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Rb <sub/>10</sub> Zn <sub/>4</sub> Sn <sub/>4</sub> S <sub/>17</sub> : A Chalcogenide with Large Laser Damage Threshold Improved from the Mn-Based Analogue
摘要： In the military and civilian fields, with the development of new technologies, high-powered nonlinear optical (NLO) crystals demonstrate broad application prospects. For purposes of designing a better NLO material, a new chalcogenide Rb10Zn4Sn4S17 was successfully designed with a high temperature solid-state method on the basis of previously reported compound Sr3MnSn2S8. The experimental results indicate that Rb10Zn4Sn4S17 possesses a prominent band gap of 3.59 eV, compared with the laser damage threshold (LDT) of Sr3MnSn2S8 (3 times that of AgGaS2); Rb10Zn4Sn4S17 shows an outstanding LDT about 5 times that of AgGaS2. Meanwhile, it has an ideal second harmonic generation (SHG) response approximately 0.7 times that of AgGaS2.
关键词： second harmonic generation (SHG),laser damage threshold (LDT),chalcogenide,nonlinear optical (NLO) crystals
更新于2025-09-19 17:13:59
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Dynamic behavior modeling of laser-induced damage initiated by surface defects on KDP crystals under nanosecond laser irradiation
摘要： the issue of laser-induced damage of transparent dielectric optics has severely limited the development of high-power laser systems. exploring the transient dynamic behaviors of laser damage on KDp surface by developing multi-physics coupling dynamics model is an important way to reveal the mechanism of nanosecond laser damage. In this work, KDP crystals are taken as an example to explore the mechanism of laser-induced surface damage. Based on the theories of electromagnetic field, heat conduction and fluid dynamics, a multi-physics coupling dynamics model is established for describing the evolution of nanosecond damage processes. The dynamics of laser energy transmission, thermal field distribution and damage morphology during nanosecond laser irradiation are simulated with this model. it is found that the enhancement of light intensity caused by surface defect plays an important role in the initial energy deposition and damage initiation of the laser irradiation area. The evolution of temperature field and crater morphology during subsequent laser irradiation is helpful to understand the laser damage process. The feasibility of this model is verified by the morphology information of typical defect-induced laser damage. this work provides further insights in explaining the laser-induced damage by surface defects on KDp crystals. the model can be also applied to investigate the laser damage mechanisms of other transparent dielectric optics.
关键词： laser-induced damage,multi-physics coupling model,nanosecond laser irradiation,KDP crystals,surface defects
更新于2025-09-19 17:13:59
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Ultra high damage threshold optics for high power lasers
摘要： The output energies of lasers have increased year-by-year since their invention. Compared to this increase of laser energies, the damage threshold of optical components has not strongly changed. Therefore, the size of optics in high-energy laser system increases. This situation could change dramatically if optics with higher damage threshold were developed. Here, we propose a high damage threshold optics using a neutral gas as an active medium. More than 95% diffraction ef?ciency has been achieved. The damage threshold for a 6 ns laser pulse is measured to be 1.6 kJ/cm2. The aperture size of the present system is about 60 mm2. Based on this result, we anticipate that control of a 1 kJ laser beam may be achievable using 1 cm sized optics, driven by a < 50 mJ ultraviolet laser, making this scheme promising in high power laser applications.
关键词： damage threshold optics,ultraviolet laser,high power lasers,diffraction efficiency,neutral gas
更新于2025-09-19 17:13:59
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Surface Morphological Features of Molybdenum Irradiated by a Single Laser Pulse
摘要： Molybdenum (Mo) is considered a plasma facing material alternative to tungsten (W) for manufacturing the divertor armours of International Thermonuclear Experimental Reactor (ITER). Transient thermal loads of high energy occurring in a tokamak during the service life have been simulated through a single laser pulse delivered by a Nd:YAG/Glass laser, and the effects have then been examined through scanning electron microscopy (SEM) observations. An erosion crater forms in correspondence with the laser spot due to the vaporization and melting of the metal, while all around a network of cracks induced by thermal stresses is observed. The findings have been compared to results of similar experiments on W and literature data. The morphology of the crater and the surrounding area is different from that of W: the crater is larger and shallower in the case of Mo, while its walls are characterized by long filaments, not observed in W, because the lower viscosity and surface tension of Mo allow an easier flow of the liquid metal. Most importantly, the volume of Mo ablated from the surface by the single laser pulse is about ten times that of W. This critical aspect is of particular relevance and leads us to conclude that W remains the best solution for manufacturing the armours of the ITER divertor.
