Influence Of Laser Pulse Energy Research Articles

Oblique incidence of ultrafast laser for glass butt welding.

Lap welding restricts the connection state of glasses by vertically incident ultrafast laser at the interface to be welded, which cannot meet the increasingly flexible welding needs. In this Letter, glass butt welding is achieved by oblique incidence of an ultrafast laser, expanding the applicability of ultrafast laser glass welding. Furthermore, the propagation path of the laser beam after oblique incidence into a glass is solved based on geometric optics, the dynamic development of the molten pool in a glass is observed through a high-speed camera, and the mechanism of glass butt welding is elucidated. Finally, the influence of laser pulse energy, glass tilt angle, and defocus amount on welding strength is investigated, achieving a maximum shear strength of 11.5 MPa.

Numerical Simulation and Experimental Investigation of ps Pulsed Laser Modification inside 4H-SiC Material

Silicon Carbide (SiC) is the predominant substrate material for optoelectronic-integrated devices. However, it challenges the wafer-slicing process because of its high hardness, brittleness, and other material characteristics. Laser processing has gained prominence as the primary method, leveraging its merits of high efficiency, precision, and micro-destructiveness. In this study, a finite element method is applied to calculate the temperature field distribution resulting from the electric field of a Gaussian beam. The simulation considers laser propagation inside 4H-SiC, non-linear absorption, and spherical aberration induced by the refractive index of the material. The influence of laser pulse energy and focusing depth are considered. The results indicate that the modification depths decrease with the increasing focusing depth. With the increase of laser pulse energy, the depth of the modification layer increases continuously. Moreover, an experimental setup has been devised to furnish valuable references in validating the proposed model.

Optical Properties of Germanium Nanoparticles Prepared by Laser Ablation

The synthesis of germanium nanoparticles (Ge NPs) through pulsed laser ablation in deionized water is investigated for Nanophotonics and optoelectronic applications. This study delves into the influence of laser pulse energy on Ge NP properties, specifically highlighting size control and optical characteristics. Our findings reveal a significant reduction in Ge NP size, from an initial 30 nm to 20 nm, as the laser pulse energy increases. Notably, we observed size-dependent blue luminescence from the synthesized Ge NPs. This controlled synthesis holds promise for optoelectronics and sensing applications. The study provides valuable insights into precise Ge NP synthesis and underscores their intriguing optical properties, paving the way for advanced Nanophotonic devices.

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.

Testing the Influence of Laser Pulse Energy and Rate in the Atom Probe Tomography Analysis of Minerals.

The use of atom probe tomography (APT) for mineral analysis is contributing to fundamental studies in Earth Sciences. Meanwhile, the need for standardization of this technique is becoming evident. Pending the use of mineral standards, the optimization of analysis parameters is needed to facilitate the study of different mineral groups in terms of data collection and quality. The laser pulse rate and energy are variables that highly affect the atom evaporation process occurring during APT analysis, and their testing is important to forecast mineral behavior and obtain the best possible data. In this study, five minerals representative of major groups (albite, As-pyrite, barite, olivine, and monazite) were analyzed over a range of laser pulse energies (10-50 pJ) and rates (100-250 kHz) to assess output parameter quality and evaluate compositional estimate stoichiometry. Among the studied minerals, As-pyrite, with the higher thermal conductivity and lower band gap, was the most affected by the laser pulse variation. Chemical composition estimates equal or close to the general chemical formula were achieved for monazite and As-pyrite. The analysis of multihit events has proved to be the best strategy to verify the efficacy of the evaporation process and to evaluate the best laser pulse setting for minerals.

