Laser-induced Plasma Plume Research Articles

Highly Efficient Laser Bidirectional Graphene Printing: Integration of Synthesis, Transfer and Patterning.

Graphene has tremendous potential in future electronics due to its superior force, electrical, and thermal properties. However, the development of graphene devices is limited by its complex, high-cost, and low-efficiency preparation process. This study proposes a novel laser bidirectional graphene printing (LBGP) process for the large-scale preparation of patterned graphene films. In LBGP, a sandwich sample composed of a thermoplastic elastomer (TPE) substrate, carbon precursor powder, and a glass cover is irradiated by a nanosecond pulsed laser. The laser photothermal effect converts the carbon precursor into graphene, with partial graphene sheets deposited directly on the TPE substrate and the remaining transferred to the glass cover via a laser-induced plasma plume. This method simultaneously prepares two face-to-face graphene films in a single laser irradiation, integrating synthesis, transfer, and patterning. The resulting graphene patterns demonstrate good performance in flexible pressure sensing and Joule heating, showcasing high sensitivity (7.7kPa-1), fast response (37ms), and good cycling stability (2000 cycles) for sensors, and high heating rate (1°Cs-1) and long-term stability (3000s) for heaters. It is believed that the simple, low-cost, and efficient LBGP process can promote the development of graphene electronics and laser manufacturing processes.

Laser-induced breakdown spectroscopy for helium detection in beryllium coatings

Laser Induced Breakdown Spectroscopy (LIBS) method is considered to be a promising tool for analyzing the retention of hydrogen isotopes (D and T) and helium (He) on the first walls and divertor regions of future fusion reactors. Helium will be produced in DT reactions but could also be used in the initial non-nuclear phases of DEMO concepts. The present study investigates the He detection by LIBS method in the Be coatings simulating the deposits on the divertor plasma-facing components of JET while the results are also relevant for He detection in the deposits of other wall materials. The study was carried out in a vacuum vessel filled with 2–40 mbar argon background gas. It was shown that 2.8 at. % of He was confidently detectable by LIBS at optimized measurement conditions and the estimated limit of detection at used experimental conditions is approximately 0.7 at. %. The intensity of the He emission line at 587.56 nm was the strongest at the center of the laser-induced plasma plume. The He line intensity increased with the pressure of Ar gas but the broadening of the He line and the increase of the background emission and noise set an upper limit to the Ar background pressure usable for He detection. The application of the calibration-free LIBS procedure resulted in the overestimation of the He/Be ratio by several orders of magnitude. The overestimation can be explained by the deviation of LIBS plasma from the local thermodynamic equilibrium, which is caused by the very high excitation energy of He atoms.

Lagrangian perspective on the expansion dynamics and shielding effect of femtosecond laser-induced copper plasma plumes

Femtosecond laser ablation of metals generates a strongly ionized plasma plume near the irradiated surface. The resulting plasma shielding effect can reduce subsequent laser energy deposition and lower nanomachining efficiency, especially during multi-pulse irradiation. Understanding the spatiotemporal evolution of the laser-induced plasma and its associated shielding effect is, therefore, crucial. A hybrid two-temperature and direct simulation Monte Carlo (TTM-DSMC) computational model is developed in this study, which synergistically couples the ultrafast laser–metal interaction physics and the plasma collisional transport. The model simulates the plasma properties including electron density, temperature dynamics, reflectivity, and energy attenuation throughout the plume expansion process from femtosecond to nanosecond timescales. A complex “penguin-shaped” plasma plume with internal shockwaves is observed due to the effects of double-pulse irradiation. Significantly enhanced plasma reflectivity and reduced laser energy deposition demonstrate the accumulated shielding effect, which increases with higher plasma density accumulation when the pulse separation is insufficient. Our model provides valuable theoretical guidance for optimizing processing parameters to enhance efficiency and precision in femtosecond laser machining. The integrated TTM-DSMC approach could also facilitate the study of laser-induced plasmas in other contexts like material characterization and nanoparticle synthesis.

Hydrodynamic expansion and plume splitting of the ultrafast laser-induced plasma during ablation of multi-element metallic materials under atmospheric condition

In this study, the hydrodynamic expansion and splitting effect of ultrafast laser-induced plasma plume for multi-element alloys were studied. A fully coupled hydrodynamic model for femtosecond laser ablation of multi-element alloys was presented to study the ambipolar electric field during the plume expansion process. The model utilized a level-set equation to capture the interface between the condensed phase and the gaseous phase and accounted for the reaction between different species. A time-gate direct fluorescence measurement was conducted for the target material of brass, a Cu–Zn alloy, to validate the simulation results. The simulation results showed good agreement with the experimental results and were able to predict the plume-splitting effect. The ambipolar electric field induced by charged particle distribution difference was studied in detail. It was found that the ambipolar electric field was the dominant cause for the acceleration of ions, which yielded plume splitting during the expansion process. The fully coupled HD model was further used to explore the effect of the beam spot size, laser fluence, and the pulse width on plasma plume splitting.

