Laser Parameters Research Articles

A study on the influence of laser hardening on microstructure, and microhardness of additively manufactured H13

ABSTRACT Laser surface treatment was employed as a promising approach to enhance the fatigue life of additively manufactured samples by increasing the surface hardness of the material. In this study, H13 tool steel was manufactured using the selective laser melting method, and lines of laser treatment were applied to the surface. Experimental and statistical approaches were utilised to investigate the microstructural changes, microhardness variations, and weld geometry resulting from different laser treatment processes. The aim was to control the laser parameters and analyse the behaviour of the microstructure and hardness profile of the laser-treated zone. The results revealed an amelioration in the hardness of the laser-treated surface, except for the heat-affected zone, which exhibited a lower hardness compared to the substrate. Statistical approaches were employed to study the effect of laser parameters on the weld geometry including width and depth of the laser-treated area using ANOVA method, elucidating the impact of each factor on these values. Finally, a predictive method for estimating the width and depth was proposed, to facilitate the adjustment of laser parameters for achieving specific outcomes, such as desired hardness profiles or geometrical characteristics, in the laser surface treatment process.

Picosecond Laser Direct Writing of Micro-Nano Structures on Flexible Thin Film for X-Band Transmittance Function

Recently, ultrafast laser direct writing has become an effective method for preparing flexible films with micro-nano structures. However, effective control of laser parameters to obtain acceptable micro-nano structures and the effect of micro-nano structure sizes on function of the film remain challenges. Additionally, flexible films with high X-band transmittance are urgently required in aerospace and other fields. In this work, we evaluate the feasibility of applying picosecond laser direct writing for fabricating micro-nano structures on the surface of flexible thin film and the relationship between the size of square columnar micro-nano structures and the transmittance of the flexible thin film. The results show that an array of square columnar micro-nano structures was achieved by picosecond laser direct writing on the surface of flexible thin film (Au-SiO2-PI) with a thickness of 50 µm. Additionally, excellent micro-nano structures morphology of the square columnar arrays without burning through or destroying were obtained by laser direct writing with a pulse power and frequency of 2 W and 100 KHz, respectively. The results also show that the X-band transmittance was effected by the characteristic of the square columnar array on the surface of the flexible thin film. The X-band transmittance was significantly increased by decreasing the length of the square column on the surface of the flexible thin film. The X-band transmittance was slightly increased by decreasing the width of the groove of the square column on the surface of the flexible thin film.

Simulation and Experimental Study of the Single-Pulse Femtosecond Laser Ablation Morphology of GaN Films

Gallium nitride (GaN) exhibits distinctive physical and chemical properties that render it indispensable in a multitude of electronic and optoelectronic devices. Given that GaN is a typical hard and brittle material that is difficult to machine, femtosecond laser technology provides an effective and convenient tool for processing such materials. However, GaN undergoes complex physical and chemical changes during high-power ablation, which poses a challenge to high-precision processing with controllable geometry. In this study, the quantitative relationship between the parameters of a single-pulse femtosecond laser and GaN ablation morphology was investigated using isotherm distribution. A multiphysics model using COMSOL Multiphysics® was developed to generate the isothermal distributions. Experiments were conducted on the femtosecond laser ablation of GaN at various single-pulse energies, and the resulting ablation morphologies were compared with the predictions from the multiphysics model. The comparison demonstrated that the calculated isotherm distribution accurately predicted not only the ablation diameter and depth but also the crater shape across a broad range of laser fluences. The predicted errors of the ablation diameters and depths were within 4.71% and 10.9%, respectively. The root mean square error (RMSE) and coefficient of determination (R2) were employed to evaluate the prediction errors associated with the crater shapes, which fell within the range of 0.018–0.032 μm and 0.77–0.91, respectively. This study can provide an important reference for utilizing femtosecond lasers in the precise ablation of GaN to achieve desired geometries.