Process exploration of β-Ga2O3 blind hole processing by water-assisted femtosecond laser technology

β-Ga2O3 is a promising high-performance material with broad application prospects in the micro-electro-mechanical-systems (MEMSs). It can be used in extreme environments such as ultralow temperatures and intense radiation, but its hardness, brittleness, and easy cleavage are the primary defect in processing. As a substrate material for the next generation of large-scale integrated circuits, blind hole processing of β-Ga2O3 has attracted intense attention. In this work, we investigated the blind hole on (010) β-Ga2O3 surfaces treated with a femtosecond-pulse laser at the wavelength of 1030 nm and the pulse width of 285 fs. Water-assisted fs laser micromachining is proposed to solve the deposition of pore debris within the hole in the air environment. Furthermore, the influence of laser pulse energy, laser pulse numbers, liquid layer thickness, and laser repetition rate on the surface morphology of the blind hole was studied by using the control variable method. The results show that precise processing of β-Ga2O3 blind holes can be achieved by controlling fs laser processing parameters. In this work, the proposed liquid-assisted fs laser machining was proved to be a reliable tool for performing high-quality β-Ga2O3 blind hole processing, which has important implications for device applications of β-Ga2O3 substrates.

Influence of Laser Pulse Energy on CFTS Thin Film Deposited by Pulsed Laser Deposition

Influence of Laser Pulse Energy on CFTS Thin Film Deposited by Pulsed Laser Deposition

Influence of Laser Pulse Energy on The Electrical Properties of Cu2O Nanoparticles Prepared by Laser Induce Plasma

In this work, copper oxide films (Cu2O) were grown using laser ablation from Nd:YAG laser with a wavelength of 1064 nm in vacuum. Electrical properties of the nanoparticles were investigated as a function of the laser pulse energies, including (600-900) mJ and annealing temperature was varied at (473,573 and 673)k. Hall Effect measurement was used to determine the electrical mobility, carrier concentration, conductivity and majority of electrical carriers.

Complex evaporation behavior of a transition metal carbo-nitride (Hf(C,N)) studied by atom probe tomography

The use of pulsed lasers in atom probe tomography has enabled the analysis of lower conductivity materials such as hafnium carbo-nitrides. The variability of experimental parameters can have a profound effect on field evaporation behavior, data quality and compositional accuracy. This is especially challenging for materials such as hafnium carbo-nitride, where a mixture of covalent, ionic and metallic bonding types is present. Here we study the influence of laser pulse energy on how the field evaporation evolves in a hafnium carbo-nitride and how that impacts data quality and compositional accuracy. Changing the laser pulse energy, while keeping other parameters constant, alters the resulting composition. A gain in Hf concentration is observed for higher laser pulse energies while at the same time the N concentration decreases. At lower laser pulse energies, the obtained composition is in good agreement with the reference bulk composition of the material. Furthermore, our results demonstrate that assessing the quality of an APT experiment or dataset merely based on commonly used metrics such as quality of mass spectrum, hit distribution on the detector, hit multiplicity and mass resolving power, can be misleading and is not enough to ensure the most accurate compositional data. Moreover, it is shown that the complex evaporation behavior of transition metal carbo-nitrides and potential ion loss mechanisms are not well enough understood yet and further work is required to fully comprehend these complex behaviors in these types of ceramics.

Laser Indirect Shock Welding of Fine Wire to Metal Sheet.

The purpose of this paper is to present an advanced method for welding fine wire to metal sheet, namely laser indirect shock welding (LISW). This process uses silica gel as driver sheet to accelerate the metal sheet toward the wire to obtain metallurgical bonding. A series of experiments were implemented to validate the welding ability of Al sheet/Cu wire and Al sheet/Ag wire. It was found that the use of a driver sheet can maintain high surface quality of the metal sheet. With the increase of laser pulse energy, the bonding area of the sheet/wire increased and the welding interfaces were nearly flat. Energy dispersive spectroscopy (EDS) results show that the intermetallic phases were absent and a short element diffusion layer which would limit the formation of the intermetallic phases emerging at the welding interface. A tensile shear test was used to measure the mechanical strength of the welding joints. The influence of laser pulse energy on the tensile failure modes was investigated, and two failure modes, including interfacial failure and failure through the wire, were observed. The nanoindentation test results indicate that as the distance to the welding interface decreased, the microhardness increased due to the plastic deformation becoming more violent.

