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Atomic simulation of irradiation of Cu film using femtosecond laser with different pulse durations
摘要： It is necessary to understand the light-matter interaction for application of femtosecond laser micro/nanoprocessing. In this work, the authors investigated the melting and disintegration behavior of a Cu film irradiated by a femtosecond laser with different pulse durations in the range of 35–500 fs by using a combined two temperature model (TTM) and molecular dynamics (MD) method. On the basis of TTM-MD, the temperature and stress evolution of the Cu film were analyzed. The result indicated that the Cu film disintegrates when the pulse duration is shorter than 100 fs but melts at a pulse duration of 200 fs. The photomechanical and thermomechanical evolutions induced by the femtosecond laser were also analyzed. The stress wave and increasing temperature were the main reasons for film disintegration and vibration. The snapshots of the Cu film indicate the melting and disintegration processes on an atomic scale. It shows that the melting occurs homogeneously, whereas the disintegration occurs at the center of the film. These results are helpful to understand the mechanism of femtosecond laser materials ablation.
关键词： TTM-MD simulation,Cu film,pulse durations,femtosecond laser,irradiation
更新于2025-09-23 15:21:01
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Laser-Induced Optoelectronic and Crystallographic Tuning of Methyl Ammonium Iodobismuthate Perovskite for Improved Performance of Sandwiched a?? Type Photodetectors
摘要： Towards development of high-performance perovskite based photodetectors, it is required that optical and crystallographic properties of perovskites materials be enhanced through perovskites materials modification. Many attempts on this quest result in alteration of chemical structure of perovskites materials through introduction of dopants. Here in, we present a clean and structural preservative technique of tuning optical and crystallographic properties of bismuth based lead free perovskite materials through irradiation with 2.5 mJ laser pulses ejected from Nd:YAG LASER operating in its second harmonics. XRD spectra show improved crystallinity and reduced crystallite size, SEM images show defect – minimized surface morphology, PL spectra show minimized rate of Auger recombination and absorbance spectra show improved absorbance at a constant band gap value. Consequently, simplified sandwiched architectural type photodetectors fabricated with the modified bismuth based perovskite materials display maximum photodetectivity of 4.5 × 109 Jones, maximum photoresponsivity of 25 μA/W, maximum photosensitivity of about 104 and minimum optical switching times of 10 ms under testing conditions of -2 V bias voltage, 15 mW/cm2 incident solar light and room temperature. Thus, laser pulses irradiation presents an alternative method of enhancing optical and crystallographic properties of perovskite materials from which highly efficient classes of photonics and photovoltaic devices can be developed.
关键词： Laser Irradiation,crystallographic properties,optical properties,perovskite photodetectors,lead free perovskites materials
更新于2025-09-23 15:21:01
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Kinetics of molecular decomposition under irradiation of gold nanoparticles with nanosecond laser pulsesa??A 5-Bromouracil case study
摘要： Laser illuminated gold nanoparticles (AuNPs) efficiently absorb light and heat up the surrounding medium, leading to versatile applications ranging from plasmonic catalysis to cancer photothermal therapy. Therefore, an in-depth understanding of the thermal, optical, and electron induced reaction pathways is required. Here, the electrophilic DNA nucleobase analog 5-Bromouracil (BrU) has been used as a model compound to study its decomposition in the vicinity of AuNPs illuminated with intense ns laser pulses under various conditions. The plasmonic response of the AuNPs and the concentration of BrU and resulting photoproducts have been tracked by ultraviolet and visible (UV–Vis) spectroscopy as a function of the irradiation time. A kinetic model has been developed to determine the reaction rates of two parallel fragmentation pathways of BrU, and their dependency on laser fluence and adsorption on the AuNP have been evaluated. In addition, the size and the electric field enhancement of the decomposed AuNPs have been determined by atomic force microscopy and finite domain time difference calculations, respectively. A minor influence of the direct photoreaction and a strong effect of the heating of the AuNPs have been revealed. However, due to the size reduction of the irradiated AuNPs, a trade-off between laser fluence and plasmonic response of the AuNPs has been observed. Hence, the decomposition of the AuNPs might be limiting the achievable temperatures under irradiation with several laser pulses. These findings need to be considered for an efficient design of catalytic plasmonic systems.