Protein-based microlasers: Continuous transition from whispering gallery mode to random lasing

Abstract Whispering gallery mode (WGM) and random biolasers are important for bio-integration and biosensing applications due to their biocompatibility. However, these two laser types typically require different fabrication techniques, and limited research has explored transitioning between them using the same fabrication process. In this work, we present a comprehensive investigation into the transition from WGM to random lasing in protein-based microsphere lasers. Through a dehydration method, we can fabricate dye-doped protein microspheres with diameters ranging from 20 to 150 µm. By varying the polystyrene (PS) particle concentration within these microspheres, we observed a continuous transition from WGM to random lasing under optical pumping, driven by enhanced light scattering as PS concentration increased. Key lasing parameters, including the lasing spectrum and lasing threshold versus laser size and PS concentration, were analyzed and compared. The results indicate that smaller microsphere lasers exhibit shorter lasing wavelengths. Particularly, a 63 µm WGM laser has a central lasing wavelength at 630 nm, while a random laser of similar size shows a peak wavelength at 590 nm, a 40 nm blue shift. The lasing threshold increases with smaller laser size and higher PS concentration, with WGM lasers requiring several µJ mm⁻², potentially ten times lower than random lasers. Our work opens the possibility of designing flexible, wavelength-tunable biological microlasers. Moreover, it provides an understanding of the distinct characteristics of WGM and random lasing, making a meaningful contribution to laser research.

Transscleral Pars Plana Choroid Ablation Using the Iridex Laser System Yields Improvements for Surgical Insertion of the Port Delivery Implant in a Minipig Model.

To evaluate an alternative surgical approach for Port Delivery System with ranibizumab (PDS) implant and a novel application of Iridex laser system in Gottingen minipig model. A total of seventeen male minipigs (Part 1: 9 animals in non-recovery and Part 2: 8 animals observed for 8-days post-surgery Part 2) received PDS implant insertion into each eye. The effect of Iridex 810 nm infrared diode laser with varying energy (power or duration) on transscleral pars plana ablation, surrounding ocular tissue and postsurgical vitreous hemorrhage (VH) was investigated. The most effective laser parameters for transscleral pars plana ablation in mitigating vitreous hemorrhage with no surrounding tissue damage were continuous wave mode, 1750 mW, 1000 ms, and 16 spots (8 overlapping spots/sweep applied over 2 rows) across a 4 mm segment, posterior to the limbus, delivering a total energy of 28 J. Minimal self-limiting scleral hemorrhage was observed with two of the implants and no VH were observed. µCT imaging was consistent with clinical ophthalmic. On microscopic observations, no tissue damage was observed at these laser settings. This Göttingen minipig model demonstrated a novel application of Iridex laser for transscleral pars plana ablation that streamlines the PDS implantation surgery.

Electroanalytical overview: the use of laser-induced graphene sensors.

Laser-induced graphene, which was first reported in 2014, involves the creation of graphene by using a laser to modify a polyimide surface. Since then, laser-induced graphene has been extensively studied for application in different scientific fields. One beneficial approach is the use of laser-induced graphene coupled with electrochemistry, where there is a growing need for disposable, conductive, reproducible, flexible, biocompatible, sustainable, and economical electrodes. In this mini overview, we explore the use of laser-induced graphene as the basis of electroanalytical sensors. We first introduce laser-induced graphene, before moving to the use of laser-induced graphene electrodes highlighting the various approaches and different laser parameters used to produce different graphene micro and macro structures, whilst describing how these structures are characterised and benchmarked for those working in the field of laser-induced graphene electrodes for comparison aspects. Next, we turn to the use of laser-induced graphene electrodes as the basis of electrochemical sensing platforms towards key analytes and its use in the development of biosensors. We provide a critical overview of the use of laser-induced graphene sensors compared to screen-printed and additive manufactured electrodes, providing future suggestions for the field.

Experimental Investigation of Laser-Induced Breakdown Spectroscopy on Submerged Solid Target Under Different Laser Parameters

Experimental Investigation of Laser-Induced Breakdown Spectroscopy on Submerged Solid Target Under Different Laser Parameters

X-ray tomography of polarization effects on deep laser-machined microgrooves

Ultrafast laser machining has been researched extensively over the last few decades to create features such as holes in a variety of materials. The effects of laser parameters including power and polarization on the dynamics of hole formation and resulting hole geometry have been studied. Grooves formation, especially deep ones, on the other hand, has not attracted as much attention, even though grooves are essential to most laser cutting operations. One aspect limiting the study of deep machined features such as grooves is the difficulty in imaging not only the geometry but also the associated collateral damage produced in the material during machining. Here, we employed x-ray tomography for three-dimensional imaging of deep ultrafast laser-machined grooves in various metals. The 3D images of the deep grooves were quantitatively analysed, revealing the significant effect of laser polarization on groove morphology. Under rotating polarization (also called “scrambled polarization” or “polarization trepanning”), the deep grooves are smooth and uniform, while under linear polarization, extensive branching is observed along the groove, and becomes more pronounced with increasing laser energy and groove entrance length. A mechanistic picture based on laser light reflection off the groove walls is proposed to qualitatively explain the polarization-dependent groove branching observed experimentally. These findings provide new insights into high-precision deep groove laser machining, highlighting the effectiveness of x-ray tomography as a powerful tool for in-depth three-dimensional studies of laser machining processes.