Optimization of femtosecond laser cutting of biodegradable polymer for medical devices manufacturing

This paper describes the experimental parameters involved in the femtosecond laser micromachining of biodegradable poly(L-lactide) which is frequently used in biomedical applications such as vascular stents or scaffolds. We investigated the influence of laser pulse energy, scanning strategy and number of overscans on the laser cutting throughput. The process parameters that enable reducing of a heat affected zone were determined. As a result, the optimal scanning strategy was determined in order to obtain high aspect ratio trenches in 380 ?m thick biodegradable polymer sheet. Full Text: PDF ReferencesW. Jia et al. "Effects of high-repetition-rate femtosecond laser micromachining on the physical and chemical properties of polylactide (PLA)", Opt. Express 23, 21 (2015). CrossRef F. Hendricks, R. Patel, and V.V. Matylistsky, "Micromachining of bio-absorbable stents with ultra-short pulse lasers", Proc. SPIE 9355, 935502 (2015). CrossRef W.Y. Yeong et al. "Annealing of Biodegradable Polymer Induced by Femtosecond Laser Micromachining", Adv. Eng. Mater. 4, 12 (2010). CrossRef K. Stolberg et al. "IR and green femtosecond laser machining of heat sensitive materials for medical devices at micrometer scale", Proc. SPIE 8968, 89680E (2014). CrossRef F. Hendricks et al. "High aspect ratio microstructuring of transparent dielectrics using femtosecond laser pulses: method for optimization of the machining throughput", Appl. Phys. A 117, 1 (2014). CrossRef A. Antonczak et al. "Degradation of poly(l-lactide) under CO2 laser treatment above the ablation threshold", Polym. Deg. Stab. 109, 97-105 (2014) CrossRef B. Stepak et al. "The influence of ArF excimer laser micromachining on physicochemical properties of bioresorbable poly(L-lactide)", Proc SPIE 9736, 97361T (2016). CrossRef

Influence of laser pulse energy on the microstructure and optical properties of Cu2ZnSnS4 films by one-step pulsed laser deposition

Polycrystalline Cu2ZnSnS4 (CZTS) films were deposited on ITO conductive glass substrates by one-step pulsed laser deposition. The influence of laser pulse energy on the microstructure and optical properties was investigated. The results indicate that all the films are rich in Sn, poor in S and well crystallized with dominant (112) preferred orientation. At laser pulse energies of 130, 165 and 180mJ, SnS2 impurity phase exists in CZTS films, which is probably the reason for their larger bandgaps (1.61–1.67eV) compared with that of a stoichiometric CZTS film (around 1.50eV). While at the laser pulse energy of 150mJ, an attractive Cu-poor and Zn-rich, large grain size and single-phase CZTS film can be obtained. In such a film, excess Cu vacancies reduce the valence band maximum (VBM) of CZTS, leading to the blue shift of its bandgap (1.60eV).

Laser-induced fusion of human embryonic stem cells with optical tweezers

We report a study on the laser-induced fusion of human embryonic stem cells (hESCs) at the single-cell level. Cells were manipulated by optical tweezers and fused under irradiation with pulsed UV laser at 355 nm. Successful fusion was indicated by green fluorescence protein transfer. The influence of laser pulse energy on the fusion efficiency was investigated. The fused products were viable as gauged by live cell staining. Successful fusion of hESCs with somatic cells was also demonstrated. The reported fusion outcome may facilitate studies of cell differentiation, maturation, and reprogramming.

Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel

A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected.

