Proper Laser Parameters Research Articles

Application of digital twins for simulation based tailoring of laser induced graphene

In the era of man–machine interfaces, digital twins stand as a key technology, offering virtual representations of real-world objects, processes, and systems through computational models. They enable novel ways of interacting with, comprehending, and manipulating real-world entities within a virtual realm. The real implementation of graphene-based sensors and electronic devices remains challenging due to the integration complexities of high-quality graphene materials with existing manufacturing processes. To address this, scalable techniques for the in-situ fabrication of graphene-like materials are essential. One promising method involves using a CO2 laser to convert polyimide into graphene. Optimizing this graphitization process is hindered by complex parameter interactions and nonlinear terms. This article explores how these digital replicas can enhance the fabrication of laser-induced graphene (LIG) through laser simulation and machine learning methods to enable rapid single-step LIG patterning. This approach aims to create a universal simulation for all CO2 lasers, calculating optical energy flux and utilizing machine learning to control and predict LIG conductivity (ability to conduct current), morphology, and electrical resistance. The proposed procedure, integrating digital twins in the LIG production process, will avoid or reduce the preliminary tests required to determine the proper laser parameters to reach the desired LIG characteristics. Accordingly, this approach will reduce the time and costs associated with these tests and thus increase the efficiency and optimize the procedure.

Femtosecond laser upgrading the quality of bismuth films to enhance ultra-broadband photodetection.

Topological insulator bismuth has attracted considerable attention for the fabrication of room-temperature, wide bandwidth, and high-performance photodetectors due to the gapless edge state and insulating bulk state properties. However, both the photoelectric conversion and carrier transportation of the bismuth films are extremely affected by the surface morphology and grain boundaries to limit optoelectronic properties further. Here, we demonstrate a strategy of femtosecond laser treatment for upgrading the quality of bismuth films. After the treatment with proper laser parameters, the measurement of average surface roughness can be reduced from Ra = 44 nm to 6.9 nm, especially with accompany of the evident grain boundary elimination. Consequently, the photoresponsivity of the bismuth films increases approximately 2 times within an ultra-broad spectrum range from the visible to mid-infrared. This investigation suggests that the femtosecond laser treatment can help to benefit the performance of topological insulator ultra-broadband photodetectors.

Printing via Laser-Induced Forward Transfer and the Future of Digital Manufacturing.

In the last decades, digital manufacturing has constituted the headline of what is starting to be known as the 'fourth industrial revolution', where the fabrication processes comprise a hybrid of technologies that blur the lines between fundamental sciences, engineering, and even medicine as never seen before. One of the reasons why this mixture is inevitable has to do with the fact that we live in an era that incorporates technology in every single aspect of our daily lives. In the industry, this has translated into fabrication versatility, as follows: design changes on a final product are just one click away, fabrication chains have evolved towards continuous roll-to roll processes, and, most importantly, the overall costs and fabrication speeds are matching and overcoming most of the traditional fabrication methods. Laser-induced forward transfer (LIFT) stands out as a versatile set of fabrication techniques, being the closest approach to an all-in-one additive manufacturing method compatible with virtually any material. In this technique, laser radiation is used to propel the material of interest and deposit it at user-defined locations with high spatial resolution. By selecting the proper laser parameters and considering the interaction of the laser light with the material, it is possible to transfer this technique from robust inorganic materials to fragile biological samples. In this work, we first present a brief introduction on the current developments of the LIFT technique by surveying recent scientific review publications. Then, we provide a general research overview by making an account of the publication and citation numbers of scientific papers on the LIFT technique considering the last three decades. At the same time, we highlight the geographical distribution and main research institutions that contribute to this scientific output. Finally, we present the patent status and commercial forecasts to outline future trends for LIFT in different scientific fields.