In-situ tailoring the microstructure and properties of dual phase high entropy alloys with molten pool element mixing modulation by altering laser parameters in laser-powder bed fusion

In-situ tailoring the microstructure and properties of dual phase high entropy alloys with molten pool element mixing modulation by altering laser parameters in laser-powder bed fusion

Achieving superior strength-ductility combination in the heterogeneous microstructured Ti64 alloy via multi-eutectoid elements alloying with CoCrFeNiMn during laser powder bed fusion

ABSTRACT The formation of coarse needle-shaped α′-Ti within columnar β-Ti grains in additively manufactured titanium alloy components is nearly unavoidable, and it can lead to unforeseeable service failures. This study employs a multi-component eutectoid alloying strategy, integrating CoCrFeNiMn high-entropy alloy particles within Ti64 alloy. By varying laser parameters, the resulting microstructure transitions from β-dominated to a metastable β + nanoscale α′ microstructure. The coarse needle-shaped α′-Ti and columnar β-Ti grains are significantly refined. Concurrently, the multi-component eutectoid alloying strategy successfully suppresses the formation of detrimental intermetallic compounds by promoting the uniform distribution and solubility of the alloying elements. The Ti64-(4.5%) CoCrFeNiMn alloy demonstrates exceptional mechanical properties, including high tensile strength (1333.8 MPa), uniform elongation (9.3%), and a work-hardening capacity (>390.0 MPa). These are attributed to the continuous variation of Co, Cr, Fe, Ni, and Mn concentrations within the ultrafine α′ and metastable β-phase regions, providing a progressive transformation-induced plasticity effect.

Surface quality analysis of microchannels fabricated through laser micromachining on PMMA for microfluidic applications

Micromachining is a widely employed technique for generating micro features across diverse applications. Laser micromachining has gained significant attention due to its inherent flexibility, precision, and ability to process a wide array of materials. In the era of miniaturization, laser has proven to be sustainable choice of process in the field of micromachining. Within laser machining, CO2 laser machining is considered to be an economical option. However, challenges persist in achieving both a high surface finish and a variable cross-sectional profile for microchannels. This study focuses on the investigation, identifying and categorizing of defects in microchannels machined by laser on polymethyl-methacrylate. Laser parameters are systematically varied to optimize the surface quality of the machined channels. Microchannels, fabricated through a full factorial experiment, are visually assessed using an optical microscope. The channels with the highest and lowest ratings are selected for further confocal and scanning electron microscope (SEM) analysis to comprehensively study the identified defects. The surface roughness is found to be 0.675 µm for the high-quality channel. A good surface finish at both the valley and side wall, along with a well-formed edge bulge was found at this condition.

Improvement of UV-photodetector using nanoparticles synthesized by laser ablation in liquid: A review

Laser ablation in liquid (LAL) has emerged over the past decade as a powerful technique for the synthesis of nanomaterials and the fabrication of functional nanostructures. Its ability to tackle diverse challenges in nanotechnology highlights its growing significance. This review systematically evaluates recent advancements in LAL, focusing on the synthesis of nanocrystals and nanostructures. We begin by outlining the fundamental principles of the LAL process, with particular attention to critical laser parameters such as pulse wavelength, duration, pulse width, repetition rate, energy density (fluence) and the characteristics of the ablation medium. The review then explores the mechanisms that govern nanoparticle formation, with an emphasis on the control of particle shape and size during synthesis. Recent studies on LAL-generated nanomaterials, including bismuth oxide (Bi2O3), silver nanoparticles (Ag NPs) and germanium nanoparticles (Ge NPs), are discussed, highlighting their applications in ultraviolet photodetection. Key advantages of LAL, along with its limitations, are critically assessed, and potential strategies for overcoming these challenges are proposed. We conclude by identifying future research directions that will help advance the application of LAL in nanotechnology, particularly in the field of UV photodetectors.

