Laser Energy Research Articles

Efficacy of echolaser smart interface-guided laser ablation in volume reduction of symptomatic benign thyroid nodules.

The management of benign symptomatic thyroid nodules until recent years has been limited to surgery, radioactive iodine treatment, or surveillance which is associated with the burden of morbidity of complications or symptom non-relief as well as cost. Laser ablation has emerged as a minimally invasive alternative, this uses laser energy to thermally ablate nodule tissue, leading to volume reduction and symptom relief. Long-term treatment response data is growing but remains limited in the United States. Our study aims to quantify the effectiveness of laser ablation in reducing the volume of thyroid nodules over a 12 to 18-month period. Retrospective review of data was conducted for 63 adults with cytologically benign, solid symptomatic thyroid nodules ranging from 1.333 cm3 to 103.794 cm3 in volume. Ultrasound-guided laser thermal ablation was performed on all nodules using EchoLaser X4 Smart Interface device with 1064 nm diode laser to deliver total ablation energy (joules), calculated per device guidelines. Serial sonographic volume measurements were conducted 1 month, 3 -6 months, 6 - 12 months, and 12 to 18 months post-ablation intervals. Study cohort was comprised of 63 thyroid nodules. reduction in nodule volume increased progressively over time, with median reductions of 46.05% [STD 21.8] at 1 month, 60.33% [STD 20.1] at 3-6 months, 68.69% [STD 18.8] at 6-12 months, and 64.04% [STD 19.27] at 12-18 months. A total of 62, 56, 42, and 17 nodules had available data for analysis at these respective intervals. This study demonstrated a marked progressive reduction of thyroid nodule volume following ablation. The treatment appears to be consistently effective in reducing symptoms across a wide range of nodule sizes, although the degree of volume reduction varies. The results of our study underscore the potential of laser ablation as a viable treatment option for thyroid nodules, with a sustained reduction in nodule volume observed over an extended post-procedure period.

Micro-cracks generation and growth manipulation by all-laser processing for low kerf-loss and high surface quality SiC slicing

Low kerf-loss and high surface quality silicon carbide (SiC) wafer slicing is key to reducing cost, improving productivity, and extending industrial applications. In this paper, a novel all-laser processing approach is proposed by combining laser micro-cracks generation and growth manipulation. The first high fluence pulsed laser is applied to generate micro-cracks inside SiC, which increases its laser energy absorption. The second low fluence pulsed laser achieves the manipulation of micro-cracks growth and interconnection to separate SiC wafer. The optimal laser processing parameters are obtained to separate a 4H-SiC substrate at a thickness of 500 µm. The sliced surface is clean with average surface roughness (Sa) of 186 nm, standard deviation of 0.037, and kerf-loss of 915 nm. This laser slicing approach can be applied for high-hardness transparent material separation.

Roadmap on basic research needs for laser technology

Abstract Motivated by the profound impact of laser technology on science, arising from an increase in focused light intensity by seven orders of magnitude and flashes so short electron motion is visible, this roadmap outlines the paths forward in laser technology to enable the next generation of science and applications. Despite remarkable progress, the field confronts challenges in developing compact, high-power sources, enhancing scalability and efficiency, and ensuring safety standards. Future research endeavors aim to revolutionize laser power, energy, repetition rate and precision control; to transform mid-infrared sources; to revolutionize approaches to field control and frequency conversion. These require reinvention of materials and optics to enable intense laser science and interdisciplinary collaboration. The roadmap underscores the dynamic nature of laser technology and its potential to address global challenges, propelling progress and fostering sustainable development. Ultimately, advancements in laser technology hold promise to revolutionize myriad applications, heralding a future defined by innovation, efficiency, and sustainability.

Antibacterial performance of nanosecond laser irradiated zirconium-based bulk metallic glass.