Ultraviolet Laser Sintering of Printed Nickel Oxide Nanoparticles for Thin-Film Thermistor via Aerosol Jet Printing Technology

In this study, nickel oxide (NiO) thin films were printed by an aerosol jet printer, which is capable of fabricating thin films on the curve substrate via air stream. To approach high efficiency fabricating thin film thermistors in small batch sizes, the printed NiO nanoparticle thin films were sintered by using a 355 nm wavelength ultraviolet (UV) laser; this novel fabrication method reduced several steps of the conventional manufacturing process of the thermistor. Compared with furnace heat treatments of the NiO thermistor in previous studies, the UV laser sintering not only significantly improved the electrical properties but decreased the treatment time from an hour to a second. Since the resistance declined, the thermistor has been operated at an ambient temperature, which provides ready measurement. The resistance and morphology of the thin films were analyzed for evaluating the effect of the laser treatment. To identify the proper UV laser parameters, three laser parameters, including laser output energy, frequency, and scanning speed, were studied. Due to the laser-sintering parameters, namely, 2 W, 150 mm/s, 90 kHz, and a B value of 4683 K, the resistance has been reduced from 106.8 MΩ to 6.15 MΩ at 100 °C. The experiments exhibited a series of analyses for sintering states and defects of printed NiO nanoparticle thin film, which were sintered by UV laser. For NiO nanoparticles, UV laser has higher absorption energy than that of other wavelength lasers, when excess laser output was applied to the NiO thin film, cracks were observed on the surface. It was found that the crystal plane distances were not affected by recrystallization, but the cracks were based on the XRD analysis. Based on the analysis, there were obvious regional compressive stains before the appearance of cracks, and the uneven shrinking strains caused the cracks on the surface as energy irradiation increased.

Unified Model for Laser Doping of Silicon from Precursors.

Laser doping of silicon with the help of precursors is well established in photovoltaics. Upon illumination with the constant or pulsed laser beam, the silicon melts and doping atoms from the doping precursor diffuse into the melted silicon. With the proper laser parameters, after resolidification, the silicon is doped without any lattice defects. Depending on laser energy and on the kind of precursor, the precursor either melts or evaporates during the laser process. For high enough laser energies, even parts of the silicon’s surface evaporate. Here, we present a unified model and simulation program, which considers all these cases. We exemplify our model with experiments and simulations of laser doping from a boron oxide precursor layer. In contrast to previous models, we are able to predict not only the width and depth of the patterns on the deformed silicon surface but also the doping profiles over a wide range of laser energies. In addition, we also show that the diffusion of the boron atoms in the molten Si is boosted by a thermally induced convection in the silicon melt: the Gaussian intensity distribution of the laser beam increases the temperature-gradient-induced surface tension gradient, causing the molten Si to circulate by Marangoni convection. Laser pulse energy densities above H > 2.8 J/cm2 lead not only to evaporation of the precursor, but also to a partial evaporation of the molten silicon. Without considering the evaporation of Si, it is not possible to correctly predict the doping profiles for high laser energies. About 50% of the evaporated materials recondense and resolidify on the wafer surface. The recondensed material from each laser pulse forms a dopant source for the subsequent laser pulses.

Femtosecond Laser Writing of Spin Defects in Hexagonal Boron Nitride

Optically active spin defects in wide-bandgap materials have many potential applications in quantum information and quantum sensing. Spin defects in two-dimensional layered van der Waals materials are just emerging to be investigated. Here we demonstrate that optically-addressable spin ensembles in hexagonal boron nitride (hBN) can be generated by femtosecond laser irradiation. We observe optically detected magnetic resonance (ODMR) of hBN spin defects created by laser irradiation. We show that the creation of spin defects in hBN is strongly affected by the pulse energy of the femtosecond laser. When the laser pulse number is less than a few thousand, the pulse number only affects the density of defects but not the type of defects. With proper laser parameters, spin defects can be generated with a high probability of success. Our work provides a convenient way to create spin defects in hBN by femtosecond laser writing, which shows promising prospects for quantum technologies.