Miniaturization Potential of Additive-Manufactured 3D Mechatronic Integrated Device Components Produced by Stereolithography

Three-dimensional Mechatronic Integrated Devices (3D-MIDs) combine mechanical and electrical functions, enabling significant component miniaturization and enhanced functionality. However, their application in high-temperature environments remains limited due to material challenges. Existing research highlights the thermal stability of ceramic substrates; yet, their reliability under high-stress and complex mechanical loading conditions remains a challenge. In this study, 3D-MID components were fabricated using stereolithography (SLA) 3D-printing technology, and the feasibility of circuit miniaturization on high-temperature-resistant resin substrates was explored. Additionally, the influence of laser parameters on resistance values was analyzed using the Response Surface Methodology (RSM). The results demonstrate that SLA 3D-printing achieves substrates with low surface roughness, enabling the precise formation of fine features. Electric circuits are successfully formed on substrates printed with resin mixed with Laser Direct Structuring (LDS) additives, following laser structuring and metallization processes, with a minimum conductor spacing of 150 µm. Furthermore, through the integration of through-holes (vias) and the use of smaller package chips, such as Ball Grid Array (BGA) and Quad Flat No-lead (QFN), the circuits achieve further miniaturization and establish reliable electrical connections via soldering. Taken together, our results demonstrate that thermoset plastics serve as substrates for 3D-MID components, broadening the application scope of 3D-MID technology and providing a framework for circuit miniaturization on SLA-printed substrates.

High Performance GaSb-Based DBR Laser with On-Chip Integrated Power Amplifier via Gain-Match Design

We reported on a single-longitudinal-mode operated distributed Bragg reflector laser diode emitting at 1950 nm with an on-chip integrated power amplifier. Second-order Chromium–Bragg gratings are carefully designed and fabricated at the end of the ridge waveguide. Achieving a stable single-mode operation with a large injecting current range of 800 mA from 15 °C to 40 °C. The maximum side-mode suppression ratio (SMSR) is up to 42 dB. To increase the output power, an on-chip integrated master oscillator power amplifier (MOPA) is also introduced. MOPA-DBR lasers with different matching configurations between the gain peak and Bragg wavelength are fabricated, resulting in various amplification consequences. The best device is realized with 40 nm red-shifted between Bragg wavelength and photoluminescence (PL) peak. A power amplification of 5.6 times is achieved with the maximum output power of 45 mW. Thus, we put up the feasibility and key design parameters of on-chip integrated power amplification DBR lasers towards mid-infrared.

Femtosecond Laser-Induced Photothermal Effects of Ultrasmall Plasmonic Gold Nanoparticles on the Viability of Human Hepatocellular Carcinoma HepG2 Cells.

Laser-induced photothermal therapy using gold nanoparticles (AuNPs) has emerged as a promising approach to cancer therapy. However, optimizing various laser parameters is critical for enhancing the photothermal conversion efficacy of plasmonic nanomaterials. In this regard, the present study investigates the photothermal effects of dodecanethiol-stabilized hydrophobic ultrasmall spherical AuNPs (TEM size 2.2 ± 1.1 nm), induced by a 343 nm wavelength ultrafast femtosecond-pulse laser with a low intensity (0.1 W/cm2) for 5 and 10 min, on the cell morphology and viability of human hepatocellular carcinoma (HepG2) cells treated in vitro. The optical microscopy images showed considerable alteration in the overall morphology of the cells treated with AuNPs and irradiated with laser light. Infrared thermometer measurements showed that the temperature of the cell medium treated with AuNPs and exposed to the laser increased steadily from 22 °C to 46 °C and 48.5 °C after 5 and 10 min, respectively. The WST-1 assay results showed a significant reduction in cell viability, demonstrating a synergistic therapeutic effect of the femtosecond laser and AuNPs on HepG2 cells. The obtained results pave the way to design a less expensive, effective, and minimally invasive photothermal approach to treat cancers with reduced side effects.

Surface Enhancement of Titanium Ti-3Al-2.5V Through Laser Remelting Process-A Material Analysis.

This study evaluates the effects of laser parameters on the surface remelting of the Ti-3Al-2.5V alloy. A ms-laser equipped with a coaxial gas-pressure head integrated into a Swiss-type turning machine is used for the laser remelting process of cylindrical parts. The influence of different pulse frequencies, as well as varying intensities, is investigated. The results reveal that surface micro-cracks can be eliminated through laser remelting. Increasing the input laser intensity also increases the size of the melting pool. A similar effect is observed with higher pulse frequencies. The metallurgical microstructure and the size of the heat-affected zone of the remelted surface at different input laser energy levels are also examined. The results indicate that input laser energy influences phase transformation in the metallurgical microstructure, which correspondingly results in variations in micro-hardness within the heat-affected zone. The variations in laser fluence lead to a surface hardness improvement of approximately 15%.