Bulk metallic glasses (BMGs) have garnered significant attention in recent decades due to the outstanding physical, chemical, and biomedical characteristics. The biomedical application of metallic glass also received extensive attention. This report investigates the interplay among antibacterial performance, crystallization and processing parameters of Zr-based bulk metallic glass (Zr-BMG) following nanosecond laser irradiation. We examined surface morphology, crystallization behavior, surface quality, binding energy, and ion release properties post-laser irradiation. Additionally, we evaluated the generation of reactive oxygen species upon immersion of Zr-BMG in phosphate-buffered saline using the 2',7'-dichlorofluorescin diacetate method. Staphylococcus aureus was chosen to assess Zr-BMG's antibacterial performance, while mouse osteoblasts were utilized to investigate in vitro cytotoxicity. Our findings revealed that at laser energy intensities below 0.08 J/mm2, the amorphous structure of Zr-BMG remained intact after irradiation. Moreover, laser irradiation significantly enhanced the antibacterial performance of Zr-BMG. The release rate of ion, concentration of reactive oxygen species, and antibacterial properties exhibited direct proportionality to laser energy intensity. However, surfaces exhibiting high antibacterial efficacy also displayed elevated cytotoxicity. The surface irradiated with a 7 μJ ablation pulse and 200 mm/s irradiation speed demonstrated a superior balance between antibacterial and cytotoxic properties while maintaining an amorphous state. We hope this research can provide theoretical reference and data support for the application of metallic glass in biomedical application.

Effect of IR Laser Energy on Several Polymers Using LIBS Analysis

ABSTRACTThe focus of this research is to use the thermal ablation properties of a Nd:YAG infrared laser to highlight the thermal damage caused by the extinction of the plasma, which leads to the disappearance of the spectra of certain polymers as the laser energy increases. The study involved testing five commonly used polymers: polytetrafluoroethylene (PTFE) also known as Teflon, polyoxymethylene (POM), polyvinyl chloride (PVC), Bakelite, and polyamide. Laser induced breakdown spectroscopy (LIBS) analysis was used to qualitatively analyze the plasma generated from the polymer samples, identifying the excited species present in each of the five polymers. Wavelength dispersive X‐ray fluorescence (WDXRF) analysis of the polymer samples further confirmed the identification of these excited species. The results obtained from the spectra recorded at different laser energies in an air environment showed that the saturation observed in the plasma, induced by increasing laser energy, is not consistently observed for all polymers. This plasma extinction phenomenon in certain polymers is attributed to thermal effects when using an infrared (IR) laser as a heating source.

Automating Trace Detection and Chemical Purity Analysis of Carbon Nanotube Mixtures by Non-Negative Matrix Factorization of Spatial Raman Scattering Hyperspectra

Carbon nanotubes come in different species having different properties. So, it is useful to develop automated ways to quantify species purities and trace impurity content. Spatially scanned Raman spectra make hyperspectral data sets that can be used to discriminate between species and determine purities, and their analysis can be automated. A promising analytical machine learning approach is non-negative matrix factorization, which is a multivariate algorithm well adapted to hyperspectral Raman scattering data sets, and, significantly, available in open source. We prepare samples from different concentrations of pure nanotubes and acquire spatially scanned Raman scattering hyperspectra. We compare the known concentrations of the source dispersions to those determined from hyperspectra acquired from deposited materials on substrates. Here, we demonstrate and deal with several metrological issues: We show that the stability of the focusing conditions is critical. We show that if there are strong peaks that are not significant, normalization is helpful. We show that this approach compares favorably to the “best case” situation where the spectra are factored into a priori known library spectra. Scans of around 100 data points provided good bounds on concentrations down to about the parts per thousand level. Using more than one laser wavelength, so that different species are brought into resonance with each laser should enable higher relative purity measurements. However, there is an important consideration if the difference in laser energies is less than or comparable to the phonon energy. Overall, this approach is promising for the determination of chemical purity of carbon nanotubes and could be generalized to other chemical mixtures.

Microstructure formation mechanisms and property regulation methods during ceramic additive manufacturing

