Laser Parameters Research Articles

The Effect of Laser Structuring on Hot-Press Joined Metal-Polymer Cross Tension Joints

Abstract This study examines the effects of laser surface structuring on the cross-tension strength of metal-polymer hybrid joints, focusing on ASTM A1008 steel and two polymers: high-density polyethylene (HDPE) and polyamide with 50% glass fiber (PAGF50%). By varying laser parameters—such as power, scan speed, repetition count, hatch distance, groove patterns, and polymer thickness—the results show that optimal joining strength for steel-HDPE cross-tension specimens is achieved when the hatch distance is smaller than the effective groove width, which includes the recast structures, with minimal influence from repetition count and pattern. Notably, thicker HDPE specimens (5 mm) exhibited up to 54% greater joining strength than thinner ones (3 mm), attributed to enhanced resistance to deformation. Maximum strength for PAGF50% was achieved with a single repetition and a transverse groove pattern, leveraging recast structures that promote chemical bonding. Analysis indicates that cross-tension specimen strength is generally lower than that of T-joints due to edge-initiated fractures, underscoring the importance of specimen dimensions. These findings provide practical guidelines for optimizing laser structuring parameters to enhance joint performance in high-strength, lightweight metal-polymer applications.

Kramers - Henneberger Atoms in Flattened Gaussian Beams

Abstract The dichotomy structure is one of the prominent features of Kramers-Henneberger (KH) atoms. Within a focused laser field, the wave function of KH atoms becomes polarized due to ponderomotive (PM) forces induced by light intensity gradients, leading to the disruption of the dichotomy structure. In a Gaussian-focused laser field, the PM forces are negligible only along the optical axis. To maintain the dichotomy structure of KH atoms over a broader area, we compared the result of flattened Gaussian laser beams with Gaussian-focused laser beams. By calculating the wave functions of ground KH state hydrogen atoms at various radial and angular locations in the laser focusing plane, it was demonstrated that under suitable laser parameters, the dichotomy structure can be fully or partially preserved in flattened Gaussian laser beams. Through the dichotomy structure of KH atoms, we can verify the existence of KH atoms using interference fringes of multiphoton ionization signals.

In vitro study of the effects of diode laser on dentin hypersensitivity and evaluation of intra-pulpal temperature variation.

To evaluate the efficacy and safety of different wavelengths of high-power diode lasers for the treatment of dentin hypersensitivity by analyzing morphological changes and temperature variation. Human third molars were irradiated with five different commercially available lasers at wavelengths of 808nm, 940nm, 976nm, and 980nm, both with and without the use of a photoinitiator (activated charcoal). Temperature variations were monitored using thermocouples, and morphological changes were assessed through scanning electron microscopy. Lasers with wavelengths of 940nm, 976nm, and 980nm, used without a photoinitiator, promoted dentinal tubule obliteration without causing thermal damage. Lasers with wavelengths of 808nm, 940nm, 976nm, and 980nm, when combined with a photoinitiator, resulted in even lower temperature variation compared to the non-photoinitiator groups, although no regular fused surface was observed. Diode laser parameters, except Group 1(808nm without photoinitiator), are potentially safe for dentinal tubule obliteration. The use of a photoinitiator continues to be an effective strategy for minimizing temperature variations during irradiation.

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 microsphere random lasers (RLs) exhibit shorter lasing wavelengths. Particularly, a 63 µm WGM laser has a central lasing wavelength at 630 nm, while a RL 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 RLs. 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.

Enhancing the Optical Performance of Mid-Infrared Chalcogenide Glass Through Liquid Coating

Laser induced damage to optical component surfaces poses a critical challenge in the development of high-power laser systems. Such damage is typically influenced by its material host, defect distribution, laser parameters, and environmental conditions. The impact of surface defects becomes particularly pronounced under high-power, short-pulse laser irradiation, especially when surface roughness is suboptimal. In this study, we applied a liquid coating method to improve the surface quality of As2S3 glass under various surface conditions by eliminating defects with liquid. A detailed evaluation of the transmittance and surface laser damage threshold was conducted. The results reveal that effective liquid coating significantly reduces surface scattering and Fresnel reflection, resulting in up to a 24.8% increase in overall transmittance and a 2.17-fold improvement in the surface laser damage threshold. These findings underscore the critical role of liquid coating in enhancing optical material performance and offer a practical solution for optimizing high-power laser systems.

Safety parameters of diode laser therapy for the treatment of recurrent aphthous ulcers: a systematic review and meta-analysis.

