Effect Of Laser Pulse Energy Research Articles

Effect of laser pulse energy on atomic lines and molecular bands in femtosecond LIBS of aluminum

This study explored the characteristics of atomic and molecular emissions in Al plasmas generated by femtosecond lasers. The influence of laser pulse energy on Al atoms and AlO molecules time-integrated spectra was examined. As laser pulse energy increased, the intensity of Al atoms increased, while the emission of AlO molecules first increased and then remained unchanged. Secondly, the vibration temperature of AlO was determined and found to result in strong emission at a low temperature. Finally, the influence of laser pulse energy on the time-resolved spectra of Al atom and AlO molecule was explored, finding consistency with the time-integrated emission. These results indicate that the Al atom and AlO molecule have different sensitivities to femtosecond laser pulse energy. This research enriches our knowledge of femtosecond laser-plasma interactions and has potential applications in material processing and spectroscopic analysis.

Quantitative laser-matter interaction: a 3D study of UV-fs-laser ablation on single crystalline Ru(0001).

Laser ablation is nowadays an extensively applied technology to probe the chemical composition of solid materials. It allows for precise targeting of micrometer objects on and in samples, and enables chemical depth profiling with nanometer resolution. An in-depth understanding of the 3D geometry of the ablation craters is crucial for precise calibration of the depth scale in chemical depth profiles. Herein we present a comprehensive study on laser ablation processes using a Gaussian-shaped UV-femtosecond irradiation source and present how the combination of three different imaging methods (scanning electron microscopy, interferometric microscopy, and X-ray computed tomography) can provide accurate information on the crater's shapes. Crater analysis by applying X-ray computed tomography is of considerable interest because it allows the imaging of an array of craters in one step with sub-µm accuracy and is not limited to the aspect ratio of the crater. X-ray computed tomography thereby complements the analysis of laser ablation craters. The study investigates the effect of laser pulse energy and laser burst count on a single crystal Ru(0001) sample. Single crystals ensure that there is no dependence on the grain orientations during the laser ablation process. An array of 156 craters of different dimensions ranging from <20 nm to ∼40 µm in depth were created. For each individually applied laser pulse, we measured the number of ions generated in the ablation plume with our laser ablation ionization mass spectrometer. We show to which extent the combination of these four techniques reveals valuable information on the ablation threshold, the ablation rate, and the limiting ablation depth. The latter is expected to be a consequence of decreasing irradiance upon increasing crater surface area. The ion signal generated was found to be proportional to the volume ablated up to the certain depth, which enables in-situ depth calibration during the measurement.

INFLUENCE OF LASER ENERGY ON CDS NANO PARTIALS PREPARED BY LASER INDUCED PLASMA

In this work ,cadmium sulfide (CdS) thin films deposited on glass substrates using Nd-YAG laser wavelength (1064 nm) laser-induced plasma deposition technique (PLD). The structural, morphology and optical properties of these films have been described as a change in the effect of laser pulse energy ( ). The X-ray diffraction results show that s all samples were polycrystalline hexagonal structure and the crystalline size ghange with increasing of the laser energy. The optical properties results show that the transmittance of all deposited thin films decreases with increasing of laser pulse energy .As a result of the microscopic examination of the surface, it was found that the surface is uniform and the granular size increases with the increase of the laser power.

Engineering Porosity in Electrospun Nanofiber Sheets by Laser Engraving: A Strategy to Fabricate 3D Scaffolds for Bone Graft Applications

Nanofiber features in a scaffold provide favorable niche for cellular attachment, proliferation, and differentiation propelling their interest in tissue engineering. However, the inability of seeded cells to infiltrate inside 3D structures of electrospun nanofibers has remained a persistent bottleneck for their greater applicability. In the present work, an approach to address this problem is presented. Macro-pores are designed in common graphic software created by a laser-engraving machine on electrospun nanofiber sheets composed of a bioinspired material-N-methylene phosphonic chitosan for facilitating cellular infiltration into 3D scaffold. Effect of laser pulse energy and pulse per inch on pore morphology are investigated and FTIR spectrum is examined to preclude the degradation of material due to laser-engraving process. Furthermore, the micro-fabricated nanofiber sheets with multi-scalar porosity are rolled up to form a 3D scaffold as graft through biomimetic approach for bone-tissue engineering applications. Culture of MG-63 cells on rolled up nanofiber sheets containing laser-engraved macro-porous 3D scaffolds demonstrated no cytotoxicity induced by the scaffolds from MTT assay, while cellular migration into the sheets was evident from scanning electron microscopy. It is concluded that combined micro-fabrication-rolling approach may be simple, rapid way to design 3D bone grafts based on 2D electrospun nanofiber sheet of natural/semi-synthetic polymers for better osteoconductivity.