关键词： laser,nuclear fusion reactors,surface damage,molybdenum,microstructure
更新于2025-09-19 17:13:59
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Analytical solutions of thermal damage in living tissues due to laser irradiation
摘要： In this article, the analytical solutions of dual-phase-lag (DPL) bio-heat equation with various boundary conditions have been constructed for curative therapy of cancerous cells. The volumetric thermal source components in the model of DPL bioheat transfer, such as the metabolic heat generation and the rate of blood perfusion, are considered. The analytical solutions in the Laplace domain are obtained. The thermal injuries to the tissue are assessed by the denatured protein range, using the formulation of Arrhenius. Numerical outcomes for temperatures are graphically introduced. A parametric analysis is devoted to the identification of an appropriate procedure for selecting important design variables in order to predict more accurate to reach effective heating in hyperthermia treatment.
关键词： thermal damage,dual-phase-lag model,Bioheat transfer,living tissue
更新于2025-09-19 17:13:59
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LiBa <sub/>4</sub> Ga <sub/>5</sub> Q <sub/>12</sub> (Q = S, Se): Noncentrosymmetric Metal Chalcogenides with a Cesium Chloride Topological Structure Displaying a Remarkable Laser Damage Threshold
摘要： The exploration of novel infrared nonlinear optical (IR NLO) materials with large second-harmonic generation (SHG) responses and wide band gaps has become very imperative recently. Herein we reported two noncentrosymmetric compounds, LiBa4Ga5Q12 (Q = S, Se), crystallizing in space group P421c (No. 114), which feature 3D frameworks built by a basic [Ga5Q16]17? windmill cluster and LiQ4 tetrahedra in a cesium chloride topological structure. Both compounds satisfy the desired balance between good SHG responses (～1.5× that of AgGaS2) and wide band gaps (3.43 and 2.44 eV) with remarkable laser damage thresholds (21× and 6× that of AgGaS2). The theoretical calculations uncover that the [Ga5Q16]17? cluster makes major contributions to the SHG e?ect in LiBa4Ga5Q12. In addition, the structure?performance relationship among all compounds in the I?II4?III5?VI12 system has been discussed systematically, which indicates that the introduction of the alkali metal lithium in the I site is bene?cial for the production of large band gaps. This work will be helpful in exploring novel IR NLO materials with special structures and comprehensive properties in the chalcogenide system.
关键词： chalcogenides,infrared nonlinear optical materials,laser damage thresholds,cesium chloride topological structure,second-harmonic generation
更新于2025-09-19 17:13:59
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Effect of two-step post-treatment on optical properties, microstructure, and nanosecond laser damage threshold of HfO <sub/>2</sub> /TiO <sub/>2</sub> /SiO <sub/>2</sub> multilayer high reflection films
摘要： HfO2/TiO2/SiO2 periodic multilayer high reflection films deposited by an electron beam are post-treated by two-step post-treatment and thermal annealing post-treatment, respectively. The optical properties, microstructures, surface morphologies, and laser-induced damage threshold (LIDT) of the films are studied comparatively. The results show that the two-step post-treatment enhances the high reflection films’ density and reduces the film surface roughness and the defects of the film. The test results show that the LIDT of HfO2/TiO2/SiO2 high reflection films treated by two-step post-treatment reaches 32.8 J/cm2, which is 110.26% higher than that of the untreated film. Compared with the HfO2/TiO2/SiO2 high reflection films after thermal annealing post-treatment, the LIDT increased nearly 27.6% after two-step post-treatment. Two-step post-treatment of high reflection films can effectively remove the defects on the surface of the film, reduce the oxygen vacancies inside the film, and further increase the laser damage threshold of the high reflection films.