The aim of this study is to evaluate the safety parameters of diode laser (DL) therapy on treating recurrent aphthous ulcer (RAU). We conducted a systematic review in accordance with the PRISMA guidelines. Studies from PubMed, Embase, WOS, Cochrane, Google Scholar, CNKI, Wanfang Data and VIP were searched by hand. The search terms encompassed both Medical Subject Headings terms (Stomatitis, aphthous; Lasers, semiconductor) and their corresponding text words. The meta-analysis was performed using Review Manager 5.4. 16 studies were included in this review with no high-risk studies and no significant publication bias. In this review, we found DL therapy was more effective than medication or placebo in reducing Visual Analog Scale (MD = 2.79, 95% CI: 1.40 to 4.17, P < 0.0001), shrinking ulcer size (MD = 2.62, 95% CI: 1.15 to 4.09, P = 0.0005) and accelerating healing time (MD = -3.72, 95% CI: -4.86 to -2.59, P < 0.00001). Moreover, subgroup analyses demonstrated that DL therapy effectively alleviated immediate pain in patients (MD = 2.88, 95% CI: 1.53 to 4.23, P < 0.0001), and a single exposure significantly shortened the healing time of RAU (MD = -4.20, 95% CI: -5.76 to -2.64, P < 0.00001). DL therapy is an effective treatment for RAU without any adverse effects. A single session (or two) with low-energy density irradiation significantly alleviates RAU symptoms. Consequently, there is no need to pursue longer durations and higher parameters of DL therapy, which also aligns with the economic interests of patients. RAU is typically painful and can impair quality of life. Suitable DL therapy represents a promising strategy.

One-Step Laser-Guided Fabrication of 3D Self-Assembled Graphene Micro-Rolls.

Laser-induced graphene (LIG) has been systematically investigated and employed because of the spartan laser synthesis and functional three dimensional (3D) foam-like structures. However, thermally induced deformation during laser processing is generally undesirable and, therefore, strictly suppressed. This work introduces a novel laser-guided self-assembly approach integrated into the fabrication of LIG to generate multiscale 3D graphene foam structures in a single step. Leveraging the photothermal effects of laser ablation on polyimide films, we achieve concurrent LIG production and self-assembly, enabling the transformation of two dimensional films into 3D micro-rolls. The process is finely tuned through interface modification and optimized laser parameters, allowing precise control over the geometry of the resulting structures. Systematic investigations reveal that varying laser power and line spacing effectively adjust the diameters of the LIG micro-rolls. Characterization indicates that the LIG micro-rolls can be fabricated with very large curvature and limited internal space, enhancing the potential for microscale applications. Furthermore, our laser strategy facilitates the creation of symmetric, asymmetric, and double-tube micro-rolls, underscoring its design flexibility. This work highlights the potential of the laser-guided self-assembly strategy in graphene nanomaterials and miniaturized applications, which has been exemplarily verified through the LIG micro-roll supercapacitors.

Evolution of autoresonant plasma wave excitation in two-dimensional particle-in-cell simulations

The generation of an autoresonantly phase-locked high-amplitude plasma waves to the chirped beat frequency of two driving lasers is studied in two dimensions using particle-in-cell simulations. The two-dimensional plasma and laser parameters correspond to those that optimized the plasma wave amplitude in one-dimensional simulations. Near the start of autoresonant locking, the two-dimensional simulations appear similar to one-dimensional particle-in-cell results (Luo et al., Phys. Rev. Res., vol. 6, 2024, p. 013338) with plasma wave amplitudes above the Rosenbluth–Liu limit. Later, just below wave breaking, the two-dimensional simulation exhibits a Weibel-like instability and eventually laser beam filamentation. These limit the coherence of the plasma oscillation after the peak plasma wave field is obtained. In spite of the reduction of spatial coherence of the accelerating density structure, the acceleration of self-injected electrons in the case studied remains at $70\,\%$ to $80\,\%$ of that observed in one dimension. Other effects such as plasma wave bowing are discussed.

Investigation of the modification intensity and distribution in silica glass via ultrafast laser direct writing

In ultrafast laser processing of silica glass, the laser-affected zone and heat accumulation of the ultrafast laser influence the modified intensity and distribution within the materials, subsequently affecting its optical, mechanical, and chemical properties. Although there have been some studies on the modification of silica glass, there is still a lack of detailed research on the relationship between laser parameters and the intensity and distribution of the modification. In this study, the effects of pulse energy densities and the number of burst modes on the intensity and distribution of silica glass modification were quantitatively investigated using a combination of Raman spectroscopy detection and simulation. The results indicated that as the pulse energy density increased, the modification intensity at the bottom of the groove after laser scanning was approximately 14% higher than that at the surface. When the pulse energy density was 314J/cm2 and the burst number was two, the internal modification intensity and distribution in silica glass exhibited a decreasing trend along the modification line region, with the modification intensity decreasing by an average of approximately 62%. This study enhances the ability to predict the intensity and morphology of ultrafast laser modified silica glass and provides theoretical guidance for preparing various silica glass components.

