROM AUTHOR]

This paper provides a detailed analysis of transverse mode degeneracy process of end-pumped Nd: YVO 4 laser. By observing the intersection of the beat frequency signals in the concave-plano cavity, the exact cavity length position of the transverse mode degeneracy can be clearly identified, which is also where transverse-mode locking occurs. Investigating the positions of the degeneracy of 1/3 and 2/7 reveals that transverse-mode locking occurs within the micrometer range. Our results give a simple and intuitive description of frequency degeneracy in a common solid-state laser [ABSTRACT FROM AUTHOR]

In this paper, a numerical model is presented for the simulation of melting and microstructure formation during a layer-by-layer laser melting process. The model couples the solution of thermal and species transport with a sharp-interface enthalpy-based phase change model to track the melting and solidification in each layer. The effect of the moving laser energy source is implemented through a transient moving heat flux boundary condition. Transition from the completion of a layer to the start of a new layer is implemented using a domain translation technique, keeping the size of the computational domain constant. The model captures the remelting of a previous layer during the formation of a new layer. Simulations are performed to predict the segregation and grain structure formation during multi-layered laser melting of Al-10%Cu alloy. It is seen that the laser scan direction governs the grain orientation with grains growing in the direction of laser travel. Also, the remelting of the previously formed grains in the adjacent layer affects the species concentration and grain structure in the subsequent layer. Higher power, lower laser scan speed, and smaller laser radius leads to the formation of longer grains with larger aspect ratio spanning multiple layers. [ABSTRACT FROM AUTHOR]

To study the influence of different cleaning methods on the corrosion resistance of 316L stainless steel surface, this paper carried out polarisation curves and electrochemical impedance spectroscopy studied on the uncleaned, acid pickling cleaning, and picosecond laser cleaning samples. The surface morphology of the samples after electrochemical testing was detected by laser confocal microscopy and scanning electron microscopy, and then the electrochemical corrosion behaviour of the samples in 3.5% NaCl solution was analysed under different cleaning methods. The results show that compared with the uncleaned sample, the corrosion potential of the sample after picosecond laser cleaning was relatively improved. At this time, the corrosion current density was as low as 2.29 × 10–6 A/cm2, the polarisation resistance value was as high as 18615 Ω·cm2, the impedance modulus was as high as 5.5 × 105 Ω, and the capacitance-impedance radius reached the maximum value. In conclusion, the corrosion resistance of the sample after picosecond laser cleaning was better. [ABSTRACT FROM AUTHOR]

In this paper, the end-pumped passively Q-switched Nd: KGW/Cr4+:YAG self-Raman laser is designed to achieve high efficient operation. Concave-plane linear cavity is adopted to obtain the shortest cavity length, and long Nd: KGW crystal of 40 mm is used in the experiment. Cr4+:YAG crystals of high initial transmittances (T0 = 96% and 92%) are utilized to realize efficient and stable passively Q-switched operation. The passively Q-switched Nd: KGW/Cr4+:YAG self-Raman laser is theoretically investigated at 1181 nm corresponding to the Raman mode of 901 cm− 1 shift in Nd: KGW crystal. With Cr4+:YAG crystal of the initial transmittance T0 = 96%, the maximum output power of 0.624 W at 1181 nm is achieved experimentally with optical-to-optical efficiency of 13.9%, which is the highest efficiency reported for passively Q-switched Nd: KGW self-Raman laser. [ABSTRACT FROM AUTHOR]

Aiming at the problems of high material cost, difficult performance enhancement and complicated manufacturing process of the traditional subtractive manufacturing method for rotary die-cutting tools, this paper takes rotary die-cutting tools as the object and prepares Ni45A/TiC coatings with different TiC contents on the basis of Ni45A coatings as the transition layer to achieve the optimization of the performance of fusion-cladding layer and defect control. The mixed-level orthogonal design was combined with regression analysis to explore the effects of process parameters and TiC powder ratios on the properties and defects of coatings. Following multi-objective optimization, the optimal process parameters were 60wt.% TiC, 1.8 kW laser power, 4 mm/s scanning speed, and 10 L/min gas flow rate. Compared to the optimal outcomes of the orthogonal tests, the validation test saw an increase in the coating's hardness from 1200.2 HV to 1219.6 HV and a decrease in wear volume from 0.546 × 10−3 mm3 to 0.503 × 10−3 mm3. The error of the predicted and verified gray correlation degrees was 1.296%. The research provides a theoretical basis for laser additive manufacturing of high performance rotary cutting tools and technical support for additive manufacturing of curved substrates. [ABSTRACT FROM AUTHOR]

High-power lasers develop high energy per unit time, and as energy curves space, we expect atomic energy levels to change. The fluorescence spectrum is a good measurement of the matrix elements involved in the Rabi oscillation and consequently allows us to determine the scalar curvature. At high Z, electrons oppose ionization even for strong intensities. Because high-power lasers address relativistic atoms, the wave functions involved must be solutions of the Dirac equation in a curved space-time. The paper can be seen as a way to check whether the Einstein's gravitational theory is valid in the dimension of laboratory. [ABSTRACT FROM AUTHOR]