Development of laser-ablated aluminum plasma plume during the irradiation of laser pulse

In this paper, we theoretically simulate the dynamic evolution of plasma from the interaction between a nanosecond pulsed laser and aluminum targets. The self-luminous image of the plasma plume during the laser loading process was experimentally obtained using high-speed photography. Theoretical and experimental results demonstrated that the plasma shielding effect and plasma lateral expansion have a significant effect on the plasma plume. It will affect laser–target coupling and further affect the evolution of plasma plumes. The detonation wave contained in the early stage of the laser-induced plasma plume directly affects the subsequent shock wave.

Study of spatially confined copper plasma by probe beam deflection technique

In the last decade, laser induced plasma (LIP) has emerged as one of the most promising techniques for various applications. It is now commonly investigated using various expensive techniques. Probe beam deflection (PBD) is an inexpensive technique generally utilized to characterize the shock wave. In this work, the copper laser-induced plasma plume and shock wave are both investigated using PBD technique. The plasma is generated at atmospheric pressure using Nd:YAG laser at a low laser power density (0.8 GW/cm2). The contribution of the plasma plume components to the PBD signal is clarified in space and time. The spatial confinement effect by a metallic disk is also investigated. It approves the physical mechanisms responsible for the deflection signal. As well, the spatial distribution of the weak shock wave velocity is considered.

Double layer acceleration of ions with differently charged states in a laser induced plasma

The electric field driven acceleration of plasma ions is an intrinsic effect in laser-induced plasma plumes and is responsible for the generation of high-energy ions. At high laser fluences (≥ 2 J/cm2), multiply charged ions are formed and affect the plume expansion dynamics. In this paper, we used kinetic energy-resolved mass spectrometry to investigate the relative abundance and kinetic energy distributions of singly- and doubly-charged ions produced by KrF-laser ablation of nine different oxide targets. The doubly charged metal ions with a lower mass-to-charge (m/z) ratio show narrow energy distributions at high average kinetic energies coinciding with the cutoff energies for the singly-charged ion distributions. The observation suggests that the recombination of higher charged ions plays a prominent role in the formation of the high-energy tail for singly-charged ions. The results are discussed in terms of component volatility and a dynamic double layer, where ions with different m/z values experience different accelerations.

Analysis of Rare Earth Ores Using Laser-Induced Breakdown Spectroscopy and Laser Ablation Time-of-Flight Mass Spectrometry

Rare earth elements are gaining significant importance in the scientific and technological fields for their exciting physical properties and characteristics. The aim of the present study was to determine rare earth elements (REEs) in geological ores found in the Northern Areas of Pakistan. We present the application of laser-induced breakdown spectroscopy (LIBS) and laser ablation time-of-flight mass spectrometry (LA-TOF-MS) for the elemental analysis of geological ore samples containing REEs. The laser-induced plasma plume exhibits a wide array of emission lines, including those of rare earth elements such as Ce, La, and Nd. Furthermore, the spectral range, from 220 nm to 970 nm, encompasses emission lines from C, Fe, Ti, Na, Mg, Si, and Ca. The qualitative analysis of the constituent elements in the samples was performed by comparing the LIBS spectrum of the unknown sample with that of the spectroscopically pure rare earth elements (La2O3, CeO2, and Nd2O3, with 99.9% metals basis) recorded under the same experimental conditions. The quantitative analysis was performed using the calibration-free laser-induced breakdown spectroscopy (CF-LIBS), LA-TOF-MS, and energy-dispersive X-ray (EDX) techniques. The results obtained by CF-LIBS were found to be in good agreement with those obtained using the LA-TOF-MS and EDX analytical techniques. LIBS is demonstrated to yield a quick and reliable qualitative and quantitative analysis, of any unknown geological sample, comparable to that of the other analytical techniques.

Optical assessment of the spatial variation in total soil carbon using laser-induced breakdown spectroscopy