The effect of laser pulse energy on ZnO nanoparticles formation by liquid phase pulsed laser ablation

Zinc Oxide nanoparticles were prepared using pulsed laser ablation process from a pure zinc metal placed inside a liquid environment. The latter is composed of acetyltrimethylammonium bromide (CTAB) of 10−3 molarity and distilled water. A Ti:Sapphire laser of 800 nm wavelength, 1 kHz pulse repetition rate, 130 fs pulse duration is used at three values of pulse energies of 0.05 mJ, 1.11 mJ and 1.15 mJ. The evaluation of the optical properties for the obtained suspension was applied through ultraviolet–visible absorption spectroscopy test (UV/VIS). The result showed peak wavelengths at 210 nm, 211 nm and 213 nm for the three used pulse energies 0.05 mJ, 1.11 mJ and 1.15 mJ respectively. This indicates a blue shift, which means smaller sizes of prepared nanoparticles, correlated with the decrease in laser energy. The blue shift in the absorption edge refers to the quantum confinement property for the produced nanoparticles. In addition, Fourier Transform Infrared Spectroscopy (FTIR) analysis was utilized to confirm zinc oxide nanoparticles formation represented by the absorption values at 435–445 cm−1. The shape and morphology of ZnO nanoparticles were characterized with scanning electron microscope (SEM).

VIS-NIR spectral and particles distribution of Au, Ag, Cu, Al and Ni nanoparticles synthesized in distilled water using laser ablation

In this research, gold (Au), silver (Ag), copper (Cu), aluminium (Al) and nickel (Ni) nanoparticles have been prepared by laser ablation in distilled water using Q-switched Nd: YAG. Comparative analysis between 1064 nm and 532 nm laser wavelength in term of absorption spectra and particle size distribution is performed. The synthesized nanoparticles were characterized by visible (VIS) and near infrared (NIR) spectrometer and transmission electron microscopy (TEM). The effect of laser pulse energy and laser wavelength on the size distribution and absorbance spectrum of metal nanoparticles was studied. The absorption peak intensities of the nanoparticles increase at higher laser pulse energy. It is discovered that for all metals, 532 nm laser produced nanoparticles with higher absorption peak intensities than 1064 nm. The work also shows that there is no noticeable difference in the size of the nanoparticles produced at 532 and 1064 nm for the Ni and Cu metals. However, a considerable size difference can be seen for Au, Ag, and Al at the two laser wavelengths. Smaller Ag nanoparticles were produced by 1064 nm laser while smaller Au and Al nanoparticles were produced by 532 nm laser.

Study on controllable surface morphology of the micro-pattern fabricated on metallic foil by laser shock imprinting

Laser shock imprinting was an advanced micro/nanostructure forming method, and had great potential application in Micro Electro Mechanical Systems (MEMS) and optoelectronic devices. However, the residual rough structure and micro defects on imprinted micro-pattern limited the industrial application of laser shock imprinting. In the study, the laser pre-shocked aluminum foil was introduced for fabricating ultrasmooth micro-pattern with high mechanical properties. The effect of laser pulse energy and overlap ratio on the micro-pattern imprinting was characterized by 3D morphology and deformation depth. The local morphology and nanoindentation of micro-pattern on different locations were also investigated to reveal robustness of roughness and mechanical properties. The experimental results indicated that the morphology and mechanical properties of micro-pattern on laser pre-shocked aluminum foil were greatly improved than that of on original aluminum foil. The laser pulse energy and overlap ratio had great influence on forming depth, and the morphology and mechanical properties of micro-pattern groove were better than that of the micro-pattern center. The hardness and roughness on micro-pattern groove were changed obviously (the hardness increased about 10% and the average roughness decreased to 4 nm). The laser pre-shock imprinting physics mechanism was evaluated by finite element modeling. The presented study demonstrated that appropriate laser shock imprinting parameter can realize to fabricate ultrasmooth, precise, controllable, and high mechanical properties micro-pattern on laser pre-shocked aluminum foil.