关键词： gold nanoparticles,plasmonic catalysis,5-Bromouracil,laser irradiation,photothermal therapy
更新于2025-09-23 15:21:01
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Optical phase change in bismuth through structural distortions induced by laser irradiation
摘要： Semimetal bismuth (Bi) is known to possess a wide range of peculiar properties, owing to its unique electronic band structure. Its electronic band can easily be distorted by structural changes, and thereby undergo transitions between semimetal to either semiconductor or metal states. Utilising a focused laser beam, one can easily introduce structural defects, along with phase changes, oxidation, and morphological modifications. Confocal Raman microscopy indicated that the as-fabricated Bi droplets inhibit the Raman signal from the underlying silicon (Si) substrate. After a laser flash heating step, the intensity of Si optical phonons was strongly enhanced at the positions of Bi droplets, and exceeding the intensity from the bare Si substrate. Thus, such laser irradiating step on the Bi droplets induces an optical phase change. The optical phase change was detected as going from inhibition to strong enhancement of the underlying Si substrate Raman signal. From the observed Bi optical phonon modes (Eg and A1g), alterations in the Raman peaks due to laser exposure indicated that the ordered crystallinity in pristine Bi droplets became deteriorated. The effects of atomic displacements and loss of structural order in Bi droplets impacts its dielectric response. The observed Si Raman signal enhancement is similar to the surface-enhanced Raman scattering effect typically known for noble metals.
关键词： phase change,Bismuth,structural defects,laser irradiation,Raman spectroscopy
更新于2025-09-23 15:21:01
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[Ceramic Engineering and Science Proceedings] Proceeding of the 42nd International Conference on Advanced Ceramics and Composites (Ceramic Engineering and Science Proceedings Volume 39, Issue 2) || Influences of Laser Condition and Slit Shape on Joinability of Zircaloy-SiC/SiC Composite Tube Joint
摘要： As for the fuel cladding in the light-water reactor, silicon carbide fiber reinforced silicon carbide composite (SiC/SiC composite) is one of the promising candidates as a replacement of zircaloy due to many superiorities, where it is necessary to develop the end-cap seal of SiC/SiC composite cladding. In this research, the caulking method was employed as the method for sealing the end cap of SiC/SiC composite tube by zircaloy tube where the titanium micro-powder was inserted between two tubes. The diode or fiber laser was circumferentially irradiated on the outer surface of zircaloy tube, and the insert method of titanium powder was varied by changing the cutting method of SiC/SiC composite tube. The results using the diode laser irradiations with the screw cutting indicated that the wider width of irradiation line seems to be inadequate because the shrinkage of zircaloy would break the thread of SiC/SiC composite. In addition, the examinations about the slit shape effect for the flat cutting suggested that the hook slit is considered to be the best cutting method for holding the titanium powder during the laser irradiation where the width of slit should be narrower than that of laser irradiation line.
关键词： SiC/SiC composite,titanium micro-powder,caulking method,laser irradiation,zircaloy
更新于2025-09-23 15:21:01
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Optical properties of poly (ethyl methacrylate) - cellulose acetate propionate blend film irradiated with Nd:YAG laser
摘要： Poly (ethyl methacrylate) (PEMA) - cellulose acetate propionate (CAP) blend film was prepared using the cast technique. A Q-switched Nd: YAG laser beam with a wavelength of 266 nm, a pulse duration of 10-ns, a repetition rate10 Hz and 0.018 J/cm2 fluence was used to irradiate the prepared film. The optical absorption of pristine and irradiated sample was studied within 200–500 nm wavelength region. The absorbance increases with laser irradiation time over the full wavelength region which is attributed to an increase of the crosslinking network. Examining Tauc plots revealed a transition of the direct allowed type with optical energy gap value of 4.92 eV for the pristine blend film which has decreased to 4.30 eV after laser irradiation for 90 min. The refractive index, finesse coefficient, dielectric function, Brewster, and critical angles demonstrated dispersion in the 200–500 nm wavelength range.
关键词： PEMA,CAP,Band gap,UV laser irradiation
更新于2025-09-23 15:21:01
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Tunable thermo-piezo-plasmonic effect on core/shell nanoparticles under laser irradiation and external electric field
摘要： This work is focused on the characterization of the opto-heating generation in thermo-piezo-plasmonic solutions of gold-PbZrTiO3 (PZT) core/shell nanoparticles. Core/shell nanoparticles have been prepared by the laser ablation in liquid method. Linear and nonlinear optical properties of proposed nanoparticles were studied by optical spectroscopy and the Z-scan technique under external voltage to investigate the piezo-photonic effect. Furthermore, the linear optical properties of these nanostructures were calculated vie dipole approximation method with different core size and different shell thickness of samples immersed in water and poly-vinyl-pyrrolidone. In addition, thermo-plasmonic effects of samples are investigated theoretically and experimentally by the finite element method of COMSOL multiphysics V5.4 and infrared camera under laser irradiation and external electric field. The results revealed a clear tunable and adjustable linear and nonlinear behavior and thermo-piezo-plasmonic properties under external effects. The temperature elevation is ranging of ?T = 3.7–14.1 °C under different external effects. Accordingly, these results encourage to uses proposed samples for the cancer treatment and the different biomedical applications.