Anisotropic surface lamellar defects, dimensional shrinkage, and bending strength are important scientific issues that constrain vat photopolymerization additive manufacturing of biological, electronic, and core ceramics with high precision and complex structures. Through the single-factor experiment of photoinitiator concentration, average particle size, volume fraction, and refractive index constant in ceramic-resin slurry, this work studies the photopolymerization characteristics and profile curves, surface lamellar defects, and crosslinking density, verifies the reliability of the photopolymerization profile equations affected by the slurry composition, and acquires the anisotropic property formation mechanisms and control methods. The single-point scanning photopolymerization profile shape is parabolic, resulting in x-, y-, and z-direction lamellar defects before and after sintering (1550 °C), with no obvious weakening. After the quantitative description of the lamellar defects, the average surface roughnesses before and after sintering of the green body are 6.82 and 4.92 μm, respectively. Additionally, the laser energy attenuation along the penetration direction induces a gradient distribution of crosslinking density in the photopolymerization profile region. The crosslinking density gradient distribution of the decay from the slurry surface toward the depth direction is influenced by the slurry component concentration, leading to a gradient of cured powder concentration, which induces anisotropic behaviors. Through the crosslinking density controlling, the average bending strength in x(y) and z directions is increased by 63.19 % (46 %), the difference in anisotropic strength is reduced by 22.55 %, and the dimensional shrinkage difference of x and z directions is reduced by 48.32 %. This provides a theoretical and experimental research basis for ceramic vat photopolymerization with high dimensional accuracy, excellent performance, and morphology control.

Fabrication of high-quality surface microtextures on GaN by femtosecond laser direct writing

Gallium nitride (GaN), as a third-generation semiconductor, is highly attractive due to its exceptional physical and chemical properties. Laser direct writing offers an efficient method for the precise processing of hard and brittle materials. In this work, various types of surface microtexture were processed on GaN epilayers using a femtosecond laser with a wavelength of 1030 nm. The effects of the laser energy, single-pulse interval, number of pulses, and number of scan passes on groove machining were investigated with a view to achieving high-quality micromachining. The depth, width, surface morphology, and roughness of the grooves were analyzed using scanning electron microscopy, laser scanning confocal microscopy, and atomic force microscopy. Damage and stress were characterized at the microscale using Raman spectroscopy. High-quality precision machining of different types of periodic surface microtexture at 40 mW laser power was achieved by controlling the process parameters and laser trajectory. Finally, an initial exploration was conducted to examine vector-light-based micro- and nanostructure processing. The findings demonstrate the potential of femtosecond lasers for efficient micromachining of hard and brittle materials without the creation of heat-affected zones or microcracks. The high-quality textured structures achieved through this processing technique have broad and promising applications in optoelectronic devices and tribology.

Laser-structured anodes for high-power lithium-ion batteries: A journey from coin cells to 21700-type cylindrical cells

This study investigates the innovative use of lasers to modify anodes in lithium-ion batteries, targeting enhanced stability and performance in high-power applications. Although laser structuring of electrodes is well-documented, it is usually restricted to small areas and lab-scale cells. Our research stands out by implementing laser-structured electrodes in 21700-type cylindrical cells.Laser parameters, structuring patterns, and pit dimensions were meticulously optimized to reduce electrode tortuosity. Microstructural analyses verified that the active materials were not damaged by the laser energy during structuring. This structuring significantly decreased ionic pore resistance in the anode, as evidenced by symmetrical coin cell and half-cell studies. Intermediate upscaling with bi-layer pouch cells confirmed improved rate performance and long-term cycling stability, despite the low N/P ratio.As a final proof of concept, 21700 cylindrical cells were assembled with laser-structured anodes, resulting in a 42 % increase in CC charging capacity at 20 A and no lithium deposition issues. Discharge performance improved by 21 % at 30 A and 11 % at 35 A, with lower temperature increases. Despite some variability in the manufacturing process, the long-term cycling stability of the 21700 cells matched that of unstructured references, demonstrating the viability and potential of cylindrical TRL 4-level cells with laser-structured anodes.

Molecular dynamics research on the effect of selective laser melting parameters on porosity and properties of parts

Selective laser melting (SLM) is considered as a new production technology which has the potential to produce amorphous alloy parts. However, pores are often observed in parts prepared by SLM, which seriously affect the properties and life of the parts. In this work, an atomic model for SLM forming of Cu50Zr50 amorphous alloy is established. The effects of laser power and scanning speed on the porosity and mechanical properties of parts fabricate by SLM are researched using molecular dynamics methods. The results indicate that increasing laser power or reducing laser scanning speed could enhance the laser energy input of the molten pool and increase the molten pool temperature, which could improve the fluidity of the metal melt and prolong the existence time of the molten pool. The molten metal could fully fill the gaps between powders, which reduces the porosity and is beneficial to obtain dense parts. The tensile strength of samples formed by SLM is positively correlated with their porosity. Stress concentration occurs in the system with through holes and internal pores. Defects expand and interconnect rapidly under stress concentration, which leads to a decrease in strength and plasticity. The porosity could be reduced by adjusting the process parameters, thus improving the mechanical properties of the parts. This study provides a theoretical reference for a deeper understanding of the formation mechanism of SLM pores and the development of advanced alloys with high density.