关键词： laser-induced damage threshold,HfO2/TiO2/SiO2,two-step post-treatment,thermal annealing,multilayer high reflection films
更新于2025-09-19 17:13:59
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Detection of forest road damage using mobile laser profilometry
摘要： In this study, we tested the ability of mobile laser pro?lometry to quantify and compare forest road surface damage. We scanned a 1044 m long road, composed of six sections built from base aggregate layers with top layers constructed from various materials: section stabilized with Portland cement, an aggregate road with the Tensar SS 30 Geogrid, milled asphalt, milled construction waste with lime cover, aggregate section, section covered with sand. We used vehicle-mounted Roadscanner device to measure the road pro?les while driving on the road, which took 170 s. The device recorded 4000 points per one pro?le perpendicular to the driving direction, with measuring frequency 1–5 kHz. The width of the road was 4 m (resolution 1 mm). Individual pro?les were connected into a 3D pro?le with the help of an integrated inertial system. On each road section, the system recorded the number of damages (potholes, cracks), volume of individual damages (dm3), area of individual damages (dm2), and the mean and maximal depth of the individual damages (cm). After the scanning, we measured the same road sections manually with resolution 10 mm, which took 8 h. The total damage volume was 9.75/27.61 m3 (scanning/manually), with a total area of 241.4/1277.8 m2. It represented 5.8/30.6% of the road surface (4176 m2). We found the road sections evaluated as the most damaged in case of manual measurements were di?erent than the most damaged sections evaluated by scanning. We found statistically signi?cant differences between individual road sections only in cases of the depths and volumes of recorded damages.
关键词： Laser pro?lometry,Road surface,Forest roads,Damage detection
更新于2025-09-19 17:13:59
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Nanosecond laser-induced surface damage and its mechanism of CaF2 optical window at 248a??nm KrF excimer laser
摘要： Calcium fluoride (CaF2) crystals is a kind of important optical material for ultraviolet (UV) and deep-ultraviolet (DUV) lithography and high-power laser-related applications. However, its laser-induced damage threshold (LIDT) directly affects the laser power, so that the above-mentioned applications could be limited. Therefore, the research on the damage characteristics and laser damage resistance of caf2 crystals is urgent. A 3D Finite-Difference Time-Domain (FDTD) method with Maxwell spinor equation is used, and the results show that the electric field intensity of rear surface is larger than that of front surface, which causes a lower threshold and is consistent with the experimental observations. And a thermo-mechanical coupled finite element model (FEM) of CaF2 with ce2o3 impurities, which are introduced by polishing process, has semiquantitatively described the damage mechanism of CaF2 by 248 nm-excimer laser.
关键词： laser-induced damage,FDTD,CaF2,FEM,ultraviolet excimer laser
更新于2025-09-19 17:13:59
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Crack monitoring in reinforced concrete beams by distributed optical fiber sensors
摘要： This paper investigates the use of distributed optical fiber sensors (DOFS) based on Optical Frequency Domain Reflectometry of Rayleigh backscattering for Structural Health Monitoring purposes in civil engineering structures. More specifically, the results of a series of laboratory experiments aimed at assessing the suitability and accuracy of DOFS for crack monitoring in reinforced concrete members subjected to external loading are reported. The experiments consisted on three-point bending tests of concrete beams, where a polyamide-coated optical fiber sensor was bonded directly onto the surface of an unaltered reinforcement bar and protected by a layer of silicone. The strain measurements obtained by the DOFS system exhibited an accuracy equivalent to that provided by traditional electrical foil gauges. Moreover, the analysis of the high spatial resolution strain profiles provided by the DOFS enabled the effective detection of crack formation. Furthermore, the comparison of the reinforcement strain profiles with measurements from a digital image correlation system revealed that determining the location of cracks and tracking the evolution of the crack width over time were both feasible, with most errors being below ±3 cm and ±20 mm, for the crack location and crack width, respectively.
关键词： crack monitoring,structural health monitoring,damage assessment,reinforced concrete,Concrete beams,distributed optical fiber sensors
更新于2025-09-19 17:13:59