Influence of Laser‐Assisted Cutting on the Surface Integrity and Fatigue Life of FeCoCrNiAl0.6 High‐Entropy Alloy

ABSTRACTThis study explores the application of laser‐assisted cutting (LAC) in FeCoCrNiAl0.6 high‐entropy alloys to address traditional machining challenges and poor surface quality. It systematically analyzes the effects of laser power, scan speed, and spot diameter on surface integrity and fatigue life. Using Abaqus/FE‐SAFE simulations and LAC experiments, differences in surface quality and fatigue cycles under various laser parameters are observed. Results show that increasing the spot radius reduces heat accumulation and center temperature. A 1 mm radius yields a center temperature 5.58 times higher than a 7 mm radius and achieves a residual compressive stress of 412 MPa, which decreases to 198 MPa (51.9% reduction) at 7 mm. Larger laser power increases stress and fatigue life positively, while higher scan speeds reduce stress. Fatigue cycles drop by 82.9% as the spot radius increases from 1 to 7 mm, while 25 W power extends fatigue life 4.26 times compared to 10 W.

Graphene oxide-enhanced photothermal therapy: laser parameter optimization and temperature modeling for hela cancer cell mortality.

Photothermal therapy, in which a laser is an effective tool, is a promising method for cancer treatment. Laser parameters, including power, irradiation time, type of laser radiation (continuous or chopped), and the concentration of the photothermal agent, can affect the efficiency of this method. Therefore, this study investigated and compared the effects of different laser parameters on the efficiency of photothermal treatment for cervical cancer, which is the fourth most prevalent cancer in women. In addition, we investigated the properties of graphene oxide (GO) synthesized as a photothermal agent under laser radiation, and its effectiveness in achieving the desired therapeutic temperature. This study examined and compared the effects of temperature, nanoparticle concentration, irradiation time, and laser power to understand their impact on heat transfer. The toxicity of graphene oxide at different concentrations in HeLa cancer cells was also evaluated. These results demonstrated low toxicity, particularly after 24h, with approximately 10% toxicity. The study explored mortality under laser irradiation at various powers and time intervals using continuous and chopped beam irradiation. In addition, a model for temperature prediction using a regression tree was presented. Finally, the combined photothermal effects of graphene oxide and laser irradiation were investigated. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test results reveal significant effects, with a mortality rate of 90% in continuous radiation with a concentration of 0.3mg/ml and 75% in chopped beam irradiation with concentrations of 0.3 and 0.4mg/ml. A regression tree model was developed to predict temperature changes based on the GO concentration, laser power, and irradiation time, providing valuable insights for optimizing photothermal therapy parameters. Statistical analysis showed that the combined effect of graphene oxide with continuous laser irradiation was more effective than chopped-beam laser irradiation. However, the chopped-beam irradiation method is expected to cause less damage to surrounding tissues. These findings indicate that photothermal therapy with graphene oxide, chopped, and continuous laser irradiation can potently treat HeLa cancer cells and pave the way for further exploration of targeted cancer treatments.

Photophysical Investigation of Dyes and Dye-PMMA Systems: Insights into Absorption, Emission, and Charge Transfer Mechanisms.

The photophysical properties of five dyes, i.e., perylene, anthracene, aminoanthracene, 1,6-diphenylhexatriene, and 7-diethylamino-4-methylcoumarin, in solvent and attached to the poly(methyl methacrylate) (PMMA) polymer, were studied via DFT and TD-DFT calculations. Their absorption and emission spectra were calculated, while for the PMMA-dye systems, their absorption spectra were measured experimentally, in good agreement with the calculated ones. In the PMMA-dye systems, charge transfer from the dye to PMMA was observed, and in the case of perylene, electron transfer from its ground state was also observed. It was found that the PMMA-dye systems can interact photochemically via laser illumination, and provided that the charge transfer will be enhanced by using the appropriate laser parameters, the systems may be candidates for the design of materials for specific nanopatterning needs.