Effect of laser parameters on ultra-short laser processing of SiC

Crystalline silicon carbide (SiC) is a very attractive material in the fields of microelectronics, MEMS and biomedicine mainly due to its chemical inertness and mechanical strength. It is used for SiC MEM sensors, micro motors and resonators [1]. In the biomedical field, SiC is emerging as a promising material for additional coating of biomaterials due to its other useful properties (hardness, lightness, impermeability and good compatibility). For instance, in combination with bioglass, it is used for bone regeneration and as coating of some metal alloys, as it forms a bone-like layer on the surface upon contact with body fluids [2]. We studied the results of microporous modifications on the SiC surface irradiated by ultrashort laser pulses in view of further biomedical applications. The nanostructures were formed on the surface of a silicon carbide sample by using a regeneratively amplified Ti:sapphire femtosecond laser emitting at 800 nm. The SiC samples were irradiated as the laser light parameters (power, energy and number of applied pulses) were varied and the surface morphological changes were investigated. Modification of the topography of the silicon carbide substrates could substantially improve the bioactivity properties of this material, which, after proper laser parameters optimization, could make its biomedical application even more successful.

Impact of laser parameters on additively manufactured cobalt-chromium restorations

Statement of problemThe selective laser melting (SLM) process has become popular for the fabrication of frameworks for metal-ceramic restorations, although their surface roughness is greater than with cast or milled frameworks. Limited information is available regarding the surface mechanical characteristics of cobalt-chromium (Co-Cr) SLM-manufactured restorations. PurposeThe purpose of this in vitro study was to adapt the laser parameters for a remelting strategy, scanning the outer boundary of Co-Cr specimens, to reduce surface roughness and solidification defects, to determine microhardness, to investigate surface morphology and microstructure, and to establish surface mechanical characteristics. Material and methodsCo-Cr specimens were SLM manufactured by using a typical melting (TM) strategy and an adaptive remelting (AR) strategy. The AR strategy involves rescanning 50% of the contour, varying the laser parameters. The roughness parameters considered were Ra and Rz. Vickers hardness was measured by microindentation with a 9.81-N force (ASTM E384-17). The surface morphology was investigated by scanning electron microscopy, the chemical composition by energy-dispersive X-ray spectroscopy, and the phase identification by using X-ray diffraction. The mechanical surface properties measured were the nanohardness, elastic modulus, and dissipation energy. One-way ANOVA with the Tukey procedure was used to compare the groups (α=.05). ResultsThe innovative AR strategy reduced the surface roughness by 45% compared with TM, comparable with their cast counterpart. The smoothest AR surface was obtained by using 75 W and 350 mm/s for the first scanning of the contour, followed by a second remelting with 80 W and 700 mm/s. The microstructure of AR specimens had limited solidification defects, a chemical composition similar to that of raw powder, and a surface microhardness over 600 HV1. A fine grain structure in a single matrix phase was detected both on TM and AR specimens. The mechanical characteristics of the smoothest Co-Cr surface were 218 GPa elastic modulus, 746 HVIT Vickers nanohardness, 21 243 pJ plastic energy, and 26% nanoindentation work ratio. Significant differences were observed between the melting strategies (P<.05) both for surface roughness and microhardness. ConclusionsThe laser scanning strategy affects both the surface roughness and the hardness of SLM-manufactured specimens. The results show that using the AR strategy and proper laser parameters can reduce the roughness and increase the surface hardness of Co-Cr specimens made of conventional powder feedstock.

Rare-earths doped-nanoparticles prepared by pulsed laser ablation in liquids

This feature article highlights the recent advances on the lanthanide-activated nanoparticles prepared by pulsed laser ablation in liquids (PLAL). In the past decade, rare-earths-activated nanoparticles have been recognized from various applications including lots of high-tech products, green technologies, bioimaging and medical utilization. To obtain inorganic nanoparticles with different morphologies and sizes, pulsed laser ablation in liquids is a green and versatile technique. In this paper, a survey of the nanoparticle's formation during the laser ablation in the liquids is first introduced. We focus on the control of the size and morphology through proper laser parameters, choice of the reaction solution and proper surfactants. In the last part of the paper, we successfully prepared persistent luminescent SrAl2O4: Eu2+, Dy3+ by laser ablation in liquids and their optical features are investigated.

Frustrated double ionization of atoms in strong laser fields.