A hybrid mesoscale-continuum approach to understand and predict melting kinetics of Al powders during laser processing

Abstract Laser interaction with metallic powders during additive manufacturing (AM) leads to fast heating and cooling rates that can affect the quality of the final products due to the formation of defects. One of the first steps towards predicting microstructures generated during AM, therefore, requires an accurate understanding of the laser energy deposition mechanisms that determine the melting kinetics at the level of individual powders. The critical challenge, however, is the availability of computational methods that can model the laser energy absorption, heat transfer, and the related microstructure evolution in individual metal powders at the length and time scales of AM. This manuscript demonstrates the capability of a novel scale-bridging methodology that combines the mesoscale quasi-coarse-grained dynamics (QCGD) simulations with a continuum two-temperature model (TTM) to account for the atomistic mechanisms of laser energy deposition and microstructure evolution and predict the kinetics of melting of individual powders at the experimental time and length scales. The scale-bridging capability of the hybrid QCGD-TTM simulations is demonstrated here by investigating the laser-induced microstructure evolution in aluminum powders with various sizes ranging from 200 nm to 20 µm. The analysis of the evolution of temperature, pressure, phase fraction, and melt fronts suggests the melting mechanism is heterogeneous due to the interaction with a laser, and the melting time is observed to decrease exponentially as the laser intensity increases. The solid-liquid interface velocity can be quantified to identify correlations with interface temperatures, and the predicted values satisfy the theoretically reported limits of crystal stability of metals against homogeneous melting. In addition, the pre-melting is found at the grain boundaries of 20 µm polycrystalline aluminum powder, while a minute contribution to melting is observed. This manuscript demonstrates the capability of the QCGD-TTM method to capture laser-powder interaction and allow the investigation of the kinetics of laser melting.

Reducing the total stimulated brillouin scattering of two-color lasers through two-ion decay

Abstract A mechanism coupling the stimulated Brillouin scattering (SBS) of two-color lasers with wavelengths of 527 and 351 nm via the two-ion decay 
instability is proposed. When the SBS reflectivities of both lasers exceed 10%, the ion-acoustic wave excited by the 527 nm laser seeds the decay process of the ion-acoustic wave excited by the 351 nm laser, thereby promoting the decay of the latter into the former. This results in a significant reduction in the SBS reflectivity of the 351 nm laser, while the SBS of the 527 nm laser exhibits minimal variation, consequently reducing the total SBS reflectivity. The total SBS reflectivity initially decreases and then increases as the intensity fraction α of the 527 nm laser rises. When α ∽(20%-30%), the laser energy reflections from both lasers become approximately equal, achieving the minimum total reflectivity. Through this mechanism, the incidence of the two-color lasers can achieve lower reflected energy compared to monochromatic lasers with the same total intensity. These results demonstrate the significant potential of replacing a small fraction of high-frequency light with low-frequency light in enhancing the laser-target coupling efficiency for inertial fusion energy.

Spectral behavior and expansion dynamics of Gd plasma generated by dual-pulse laser irradiation

Laser-produced gadolinium plasma (Gd-LPP) emerges as a promising candidate for next-generation nanolithography light sources. In this study, a dual laser pulse scheme was implemented to achieve a narrow spectral peak. By varying the pre-main pulse delay and pre-pulse laser energy, optimal conditions of 40 ns delay and 50 mJ energy were identified to improve spectral purity. Radiation hydrodynamics simulations revealed that the improved spectral purity stems from a flatter density gradient at the ablation front and a lower average electron density in the EUV emission region. Additionally, reheating the pre-formed plasma with a short main pulse mitigated plasma squeezing, resulting in an even lower electron density and thus improved spectral purity. Our findings suggest that spectral narrowing in the dual-pulse scheme, essential for better matching with multilayer reflection bandwidths, can be optimized through precise control of pre-pulse energy, pre-main delay, and main-pulse duration.