Soil carbon storage is a substantial factor in the global carbon cycle. Carbon sequestration in agricultural soils, and the assessment and validation of soil carbon storage, are crucial for the mitigation of agricultural greenhouse gas emissions and for steering towards sustainable farming practices. Enforcement and verification of carbon sequestration policies, methods, and models require extensive soil carbon monitoring capability. However, current conventional laboratory-based methods for soil carbon estimation are laborious, expensive, and time-consuming. In this work, we have developed a compact, robust, and field-capable experimental device based on laser-induced breakdown spectroscopy (LIBS) for the rapid assessment of total soil carbon content and its spatial distribution in mineral soils. The carbon content quantification was performed using a spectral line of carbon at a wavelength of 193.1 nm emitted from the laser-induced plasma plume. The LIBS measurements were performed on soil samples collected from 28 different locations and various depths (up to 1 m) of a test field cultivated with a forage legume (red clover - Trifolium pratense, L.) and grass (Timothy - Phleum pratense, L.) mixture in eastern Finland. A calibration model was established based on a limited and randomly chosen sample set and validated by comparing soil carbon estimates obtained from various locations in the test field using the dry combustion (LECO) method. Further, we demonstrate here the usefulness of LIBS methodology for mapping three-dimensional carbon distribution at the test field. We emphasize here that the calibration model can be generalized to other sample areas under similar soil type with a relative error of less than 10 % and possesses potential for fast on-site determination of spatial variation in total soil carbon, reducing substantially the need of time-consuming sample processing in laboratory. Therefore, LIBS enables frequent and extensive spatial and temporal soil carbon mapping and has the potential to become part of the future carbon monitoring network.

PLD plasma plume analysis: a summary of the PSI contribution

We report on the properties of laser-induced plasma plumes generated by ns pulsed excimer lasers as used for pulsed laser deposition to prepare thin oxide films. A focus is on the time and spatial evolution of chemical species in the plasma plume as well as the mechanisms related to the plume expansion. The overall dynamics of such a plume is governed by the species composition in particular if three or more elements are involved. We studied the temporal evolution of the plume, the composition of the chemical species in the plasma, as well as their electric charge. In particular, ionized species can have an important influence on film growth. Likewise, the different oxygen sources contributing to the overall oxygen content of an oxide film are presented and discussed. Important for the growth of oxide thin films is the compositional transfer of light element such as oxygen or Li. We will show and discuss how to monitor these light elements using plasma spectroscopy and plasma imaging and outline some consequences of our experimental results.

Comparison of light capturing approaches in Laser-Induced Breakdown Spectroscopy (LIBS) for multichannel spectrometers

LIBS technique requires the spectroscopic analysis of the light emitted by a laser-induced plasma plume. One challenge of the different approaches to capture the plasma light emission is the significant shot-to-shot variations of the plume inhomogeneities, position, and morphology. This is even more challenging when multichannel CCD spectrometers are used, because the light should be homogeneously divided among multiple capturing optical fibers (typically up to 8 fibers) with stable spectral efficiency for all channels. Otherwise, any further analysis of the atomic emission spectra involving multiple channels, such as line intensity ratios, Boltzmann plots, or calibration-free LIBS, could be compromised by the morphology-dependent spectral artifacts induced by the collection optics. In this work, we assess the performance of several collection optics in terms of overall capturing efficiency and channel-to-channel variations due to changes in plasma morphology. Results clearly show that this could be an issue even with the approaches with the best spatial homogenization, including optical fibers and Köhler optics.

Correction to: Hydrodynamic splitting of laser-induced plasma plumes: two-dimensional kinetic simulations

Correction to: Hydrodynamic splitting of laser-induced plasma plumes: two-dimensional kinetic simulations

Analysis of laser induced plasma plume in atmosphere using deep learning

Analysis of laser induced plasma plume in atmosphere using deep learning

High-Precision and Low-Damage Microchannel Construction via Magnetically Assisted Laser-Induced Plasma Ablation for Micro-Thermoelectric Devices.

Thermoelectric devices are developing toward high density and miniaturization with a large filling factor for new applications in chip thermal management and microenergy harvesting. Pulsed laser etching has become one of the most effective tools for the patterning construction of highly integrated micro-thermoelectric devices. However, the laser spot size and Gaussian laser energy distribution restrict the processing size and accuracy of microchannels. Moreover, the rapid temperature rise caused by laser energy injection would also raise serious problems such as element volatilization, cracks, and recast layers. Herein, a liquid-assisted nanosecond laser ablation technology with magnetically controlled plasma is proposed to etch microchannels on thermoelectric thick films. By evaluating the size and shape of microchannels, we theoretically investigated the influence of cavitation bubbles on the laser optical path and surface roughness in laser-induced plasma ablation. In addition, the energy criterion for high-precision ablation is revealed, and the effect of magnetic field on ablation threshold is explained by magnetic constraint on energy and kinetic properties of the laser-induced charged plasma plume. Finally, the high-precision and low-damage microchannels are achieved on Bi2Te3 thermoelectric thick films with a minimum line width of 19.12 μm and a small sidewall inclination degree of tan θ = 0.085. This work provides a promising alternative for the fabrication of high-density three-dimensional (3D) patterning in semiconductor microdevices.