With a three-dimensional classical ensemble method, we theoretically investigated frustrated double ionization (FDI) of atoms with different laser wavelengths. Our results show that FDI can be more efficiently generated with shorter wavelengths and lower laser intensities. With proper laser parameters more FDI events can be generated than normal double ionization events. The physical condition under which FDI events happen is identified and explained. The energy distribution of the FDI products - atomic ions in highly excited states - shows a sensitive wavelength dependency.

Automatic Process Parameters Tuning and Surface Roughness Estimation for Laser Cleaning

An image analysis-based two-stage process parameters tuning and Surface Roughness (SR) estimation algorithm is proposed for the laser cleaning application. A Cartesian coordinate robot is utilized to collect image and implement cleaning. Before cleaning, in order to tune the proper laser parameters, first, the environment lighting is controlled for the metal image collection. Second, lots of classification features are computed for the images above. The Gray-Level Co-occurrence Matrix (GLCM) texture features, the concavo-convex region features, the histogram symmetry difference feature, and the imaging thermophysical property features are computed. Third, the initial laser parameters are created randomly and an iteration computation is performed: a Support Vector Machine (SVM) is used to forecast the cleaning effect; its inputs include the classification features and the initial laser parameters; its output is the cleaning effect degree. If the SVM output cannot fulfill user’s demand, the laser parameters will be updated randomly. This iteration will be implemented constantly until the SVM output becomes valid. Then the laser cleaning will be performed. When estimating SR for the cleaned metal, multiple image features are calculated for the images after cleaning. The features include the Tamura coarseness, some GLCM features, and the convex region feature. To improve the prediction precision, different feature combinations are used for different cleaning effects. The linear function and the 3-order polynomial function are considered for the SR estimation. After tests, the accuracies of SVM, the SR prediction function, and the integrated SR control and estimation algorithm can be 90.0%, 80.0% and 80.0% approximately.

Laser-assisted micro-grinding of Si3N4

One of the main challenges in micro-machining of hard to cut materials is the accuracy of the machined part because of high grinding forces which cause tool deflection and rapid tool wear. Non-conventional machining processes have been developed as alternatives to conventional processes for optimizing the machining efficiency and achieving the desired tolerances. This paper addresses a novel Laser-Assisted Micro-Grinding (LAMG) process. For the first time, an ultra-short pulse laser is used to structure micro-grinding tools and a Si3N4 workpiece prior to the micro-grinding. The induced grinding forces and achieved surface roughness as well as the tool deflection and wear by the LAMG process are compared to the Conventional Micro-Grinding (CMG) process. Additionally, the ultra-short pulsed laser ablation process was simulated to find the proper laser parameters corresponding to the desired structure and laser-cut depth. The results proved an enhanced performance of LAMG process in micro-grinding of Si3N4. Using the simulation, the depth of laser cut prior to structuring could be predicted. Structuring, either the workpiece or the tool, significantly reduced the grinding forces. However, a rougher surface resulted via tool structuring. The grinding forces reduced up to almost 40% using 30% structured workpiece surfaces. Structuring the micro-tool (10% structuring) resulted in 60% reduction in the grinding forces with around 40% rougher surface. The accuracy of the part was highly improved by the laser structuring. The actual depth of cut using CMG was 30% lower than the nominal depth of cut. Utilizing LAMG the total nominal depth of cut was removed from material. The comparison between the topography of structured and non-structured tools indicated higher tool wear and shorter tool life with the non-structured tool.

Development of a model for the simulation of laser surface heat treatments with use of a physical simulator

Nowadays, laser hardening is a sufficiently mature process to be industrially applied as a substitute for traditional heat treatments that are more expensive and less flexible. The bottleneck of the process is the difficulty in pre-determining the proper laser parameters able to produce the desired hardness depth and profile into the work-piece without trial and error tests which are very time consuming. To overcome this limitation and to increase the diffusion of laser hardening in industry, a low time consuming but accurate model of the laser hardening process is presented in this paper. The process simulation is able to determine the hardness depth in both single and multiple passes, considering tempering effects in the overlapping zones. The experimental procedure for the evaluation of thermo-dynamic parameters governing micro-structural transformations is also explained. The proposed process simulation can be used for two and three-dimensional analyses indistinctly and has been validated in the present work on an industrial benchmark (the surface hardening of an AISI 9840 cam).