Parametric appraisal of mechanical and metallurgical behavior of butt welded joints using pulsed Nd:YAG laser on thin sheets of AISI 316

In the era of miniaturization, welding of thin sheets find wide spread applications in developing micro-scale products essentially used in bio-medical, aerospace and automobile industries. During welding of thin sheets, welding deformation needs to be addressed to obtain sound and strong joints. Experimental investigation has been made on laser butt welding using pulsed Nd:YAG laser. Specifically, the study attempts to examine the influence of laser parameters such as laser current, pulse width, and scanning speed on weld quality of thin sheets of 0.45 mm. The quality of weld beads have been analyzed by scanning electron microscope (SEM), optical microscope, and radiography and fractographic inspection. Further, mechanical characterization of the weld beads is made by estimating micro-hardness, residual stress, surface roughness, and welding strength. The study indicates that laser current is the most importance parameters in welding of thin sheets because it helps in obtaining good mechanical and metallurgical qualities of welded joints. The welding strength increases with increase in scanning speed to a certain level and then it reduces. Spot overlapping significantly influences on surface integrity (surface roughness) and welding strength of welded joints. Micro-hardness in fusion zone (FZ) is comparatively higher than that in the heat affected zone (HAZ) because of the difference in grain structure (coarseness) attributed to cooling rate. The study further indicates that there is significant effect of laser pulse energy on development of residual stresses in welded joints. The study is extended to develop empirical relationship between laser parameters and welding strength using non-linear regression analysis. The adequacy of the empirical model is checked by comparing the results obtained from empirical model and experimental values. A new meta-heuristic approach known as simple optimization (SOPT) algorithm has been adopted to obtain optimum parametric setting for welding strength. A relative error of 8.79% is obtained when welding strength at optimal parameter setting is compared with confirmatory experiment.

Experimental research on ultrasound-assisted underwater femtosecond laser drilling

AbstractIn order to diminish the occurrence of cavitation bubbles during the liquid-assisted laser machining, ultrasound-assisted underwater femtosecond laser drilling on stainless steel is adopted. This method greatly diminishes the optical disturbance of cavitation bubbles. By investigating and analyzing the effect of laser pulse energy and pulse number on the morphology of the holes, it has been found that ultrasound not only has a remarkable function of forming a hole with clean and flat bottom, but also reduces debris redeposition around the processing area. This method improves the machining quality. Besides, it also improves the depth-to-diameter ratio of the hole about 20%.

Effect of Laser Fluence on Magnetic Properties of Thin MnxSi1 – x (x ≈ 0.5) Films Prepared by Pulsed Laser Deposition

Abstract—The effect of laser pulse energy E on the possibility of forming of a homogeneous “high-temperature” ferromagnetic phase in MnxSi1 – x (x ≈ 0.5) alloy films grown by pulsed laser deposition onto an Al2O3 (0001) substrate has been studied. The high-temperature phase with manganese concentration x ≈ 0.53 and the Curie temperature TC ~ 200–300 K is shown to form near the substrate at the initial stage of the film growth. In this case, high values E ≥ 6.8 J/cm2 favor the stabilization of this phase over all film thickness, while low values E = 2.6–5.7 J/cm2 lead to a decrease in the manganese concentration in the upper film layer and the formation of additional “low–temperature” phase with TC ≈ 30–50 K provided by silicides MnSi and Mn4Si7 crystallites.

Effect of Laser Pulse Energy on the Structure, Morphology and Optical Properties of Tantalum-Oxide Nanoparticles Generated by Laser Ablation

Effect of Laser Pulse Energy on the Structure, Morphology and Optical Properties of Tantalum-Oxide Nanoparticles Generated by Laser Ablation

The research of micro pattern transferring on metallic foil via micro-energy ultraviolet pulse laser shock