Hydrodynamic splitting of laser-induced plasma plumes: two-dimensional kinetic simulations

Hydrodynamic splitting of laser-induced plasma plumes: two-dimensional kinetic simulations

Surface Structuring and Reverse Deposition of Nanoporous Titanium Oxides by Laser Ablation of Titanium in Air

The deposition of titanium oxides during titanium laser ablation in air has been experimentally and numerically investigated. A titanium sample was irradiated by nanosecond pulses from an Yb-fiber laser with a beam scanned across the sample surface for its texturing. As a result, the hierarchical structure was observed consisting of a microrelief formed by the laser ablation and a nanoporous coating formed by the reverse deposition from the laser induced plasma plume. The chemical and phase composition of the nanoporous coating, as well as the morphology and structure of the surface, were studied using scanning electron microscopy, atomic force microscopy, and X-ray microanalysis. It was found that the deposit consists mostly of porous TiO2 with 26% porosity and inclusions of TiO, Ti2O3, and Ti2O3N. Optical emission spectroscopy was used to control the plasma composition and estimate the effective temperature of plasma plume. The chemical-hydrodynamic model of laser induced plasma was developed to get a deeper insight into the deposition process. The model predicts that condensed titanium oxides, formed in peripheral plasma zones, gradually accumulate on the surface during the plasma plume evolution. A satisfactory agreement between the experimental and calculated chemical composition of the plasma plume as well as between the experimental and calculated composition and thickness of the deposited film was demonstrated. This allows a cautious conclusion that the formation of condensed oxides in the plasma and their consequent deposition onto the ablation surface are among the key mechanisms of formation of porous surface films.

Review on Vacuum Laser Beam Welding

Vacuum laser beam welding (VLBW) exhibits better welding characteristics, e.g., deep penetration, less pore, and spatter generation, compared with the conventional laser welding technique under atmospheric pressure. Low ambient pressure affects the vaporization temperature of the base material and the interaction between laser and plasma plume, which affects the behaviors of laser-induced plasma plume, keyhole, and weld pool flow. This review introduces improvements in welding characteristics such as penetration depth, pore, and spatter generation in the VLBW process. The effect of ambient pressure on welding characteristics was reviewed, and the behavior of laser-induced plume, keyhole, and molten pool under reduced ambient pressure was discussed to understand the mechanisms for enhanced weldability.

Spatiotemporal characterization of the laser-induced plasma plume in simulated Martian conditions

With ChemCam on NASA's Curiosity rover, SuperCam on NASA's Perseverance rover, and MarSCoDe on the Zhurong rover of the China National Space Administration, there are currently three instruments on Mars that employ laser-induced breakdown spectroscopy (LIBS) to analyze the chemical composition of Martian rocks and soils. With more than 880,000 LIBS measurements on Mars by ChemCam alone, the LIBS technique has been proven to be uniquely qualified for the in-situ robotic exploration of planetary surfaces. Since the laser-induced plasma exhibits a complex spatiotemporal evolution that has a significant impact on the recorded LIBS spectra, fundamental investigations of the plasma propagation and the spatial distributions of the plasma emissions can provide important insight that can help to improve the analysis of Martian LIBS spectra. Here we present first results from our LIBS plasma imaging setup, which allows us to spatially and temporally resolve the spectral emissions from the laser-induced plasma in simulated Martian atmospheric conditions. Investigating a calcium sulfate sample, we find that the commonly applied assumption of a nearly isothermal and homogeneous plasma with a colder outer layer is not sufficient to describe the laser-induced plasma on Mars. Instead, different spectral features show unique spatial distributions that suggest a strong influence of the outgoing shock wave. After plasma formation, the plasma center is found to rapidly become colder and more rarefied than the outer plasma regions. Molecular emissions are found to originate in this cold plasma center.

Influence of laser-induced plasma parameters on the formation of laser-induced surface-periodic structures

The paper presents the results of processing a silicon surface with subpicosecond laser pulses under various exposure conditions. The variable conditions were: pressure in the working chamber, the speed of scanning the silicon surface with a laser beam and the laser pulse energy. Special attention was paid to the interaction of the laser-induced plasma plume with the surface of the processed material, with laser radiation and with the medium. The influence of the medium on the parameters of the laser-induced plasma is estimated. The result of this interaction is a change in the spatial characteristics of the laser-induced plasma channel, the period and type of the formed periodic surface structures, what is related to the change in the laser radiation passing through the medium at different pressures.

Splitting of laser-induced neutral and plasma plumes: hydrodynamic origin of bimodal distributions of vapor density and plasma emission intensity

The splitting of laser-induced plumes into the fast and slow components is usually explained by acceleration of ions by the ambipolar electric field. The kinetic simulations show that the splitting is observed even in neutral plumes due to the snow-plow effect. In plasma plumes, the simulations predict bimodal distributions of plasma emission intensity, where the slow maximum appears due to radiation absorption during the laser pulse, while the fast maximum emerges after the pulse at the plume edge. The snow-plow effect explains why the fast component is observed in a limited range of ambient pressure, exists during a limited time, and is characterized by larger degree of ionization.