Laser-Assisted Osteotomy for Implant Site Preparation

The aim of this study was to review the scientific evidence about the laser osteotomy in implant bed preparation. An electronic search was performed on relevant English articles up to April 2016 in the PubMed, Scopus, and Google Scholar databases. Twenty-two articles (1 clinical, 13 animal, and 8 ex vivo studies) were included. Implant sites prepared by erbium family lasers and drill showed comparable results regarding the percentage of bone-to-implant contact, values of biomechanical tests, and healing process. Selection of proper laser wavelength and parameters was of paramount importance to minimize the risk of thermal bone damage. Lack of depth control and long time needed for implant site osteotomy with laser were the most challenging concerns for its clinical applicability. Computer-guided laser osteotomy showed promise for future use of laser osteotomy in clinical settings. Evidence from animal studies shows promising results regarding laser osteotomy in implant site preparation. However, because of the lack of clinical studies, it is not possible to make a conclusive result whether there is superiority of laser osteotomy in clinical practice.

Realizing three-step photoionization of calcium by two lasers

In this paper, we report a new method to load \(^{40}\hbox {Ca}^{+}\) into ion traps. We show that the three-step photoionization process, which is stimulated by laser light at 423, 732 and 830 nm, can be realized by two lasers at 423 and 732 nm. Compared to the original three-step method, the new scheme has a more simple experimental setup and similar loading efficiency can be achieved with proper laser parameters. The loading efficiency as a function of the 732 nm laser power and detuning is also experimentally investigated.

Laser Scored Machining of Fiber Reinforced Plastics to Prevent Delamination

Delamination is a major problem in contour milling of fiber reinforced plastics (FRP) causing scrap or rework. Today, delamination avoidance limits overall productivity and tool life. Damage of the top layer of a composite structure is initiated if fibers are not cut during first engagement of the cutting edge, but deflected. Generated cracks propagate due to recurrent contact of fibers with the rotating tool. In contrast, when laser cutting FRP, the heat input often leads to an extensive heat-affected zone (HAZ), particularly in case of large laminate thickness and high energy input. Combination of both processes is a promising approach to overcome the mentioned disadvantages. Experiments indicate that pre-scoring of the top layer is possible with negligible HAZ for FRP materials using proper laser parameters, especially low energy input per unit length. Positioning of the laser scored kerf along the contour to be manufactured by the subsequent milling tool prevents crack propagation along the fiber direction even with a heavily worn milling tool at increased feed rate. Furthermore, laser pre-scoring eliminates protruding fibers and allows for edge chamfering. The process understanding is enhanced using simulation of the laser pre-scoring, particularly considering heat conduction and forced convection, as well as by presenting a model for the mechanism of delamination prevention.

THE EFFICACY OF LASER GLAZING ON SURFACE ROUGHNESS AND STRUCTURE OF ALL-CERAMIC VENEERS

aim of the study : This study was designed to set up proper laser parameters including laser type, power intensity and time of application for glazing of a particular glass-ceramic. The effect of laser glazing of the glass-ceramics on structural and roughness was investigated, evaluated and compared with the recommended glazing technique. material and methods :The materials used in this study were two commercially available lithium disilicate ceramics, fabricated by two different techniques: conventional lost wax (Injectable heat – pressed) and machinable Computer Aided Design / Computer Aided Manufacturing (CAD/ CAM) techniques. A total of 50 ceramic samples in the form of discs (5mm diameter and 2 mm thickness). For CAD/ CAM samples, a total of 50 discs were done sequentiallyin the Cerec 3 CPUacquisition unit. Two glazing techniques were adopted to the studied ceramic samples namely; conventional glazing and laser glazing. For each material subjected to the different glazing protocols structural Analysis, Surface Roughness was measured before and after glazing using white light Profilometry. results: Results of surface roughness (Ra) of the two investigated materials; IPS E-max press and IPS E-max CAD using two different surface treatments; conventional glazing and laser glazing in comparison to the control group are presented. For of M1; IPS E-max press material ANOVA results showed that the control group had the significantly highest surface roughness followed by laser glazing, while the conventional glazing showed the significantly lowest mean surface roughness (p <0.001). Regarding M2; IPS E-max CAD material no significantly difference was found between conventional glazing and laser glazing. conclusions:Within the limitations of the current study, the following conclusions were drawn: 1. Conventional glazing can be considered as the most reliable glazing technique as regard surface roughness. 2. Laser glazing with high power density increased the surface roughness of lithium silicate based ceramics.