A micro-energy high frequency ultraviolet pulse laser was introduced for fabricating the micro pattern on pure aluminum foil by laser shock transferring. The copper mesh mold (mesh size: 400# and 1000#) and pure aluminum foil were used to investigate the effect of laser pulse energy and overlap ratio on micro pattern transferring. A FEM model was adopted to simulate the aluminum foil deformation and plastic strain in laser shock process. To investigate the micro forming mechanism of laser shock transferring, the micro morphology of significant area on processed micro pattern was observed by atomic force microscope (AFM). The experimental results revealed that the depth of transferred micro pattern increased with the increasing of single pulse energy and overlap ratio within certain range. The forming depth of aluminum foil imprinted from 400# mold was larger than that of 1000#, and more sensitive to pulse energy and overlap ratio. The aluminum foil on mold bars was smoother than that of on mold holes. The study demonstrated that the micro-energy ultraviolet pulse laser shock can realize the precise, controllable, fast and ultrahigh strain rate fabrication of surface microstructure.

Improving the Cell Viability and Isolating Precision of Laser-induced Forward Transfer Process by Maintaining a Proper Environment with a Microchip.

Aiming to improve the laser-induced forward transfer (LIFT) cell isolation process, a polydimethylsiloxane (PDMS) layer with micro-hole arrays was employed to improve the cell separation precision, and a microchip with heater was developed to maintain the working area at 100% humidity and 37°C with the purpose to preserve the viability of the isolated cells. A series of experiments were conducted to verify the contributions of the optimization to LIFT cell isolation process as well as to study the effect of laser pulse energy, laser spot size and the titanium thickness on cell isolation. With 40µm laser spot size and 40nm thick of titanium, laser energy threshold for 100% single cell isolating succeed ratio is 7µJ. According to the staining images and proliferation ratios, the chip did help to improve the cell availability and the cells can recover from the juries at least a day earlier comparing to the samples processed without the chip. With a Lattice Boltzmann model, the cell isolation process is numerically studied and it turns out that the micro-hole makes the isolation process shift to a micro-syringe injection model leading to the lower laser energy threshold for cell separation and fewer injuries.

Влияние плотности энергии лазерного пучка на магнитные свойства тонких пленок Mn-=SUB=-x-=/SUB=-Si-=SUB=-1-x-=/SUB=- (x&amp;#126;0.5), приготовленных методом импульсного лазерного осаждения

Abstract —The effect of laser pulse energy E on the possibility of forming of a homogeneous “high-temperature” ferromagnetic phase in Mn_ x Si_1 – _ x ( x ≈ 0.5) alloy films grown by pulsed laser deposition onto an Al_2O_3 (0001) substrate has been studied. The high-temperature phase with manganese concentration x ≈ 0.53 and the Curie temperature T _C ~ 200–300 K is shown to form near the substrate at the initial stage of the film growth. In this case, high values E ≥ 6.8 J/cm^2 favor the stabilization of this phase over all film thickness, while low values E = 2.6–5.7 J/cm^2 lead to a decrease in the manganese concentration in the upper film layer and the formation of additional “low–temperature” phase with T _C ≈ 30–50 K provided by silicides MnSi and Mn_4Si_7 crystallites.

Effect of Laser Pulse Energy on the Characteristics of Au Nanoparticles and Applications in medicine

In this paper, Au NPs prepared by pulsed laser ablation in liquid (PLAL) with different laser energy (200, 360,500,660 and 800 m J) with number of pulses (1000pulse), at wavelength 1064 nm, and repetition rate of 1Hz. The structural, morphological and optical properties were discussed. XRD spectra showed the diffraction peak. AFM showed the average diameter. The optical properties showed increase absorption spectra at increase energy. Further in vitro antibacterial activities of Au NPs were investigated against Gram positive and Gram negative. Staphylococcus aureus and E.Coli. Studied Toxicity of the synthesized Au NPs on human blood cells.

A comparative study on laser induced shock cleaning of radioactive contaminants in air and water

Efficient removal of Uranium-di-oxide (UO2) particulates from stainless steel surface was effected by Nd-YAG laser induced plasma shock waves in air as well as in water environment. The propagation velocity of the generated shock wave was measured by employing the photo-acoustic probe deflection method. Monitoring of the alpha activity of the sample with a ZnS (Ag) scintillation detector before and after the laser exposure allowed the estimation of decontamination efficiency defined as the percentage removal of the initial activity. Experiments were carried out to study the effect of laser pulse energy, number of laser exposures, orientation of the sample, the separation between the substrate surface and the onset point of the shock wave on the de-contamination efficiency. The most optimised cleaning was found to occur when the laser beam impinged normally on the sample that was immersed in water and placed at a distance of ∼0.7 mm from the laser focal spot. Analysis of the cleaned surface by optical microscopes established that laser induced shock cleaning in no way altered the surface property. The shock force generated in both air and water has been estimated theoretically and has been found to exceed the Van der Waal’s binding force for spherical contaminant particulate.