关键词： Nonlinear refractive index,External electric field,Core/shell NPs,Laser irradiation,Thermoplasmonic,Piezoelectric,Z-scan technique,Schottky barrier
更新于2025-09-23 15:21:01
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Topographic characterization of zirconia-based ceramics by atomic force microscopy: A case study on different laser irradiations
摘要： The purpose of the present study is to evaluate the effects of different laser irradiations including Nd-YAG (neodymium-doped yttrium aluminum garnet laser; Nd:Y3Al5O12), Er-YAG (erbium-doped yttrium aluminum garnet laser, erbium YAG laser), and Carbon dioxide (CO2) infrared lasers on surface topography of zirconia-based ceramics samples which were prepared by copy milling technique. Three dimensional (3D) atomic force microscopy (AFM) images were applied to investigate surface properties by extracting information via MountainsMap? Premium software which divides the surface into peaks and pits and through watershed segmentation algorithm. This method made motif analysis possible by detecting surface dimensions, curvature, volume, perimeters, shape, structure, etc.
关键词： Atomic force microscopy,Laser irradiation,Stereometric analysis,Fractal analysis
更新于2025-09-23 15:21:01
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Thermal coagulum formation and hemostasis during repeated multipulse Nd:YAG laser treatment of cutaneous vascular lesions: animal experiment study
摘要： Laser therapy has been widely used to treat port-wine stain (PWS) and other cutaneous vascular lesions via selective photothermolysis. High incident laser fluence is always prohibited in clinic to prevent the thermal damage in normal skin tissue, leading to insufficient energy deposition on the target blood vessel and incomplete clearance of PWS lesion. In this study, repeated multipulse laser (RMPL) irradiation was proposed to induce acute thermal damage to target blood vessels with low incident fluence (40 J/cm2 for 1064-nm Nd:YAG laser). The feasibility of the method was investigated using animal models. Repeated multipulse irradiation cycles with 10-min intervals were performed in RMPL. A hamster dorsal skin chamber model with a visualization system was constructed to investigate the instant generation of thermal coagulum and relevant hemostasis by thrombus formation during and after irradiation under 1064 nm Nd:YAG single multipulse laser (SMPL) and RMPL irradiation. The diameter of the target blood vessel and the size of thermal coagula were measured before and after laser irradiation. The reflectance spectra of the dorsal skin were measured by a reflectance spectrometer during RMPL. Stasis thermal coagula that clogged the vessel lumen were generated during SMPL irradiation with low incident fluence. However, there was no acute thermal damage of blood vessels. Reflectance spectra measurement showed that the generation of thermal coagula and subsequent thrombus formation increases blood absorption by more than 10% within the first 10 min after laser irradiation. Acute vessel thermal damage could be induced in the target blood vessel by RMPL with low incident fluence of 40 J/cm2. Compared with our previous SMPL study, nearly 30% reduction in incident laser fluence was achieved by RMPL. Low fluence RMPL may be a promising approach to improve the therapeutic outcome for patients with cutaneous vascular lesions by improving energy deposition on the target blood vessel.
关键词： Thermal coagula,1064-nm Nd:YAG laser,Port-wine stain,Repeated multiple pulse laser irradiation,Thrombus formation
更新于2025-09-23 15:19:57
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Facile fabrication of multi-scale microgroove textures on Ti-based surface by coupling the re-solidification bulges derived from nanosecond laser irradiation
摘要： A facile method is proposed to fabricate multi-scale microgroove textures (MGT) on Ti-based implant material. The effect of some primary parameters on the morphology of laser-irradiated surface is studied in detail. The results show that at the scanning speed of 42 mm/s, when the laser intensity is ≥4.0 J/cm2 typical microgroove structure with raised edges is produced by single-line scanning irradiation, and various MGT can be easily fabricated by multi-line scanning irradiation through properly adjusting the scanning interval in accordance with the feature size of microgroove structures. Meanwhile, it is firstly found that multi-scale MGT perpendicular to the scanning direction can be achieved by applying suitable high scanning speed with small scanning interval. Using a laser spot with the diameter of 20 μm, multi-scale MGT with various periods ranging from 15 (less than the laser spot diameter) to 35 μm are successfully fabricated on TA2 surfaces, and perpendicular ones with the same period of 21 μm but different ridge widths are also obtained. The aspect ratio of these MGT is > 1.5. Wettability measurements reveal that the water droplet on the produced multi-scale MGT owns anisotropic spreading speeds or spreading lengths. The energy dispersive spectroscopy tests indicate that their ridges are rich in titanium oxides which are good hemo-compatibility materials. The proposed method has a promising application for fabricating multi-scale MGT like those on natural vessel to the stent surface to improve its hemo-compatibility.
关键词： Microtexture,Functional surface,Anisotropic wettability,Laser irradiation,Microgroove
更新于2025-09-23 15:19:57