Optimization of shunt isolation processing for silicon solar cells via laser and chemical etching

Abstract We employ laser scribing combined with chemical etching process to isolate the shunts in industrial off-spec or non-prime crystalline solar cells. Liquid crystal sheet and Infrared camera measurements have been carried out to reveal the existence of the shunts and hot spot temperature under reverse bias. Following laser scribing with proper laser parameters, chemical etching has been used to further optimize the isolation effect. Through illuminated current–voltage characteristic measurements, the improved open circuit voltage, fill factor and efficiency have been obtained. These results demonstrate that this combined shunt isolation process has great potential for its application in the solar cells.

The Effectiveness and Safety of Combining Laser-Assisted Liposuction and Abdominoplasty

Lipoabdominoplasty is nearly a daily aesthetic procedure. Despite the emergence of laser-assisted liposuction, to date, it has not been clearly evaluated combined with abdominoplasty. This prospective study aimed to evaluate the effectiveness and safety of laser-assisted liposuction relative to traditional liposuction combined with high-lateral-tension abdominoplasty. This study investigated 36 consecutive female patients who underwent high-lateral-tension abdominoplasty combined with liposuction of the upper central abdomen and both flanks. The patients were divided into three equal groups based on the technique used for liposuction. Group 1 underwent conventional liposuction with abdominoplasty. Group 2 underwent a mixture of conventional and laser-assisted liposuction with abdominoplasty. Group 3 underwent laser-assisted liposuction with abdominoplasty. The patients in groups 2 and 3 had a better aesthetic outcome than those in group 1 with regard to abdominal contour and skin tightness. No major complications were observed in groups 1 and 2. The patients in group 3 had a higher incidence of complications (3 seromas, 3 central necroses and dehiscence), and one patient underwent secondary sutures. Laser-assisted liposuction combined with abdominoplasty in the lateral abdomen seems to be a safe technique with good aesthetic outcomes. Although the combined use of laser-assisted liposuction in the lateral and central abdomen can achieve relatively better aesthetic results, it is associated with significant complications, and its use cannot be supported. Proper laser parameters in the central abdominal area still need further study. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Microstructural effects on the wear behavior of a biomedical as‐cast Co‐27Cr‐5Mo‐0.25C alloy exposed to pulsed laser melting

In this work, the effect of pulsed laser melting on the exhibited microstructure and properties of a cast Co-27Cr-5Mo-0.25C alloy was investigated. In particular, properties such as surface hardness and wear behavior of the laser modified microstructure were determined as a function of the implemented laser melting parameters. It was found that laser melting promotes significant grain refinement while preventing the precipitation of coarse carbide phases. Apparently, a refined dendritic grain structure develops which is surrounded by a fine carbide distribution in the interdendritic regions. Moreover, the high-temperature face centered cubic (FCC) phase remains untransformed at room temperature. Hardness measurements and wear testing using a Pin-On-Disk tribological machine indicate that the modified laser surfaces exhibit both, high wear resistance and high microhardness when compared with the untreated as-cast Co-27Cr-5Mo-0.25C alloy. In particular, it was found that the laser modified surfaces exhibit improved wear and friction properties comparable to the ones found in Co-Cr-Mo alloys with a predominantly hexagonal closest packed (HCP) matrix. However, surface defects associated with the laser process can be detrimental for the improved wear performance and they should be considered in identifying the proper laser parameters in alloy melting.