Measurement of Eu and Yb in aqueous solutions by underwater laser induced breakdown spectroscopy

In this paper, we report the use of laser induced breakdown spectroscopy (LIBS) to detect dissolved Eu and Yb in bulk aqueous solutions. Ten strong emission lines of Eu and one strong emission line of Yb were identified in the underwater LIBS spectra obtained by using Czerny–Turner spectrometer within the wavelength range of 375–515nm. Temporal evolution of plasma and the effect of laser pulse energy on the spectral emission were studied. Calibration curves using the concentration range from 500 to 10,000ppm were developed and limits of detection for Eu and Yb were estimated to be 209 and 156ppm, respectively.

Structural and morphological characterization of ternary nanocrystalline Cu-In-S thin films prepared by laser ablation

Thin nanocrystalline Cu-In-S films are prepared by pulsed laser ablation in vacuum with Nd:YAG laser operating at 1064 nm on Si (100) substrates. As a target, a CuInS2 quantum dots powder, synthesized by sonochemical template-free colloidal approach and pressed to form a pellet is used. The structure and morphology of the deposited films were studied employing X-ray diffraction, scanning electron microscopy, and atomic force microscopy techniques. The analysis of the deposited thin films revealed predominant cubic Cu1.7In0.05S phase. It has been found that deposited films were nanocrystalline. The effect of laser pulse energy and deposition time on the structure and morphology of as-prepared films is studied. Slight mean diameter increase from 8 nm to 13 nm with deposition time and applied power was observed, as the time dependence is more pronounced. On the contrary, six fold increase from 7.4 to 44.3 nm of the surface root mean square roughness was estimated with augmentation of the applied laser pulse energy.

Comparative Study of Two Methods of Orthogonal Double-Pulse Laser-Induced Breakdown Spectroscopy of Aluminum

Double-pulse laser induced breakdown spectroscopy (DP-LIBS) of aluminum sample is studied experimentally in orthogonal configuration in air. In this configuration, two schemes of reheating and pre-ablation are examined and the results are compared with single pulse one. The effect of delay time between two laser pulses on emission line intensities of plasma is investigated. Some of the parameters that have been involved in different mechanism of signal enhancement such as plasma temperature, sample heating effects, atmospheric effects, and modification of the ablation dynamics are more discussed. Investigation of the effect of laser pulse energy on emission line intensities in single pulse LIBS experiment demonstrate that because of saturation effects the intensities will not increase necessarily by increasing the laser pulse energy. Moreover, the results show that the electron temperature and rate of mass removal in orthogonal configuration of DP-LIBS is higher than that of single pulse with the same total energy. It is suggested that for correct comparison between single and double pulse results, the optimum pulse energy in single pulse should be considered. Overall, our results demonstrate that under optimized conditions the signal enhancement is much more in pre-ablation configuration than re-heating configuration.

Liquid-assisted Pulsed Laser Ablation Synthesized Titanium Ferrite Nanoparticles: Structural, Optical And Magnetic Properties

Titanium ferrite nanoparticles (NPs) with controlled titanium to iron ratios (Ti/Fe) were synthesized using liquid-assisted pulsed laser ablation (LA-PLA) technique. Present manuscript describes effect of variation of Ti/Fe ratio in the target and the effect of laser pulse energy on size, shape, optical band gap, crystalline phase and magnetic properties of as-synthesized titanium ferrite NPs. UV-visible absorption, TEM and XRD investigations reveal that size of as-produced NPs decreases with the increase of Ti in the Ti/Fe targets used for ablation. Variation in laser pulse energy at a given Ti/Fe ratio has lesser dependence on size, shape and magnetic properties of produced NPs. Higher ferromagnetism with larger sized particles demonstrates dominance of bulk phenomenon over surface defects for the generation of ferromagnetic responsible spins. As-produced titanium ferrite nanomaterials may be used as promising magnetic recovery catalysts (MRCs).