On the surface characterization of laser treated DIN 1.2379 tool steel

The following study aimed to optimize CO2 laser processing parameters for 1.2379 cold work tool steel to improve its surface properties. As its applications required high durability, strength, and precision, surface roughness and microhardness values were adjusted by varying laser power from 70% to 92%, laser speed from 1 to 5 mm/s, and stand-off distance from 4 to 6 mm. Using these background procedures, this specific study was performed to improve the manufacturing of tool steels used under extreme conditions. Scanning electron microscopy and profilometry were used to identify optimal settings that significantly improved the steel’s surface and subsurface appearances. A speed of 3 mm/s with a power of 81% and a stand-off distance of 5 mm resulted in minimized kerf width, kerf morphology, and spacing and improved uniformity. Using the energy dispersive x-ray spectrum, changes also measured in the distribution of elements, such as the increase in iron and chromium at the surface level of the steel. The effect of the parameters was quantified using analysis of variance (ANOVA) and the Taguchi method, which showed us the proportion of variance that could be described by the amount and specific parameters, with stand-off having the most impact. In this study, the specific effects of certain laser parameters on the microstructural and mechanical properties of cold work tool steel 1.2379 were recorded.

Optimizing laser-induced deep etching technique for micromachining of NXT glass.

Recent advancements in display technology have led to the development and diversification of complex glass materials. Among them, Corning's Lotus NXT glass offers excellent optical properties, high thermal stability, and dimensional accuracy, which are crucial for display applications. However, these characteristics make it difficult to apply pre-existing machining techniques developed for conventional glass materials directly to NXT glass. In this study, we used the laser-induced deep etching (LIDE) technique to fabricate micro holes in NXT glass. Various laser, chemical, and mechanical parameters were subjected to experimental analysis and optimization to achieve higher etching speed and aspect ratio. In this study, successful etching of Corning's Lotus NXT glass was achieved by optimizing laser parameters, including a wavelength of 1030 nm, a pulse energy of 45 µJ, a pulse count of 2 × 104, and a repetition rate of 40 kHz, combined with a chemical composition consisting of a 1:5 molar ratio of HF to HCl. This resulted in a high aspect ratio of ∼23:1 and an impressive etching speed of 1200 µm/h.

Differences in lasers and laser technologies: what does a clinician need to know?

This review focuses on recent advancements in laser technologies used in urology, particularly in enucleation, vaporization, lithotripsy, and focal laser ablation (FLA). The growing use of the thulium fiber laser (TFL) and the development of pulsed thulium lasers (p-Tm:YAG) highlight the relevance of this review, as these innovations aim to improve precision and outcomes in urological procedures. Recent studies have shown the advantages of TFL in achieving precise tissue ablation, reduced retropulsion offered by the Moses technology in holmium lasers, and the potential of pulsed thulium lasers for more precise control of the effects on tissues. Additionally, FLA is gaining traction for its ability to treat localized prostate cancer with minimal collateral damage. These technologies not only optimize procedural accuracy but also reduce complications, making them safer for high-risk patients, including those receiving anticoagulants. The advancements in laser technology, including TFL, Moses technology, and pulsed thulium lasers, are improving outcomes in urological surgeries by increasing precision, reducing operative time, and minimizing complications. FLA represents a promising alternative for minimally invasive cancer treatments. Ongoing research should focus on optimizing laser parameters and exploring broader clinical applications.

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.

Laser-induced graphene as an embedded sensor for impact damage in composite structures assisted by machine learning

Laser-induced graphene (LIG) enables the creation of cost-effective sensing devices via one-step laser scribing on organic substrates. This work aims to demonstrate the feasibility of LIG as an embedded damage sensor in structural composite materials. LIG was produced on an inexpensive cork substrate using a low-power blue light laser engraving system. The LIG was characterised to establish the relationship between the LIG’s physical properties and the lasing parameters. Using the lasing parameters which offer the optimal LIG properties, a LIG mesh pattern lased on the cork substrate was embedded in a glass fibre composite laminate as the damage-sensing core material to assess its sensing capability for impact damage. By measuring the electrical resistance change in the LIG mesh pattern consisting of a series of horizontal and vertical channels before and after impact loading, it was able to define the location of internal damage and its damage size, validated by X-ray computed tomography results. It is demonstrated that the test data can be used to train a machine learning algorithm to develop a simple damage-sensing system with a high accuracy rate of 94.3%, which significantly reduces the manual effort for large-scale composite structural health monitoring. This simple damage sensing system can be used to monitor internal impact damage in composite structures, such as off-shore wind turbine blades, which are inaccessible for inspection by conventional non-destructive testing.

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.&amp;#xD;