Ferroelectricity in Ultrathin HfO2-Based Films by Nanosecond Laser Annealing.

Nonvolatile memory devices based on ferroelectric HfxZr1-xO2 (HZO) show great promise for back-end integrable storage and for neuromorphic accelerators, but their adoption is held back by the inability to scale down the HZO thickness without violating the strict thermal restrictions of the Si CMOS back end of line. In this work, we overcome this challenge and demonstrate the use of nanosecond pulsed laser annealing (NLA) to locally crystallize areas of an ultrathin (3.6 nm) HZO film into the ferroelectric orthorhombic phase. Meanwhile, the heat induced by the pulsed laser is confined to the layers above the Si, allowing for back-end compatible integration. We use a combination of electrical characterization, nanofocused scanning X-ray diffraction (nano-XRD), and synchrotron X-ray photoelectron spectroscopy (SXPS) to gain a comprehensive view of the change in material and interface properties by systematically varying both laser energy and the number of laser pulses on the same sample. We find that NLA can provide remanent polarization up to 2Pr= 11.6 μC/cm2 in 3.6 nm HZO, albeit with a significant wake-up effect. The improved TiN/HZO interface observed by XPS explains why device endurance goes beyond 107 cycles, whereas an identical film processed by rapid thermal processing (RTP) breaks already after 106 cycles. All in all, NLA provides a promising approach to scale down the ferroelectric oxide thickness for emerging HZO ferroelectric devices, which is key for their integration in scaled process nodes.

The effect of laser energy on the size of WS2 quantum dots synthesized by pulsed laser ablation in liquid

The effect of laser energy on the size of WS2 quantum dots synthesized by pulsed laser ablation in liquid

Tailored porosity in additive manufacturing of 7075 aluminum alloy for crack suppression and high strength

Laser-directed energy deposition (LDED) additive manufacturing of 7075 aluminum (Al) alloy is highly challenging due to the inherent poor printability and high cracking tendency. Here, we disclose a new approach to suppress cracking in LDED-processed 7075 Al alloy by engineered porosity (about 1.14 %). The crack-free 7075 Al alloy was achieved by slightly sacrificing the densification. Further increasing the density of the material by increasing laser energy input leads to cracking. The mechanisms of minor pores in alleviating cracks are mainly reflected in three aspects: (i) pores disrupt the epitaxial growth of columnar grains; (ii) free-form surfaces surrounding pores could release the accumulated residual stress, and (iii) more dislocations near pore drive nucleation of near equiaxed grains. The LDED-processed crack-free 7075 Al alloy after heat treatment shows an ultimate tensile strength of 464 ± 12 MPa and break elongation of 9.7 ± 1.2 %, attaining a good strength-ductility synergy among many additively manufactured 7075 Al alloys in the current literature. Unlike the mainstream additive manufacturing of metallic materials, which pursues high densification to attain high-performance components, this work demonstrates the positive roles of pores in the additive manufacturing of cracking-sensitive materials. The findings of this work highlight new insights regarding the balance between pores and cracks for better manufacturability and higher mechanical performance of materials.

Photodetector application of CuO nanoparticles on porous silicon fabricated by laser ablation in liquid at diverse laser energies

Abstract This paper describes the synthesis and analysis of a photodetector made of copper oxide nanoparticles (CuONPs) embedded in a porous silicon (PS) matrix. CuONPs were generated utilizing pulsed laser ablation in ethanol (PLAL), while a porous silicon-(PS) substrate was created via photo-assisted electrochemical etching. An investigation is conducted on the optical, structural, and electrical characteristics of CuONPs/PS devices, with a focus on their dependence on laser energy. The X-ray diffraction analysis reveals the presence of distinct peaks associated with a copper cubic structure, demonstrating the successful synthesis of CuONPs that have been deposited onto PS. The study using field emission scanning electron microscopy revealed that the particles exhibited spherical form. The CuO-nanocolloids exhibited a linear relationship between laser power and absorption, and their surface plasmon resonance peaks were clearly visible at 570–590 nm. Band gaps of 1.70, 1.61, 1.81, and 1.90 eV were found for CuONPs produced at 500, 600, 700, and 800 mJ of laser energy, respectively, according to the optical characteristics. The greatest responsivity of the CuO-NPs/PS photodetector, manufactured at an energy level of 700 mJ, was 0.135345 A/W at 450 nm, as determined by the optoelectronic characteristics. As a result of combining PS with CuONPs, the devices shown in this work have the ability to function as highly efficient photodetectors.