Apple is usually damaged by mechanical factors, including harvesting methods and transportation. The mechanical damage to apples induces great economic loss every year. Current methods can only conduct qualitative determination for apple injection. Fuji apple damage detection method based on relaxation single-wavelength laser (RSWL) and convolutional neural network (CNN) was proposed in this paper. Red Fuji apple was selected as research object, and RSWL detecting system was designed and fabricated. The laser intensity was controlled by a laser current driver. RSWL measurement data of apple samples was obtained and processed by SNV and MSC algorithms. CNN was utilized to establish apple damage determination model. Results indicated that RSWL signals could discriminate apples with different mechanical damage. MSC algorithm presented better damage discrimination effects than SNV algorithm. The prediction accuracy of MSC is 93%. RSWL combined with CNN proposed in this paper has some advantages, including small volume, easy operation, and low price. It provides a novel way for fruit damage fast determination. [ABSTRACT FROM AUTHOR]

In mining safety and other fields, similar material simulation is the main research method to study the movement and deformation of rock formation and ground surface. However, the inaccurate subsidence laws could be obtained because the strength of the composition materials like gypsum and lime is easily affected by moisture. Therefore, it is crucial to monitor the moisture content when carrying simulation experiments. This paper discussed the feasibility of indirectly measuring the moisture content of similar material models using the three-dimensional (3D) laser scanning reflection intensity through three experiments on similar material specimens. The results showed that the laser reflection intensity was sensitive to the moisture content, incidence angle, and distance with three different relationships and the influence of the two factors could be weakened through the established correction models. However, it was recommended restricting the incidence angle to less than 20° and setting the distance from 4 to 10 m to reduce the complexity of correction. The accuracy of this method reached 1.1% under the monitoring condition of 4 m and the normal incidence, which could meet the requirements for monitoring the moisture content of similar material models. The research results of the paper provide a new method to monitor the moisture content in similar material models. [ABSTRACT FROM AUTHOR]

The experimental results in studying lasing and pumping parameters of the CuBr laser with attypical excitation mode are presented in the paper. The excitation was provided by the single pulse mode with preliminary preparation of the active medium by pulse sequence (zug). The effect of the time delay between pulse sequence and single excitation pulse on the CuBr + Ne and CuBr + Ne + HBr media lasing was determined. It has been established that an increase in this time delay leads to an increase in the duration of the generation pulse. It was shown for the first time that lasing in a CuBr + Ne + HBr laser can be obtained with a relaxation time of the active medium up to 5 ms. The critical electron concentration which provides ability of generation for CuBr + Ne and CuBr + Ne + HBr media was experimentally shown. [ABSTRACT FROM AUTHOR]

To optimize the hole-making process and minimize the cost of time and other expenses, this paper explores femtosecond laser trepanning drilling of K24 alloy, focus on the control of the laser process parameter groups on the diameter, circularity, taper and material removal rate (MRR) for the micro-hole formation. The laser power, repetition rate, focal position, and cutting speed are selected as independent design factor for Taguchi orthogonal array with four levels employed to design and conduct the experiments. The effect of laser parameters on processing performance is evaluated in terms of both mean response and signal-to-noise (S/N) ratio, which are used to investigate the effect of the levels of the four process variables on the results in order to optimize and control the output. The experimental results reveal that the exit circularity, taper and MRR are affected mainly by the laser power. In addition, the entrance diameter increases with the laser power, and the exit diameter is decreased with the cutting speed increasing. However, the repetition rate has no significant effect on the above processing performance within the range of values investigated. Finally, the experimental results verified that the optimized laser hole–making parameters can improve the shape and dimensional accuracies of the obtained micro-holes. This optimized combination of laser processing parameters provides an effective method to improve the hole-making quality and efficiency. [ABSTRACT FROM AUTHOR]

In this paper, a new laser shock microforming method, laser shock sheet bulk microforging (LSSBMF), is put forward on the basis of the merit of sheet bulk forming and laser shock microforming. In this study, AZ31B magnesium alloy workpieces with different grain sizes, workpieces with different thicknesses, and microgroove dies with different widths are selected to evaluate the size effects on the forming properties. In the experiment, the influences of laser loading on grain size, grain size on depth of forming, and microhardness are studied. In the numerical simulation, the die geometry and workpiece size effects on the material forming process are analysed. The research results show that under the same laser energy loading, the larger the grain size is, the more obvious the grain size refinement phenomenon is. The forming depth increases with growing grain size, whereas the microhardness decreases. Numerical simulation results indicate that under the same laser energy loading, workpiece forming depth decreases with growing die feature groove width, whereas the equivalent plastic stress increases. The equivalent plastic stress increases with increasing workpiece thickness, whereas the forming depth decreases. [ABSTRACT FROM AUTHOR]