Liquids microprinting through a novel film-free femtosecond laser based technique

Laser-induced forward transfer (LIFT) is a high resolution microprinting technique in which small amounts of material are transferred from a previously prepared donor thin film to a receptor substrate. The application of LIFT to liquid donor films allows depositing complex and fragile materials in solution or suspension without compromising the integrity of the deposited material. However, the main drawback of LIFT is the preparation of the donor material in thin film form, being difficult to obtain reproducible thin films with thickness uniformity and good stability. In this work we present a laser microprinting technique that is able to overcome the drawbacks associated with the preparation of the liquid film, allowing the deposition of well-defined uniform microdroplets with high reproducibility and resolution. The droplet transfer mechanism relies on the highly localized absorption of strongly focused femtosecond laser pulses underneath the free surface of the liquid contained in a reservoir. An analysis of the influence of laser pulse energy on the morphology of the printed droplets is carried out, revealing a clear correlation between the printed droplet dimensions and the laser pulse energy. Such correlation is interpreted in terms of the dynamics of the liquid displaced by a laser-generated cavitation bubble close to the free surface of the liquid. Finally, the feasibility of the technique for the production of miniaturized biosensors is tested.

Femtosecond pulsed laser microfabrication of SiC MEMS microgripper

We report the capability of an ultrafast laser to pattern an electrostatic-comb-drive microgripper in the chemically difficult-to-etch 3C-SiC thin films. A microgripper with overall dimensions 1.2 mm×0.35 mm and a gap of 20 μm was designed and fabricated for the purpose of grasping and transporting microscale objects in hostile and harsh environments. Atmospheric pressure chemical vapor deposition was used to deposit thin films (∼2 μm) of 3C-SiC on 〈100〉 silicon substrates. A Ti:sapphire laser with 120 fs pulse width, 800 nm wavelength, and 1 kHz repetition rate was then used to perform “nonthermal” micromachining of thin films. Subsequent KOH anisotropic etching was used to dissolve the silicon substrate and release the gripper structures. The influence of laser pulse energy on the etch rate and quality of microfabricated grippers was examined and illustrated.

Weld metal microstructural characteristics in pulsed Nd: YAG laser welding

Experimental investigations were carried out to examine the influence of laser pulse energy, duration, and travel speed on weld dimension, microstructure and hardness during overlap laser bead on plate spot welding of low carbon steel. Effective peak power density is defined for taking into account the effect of overlapping. It was found that even with full penetration welds there can be significant variation in the microstructure and hardness of weld within a weld spot due to the very rapid solidification.

Internal energy of ions generated by matrix-assisted laser desorption/ionization.

To provide an objective measure of the correlation between the internal energy content of ions generated by matrix-assisted laser desorption/ionization (MALDI) and the matrix properties, a series of well-characterized benzyl-substituted benzylpyridinium salts were used as thermometer molecules (TMs). To determine the internal energy variations of analyte ions, the survival yields of TM molecular ions were measured in three different matrixes, alpha-cyano-4-hydroxycinnamic acid (CHCA), 3,5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid, SA), and 2,5-dihydroxybenzoic acid (DHB). Statistical analysis of extensive survival yield data indicated that there were discernible differences among the studied matrixes. The experimental survival yields of the TM ions were used to calculate the unimolecular decomposition rate coefficient. Corresponding theoretical reaction rate coefficients were calculated based on the Rice-Ramsperger-Kassel-Marcus (RRKM) theory for different internal energies of the TMs. The internal energies of the ions were obtained by projecting the experimental rate coefficient values onto the theoretical curves obtained by the RRKM calculations. Molecular ions of the analytes showed decreasing survival yields and consequently increasing internal energies in the three matrixes in the following order: CHCA, SA, and DHB with "cold", "intermediate", and "hot" characteristics, respectively. Qualitatively, this could be interpreted as a significant departure from earlier observations suggesting an opposite trend. The classification as hot and cold matrixes should be further qualified by accounting for the influence of laser pulse energy and the nature of the analyte. Higher laser pulse energy led to an elevated level of energy transferred to the analyte, which in turn resulted in a diminished survival yield of the analyte molecular ion. It is quite possible that the assignment of hot and cold reverses as the analyte or the laser energy changes. These findings can help predict the outcome of postsource decay experiments and clarify the concept of hot and cold matrixes in MALDI mass spectrometry.