Outcomes of Flapless Er:YAG and Er,Cr:YSGG Laser-Assisted Crown Lengthening: A Systematic Review.

In recent years, erbium-doped yttrium aluminum garnet (Er:YAG) and erbium, chromium/yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers have been introduced as another possibility to perform less-invasive flapless (FL) crown-lengthening (CL) procedures. The aim of this review is to describe the outcomes and complications of this approach. A literature review was conducted to retrieve clinical studies and case reports that analyze different variables related to laser-assisted flapless crown lengthening and report their outcomes in terms of gingival margin level stability (GMLS), and postoperative complications. A total of five studies were included in the final qualitative analysis; two of them were randomized controlled trials (RCTs) and the rest were case reports. The common variable measured in all studies was the GMLS, finding good stability in the FL groups at 3 months follow-up, but more tissue rebound was observed in patients with the thick biotype. Other variables were reported in different articles as the plaque index (PI), gingival index (GI), bone margin level, biotype, bleeding on probing (BP), probing depth (PD), and postoperative pain by the numeric rating scale (NRS). There are a wide range of heterogenous clinical variables used to evaluate outcomes, as well as variations in the type of laser used and its parameters in terms of the applied technique. However, most analyzed studies showed better GMLS for the flapless technique, as well as less postoperative inflammation. The included studies showed promising clinical outcomes in the FL laser-assisted CL groups concerning GMLS at the 3-month postoperative period. However, more RCTs are needed with respect to fixed laser parameters and patient biotype selection to reach a definitive clinical protocol.

The Use of Nanosecond Pulsed Fibre Laser Treatment to Improve the Corrosion Resistance of 316L SS Utilised as Surgical Devices.

The nanosecond pulsed fibre laser (NsPFL) treatment is extensively employed to distinguish hospital surgical instruments (micro-surgical forceps, surgical blades, orthopaedic drills, and high-precision laparoscopic tools), which are generally composed of stainless steel. Nevertheless, if the laser parameters are not properly optimised, this process may unintentionally provoke corrosion. Maintaining the structural integrity of these materials is essential for ensuring patient safety and minimising long-term costs. This work aims to optimise the laser scanning parameters for marking 316L stainless steel (316L SS), seeking to improve its corrosion resistance. The corrosion behaviour was assessed by using open circuit potential (OCP), potentiodynamic polarisation curves (PPc), and electrochemical impedance spectroscopy (EIS) techniques, conducted in 0.9% wt NaCl solution at a controlled temperature of 25 ± 1 °C. A comprehensive study employing optical profilometry has significantly enhanced our understanding of the corrosion micromechanisms of 316L SS, comparing specimens both with and without NsPFL treatment. Considering applications involving environments rich in chloride ions, the results indicated that the NsPFL-316L SS samples demonstrated markedly enhanced performance compared to the untreated base material after 48 h of immersion in 0.9% wt NaCl solution. This improvement is particularly noteworthy given the widespread utilisation of 316L SS in the manufacturing of surgical instruments, where corrosion resistance is of paramount importance.

Effects of CO2 laser parameters on quality of laser cut beech wood (Fagus sylvatica L) surface and extent of heat affect zone

Effects of CO2 laser parameters on quality of laser cut beech wood (Fagus sylvatica L) surface and extent of heat affect zone

Optimizing Femtosecond Texturing Process Parameters Through Advanced Machine Learning Models in Tribological Applications

Surface texturing plays a vital role in enhancing tribological performance, reducing friction and wear, and improving durability in industrial applications. This study introduces an innovative approach by employing machine learning models—specifically, decision trees, support vector machines, and artificial neural networks—to predict optimal femtosecond laser surface texturing parameters for tungsten carbide tested with WS2 and TiCN coatings. Traditionally, the selection of laser parameters has relied heavily on a trial-and-error method, which is both time-consuming and inefficient. By integrating machine learning, this study advances beyond conventional methods to accurately predict the depth and quality of textured features. The ANN demonstrated superior predictive accuracy among the models tested, outperforming SVM and Decision Trees. This machine learning-based approach not only optimizes the surface texturing process by reducing experimental effort but also enhances the resultant surface performance, making it well-suited for applications in sectors such as automotive and oil and gas.