A linearized hydrodynamic code for laser ablation and its application to laser pulse shaping for direct-drive fusion

One of the most harmful processes in inertial confinement fusion is Rayleigh–Taylor instability (RTI), and an efficient way to mitigate it is pulse shaping. However, because shaped laser pulses lead to unsteady ablation, it is insufficient to evaluate RTI based solely on the instability growth rate. Here, for better prediction of RTI during linear growth, hydrodynamic equations for laser ablation (including both balance and linearized perturbation equations) are solved numerically and used to optimize the laser pulse shape for direct-drive inertial confinement fusion. For given target conditions and laser energy, simulations show that a picket pulse before the main laser pulse can reduce RTI significantly, and it is clear that the reduction comes from two aspects: (i) the lower RTI seed due to rarefaction at the descending edge of the picket in the imprint stage and (ii) the smaller growth rate due to enhanced ablation velocity at the main pulse in the acceleration stage. It is found that the perturbed laser deposition in an underdense plasma also has a profound influence on RTI seeds in the imprint stage.

Diverse energy laser ablation in liquid for indium oxide nanoparticles on porous silicon: enhancing photodetector performance

Abstract The fabrication and analysis of a photodetector using copper oxide nanoparticles (In2O3-NPs) embedded in a porous silicon (PS) structure are detailed in this study. One method used to create In2O3 NPs was pulsed laser ablation in ethanol (PLAL), while another was photo-assisted electrochemical etching to create a porous silicon substrate. The optical, structural, and electrical features of In2O3-NPs/PS devices are investigated, with a particular emphasis on their variations with laser energy. After successfully applying In2O3 nanoparticles onto PS, the X-ray diffraction analysis revealed the presence of distinct peaks that correlate to a copper cubic structure. Using field emission scanning electron microscopy, the researchers determined that the particles had a spherical shape. Absorption increased with increasing laser intensity, and the In2O3-nanocolloids showed clear surface plasmon resonance peaks between 570 and 590 nm in wavelength range. Band gaps of 3.5, 3.4, 3.2, and 3.1 eV were found for the In2O3-NPs generated at 500, 600, 700, and 800 mJ of laser energy, according to the optical properties. According to the optoelectronic properties of the In2O3-NPs/PS photodetector, it was built with an energy level of 700 mJ and had a maximum responsivity of 0.2766 A/W at 650 nm. The In2O3NPs/PS devices discussed in this study have excellent photodetecting performance because they integrate In2O3-NPs with PS.

Simulation and experimental study of femtosecond laser ablation mechanisms of NiCoCrAlY coatings

To enhance the adhesion of turbine blade thermal barrier coating systems using the LST method, a thorough understanding of the ablation mechanism of NiCoCrAlY bond coat material by femtosecond laser systems is essential for producing high-quality textured grooves. This study systematically investigates the ablation mechanisms of NiCoCrAlY material, exploring the effects of laser energy density, laser scanning speed, and the number of laser scans on the ablation of NiCoCrAlY. Numerical simulations based on the two-temperature model were conducted, providing a comprehensive analysis of thermal effects, heat accumulation, and material response during the laser ablation process. The experimental results indicate that 1) the ablation phenomenon caused by heat accumulation becomes evident as the laser energy density increases from 1.948 J/cm2 to 4.521 J/cm2, with the accumulated heat reaching 1525.2 K, leading to distinct melting residues and heat-affected zones on the groove walls. 2) The change in laser scanning speed also affects heat accumulation. Using a laser scanning speed of 800 mm/s results in a high material removal rate, smooth machined walls, and a uniform surface with no significant heat-affected zones. 3) Excessively high numbers of laser scans shift the laser focus to the bottom of the groove. The high concentration of laser energy causes intense localized ablation, forming sharp bases with numerous cracks and melting residues. To achieve efficient and high-quality laser ablation, it is necessary to ensure that the number of scans remains below 40.