Laser Manufacturing Research Articles

Investigations on 355 nm picosecond laser machining of carbon fiber reinforced polymer composites

Carbon fiber reinforced polymer (CFRP) composites have emerged as excellent performance structural materials with a wide range of applications in the aerospace industry. Ultrafast laser is a promising and versatile tool for manufacturing these composites due to its advantages of high peak intensity and ultrashort pulse duration. Herein, a theoretical model based on the Fokker–Planck law and the two-temperature equation, i.e. the ultrafast responses of a two-dimensional heterogeneous material assembly of resin matrix padded with carbon fiber reinforced phase irradiation by 355 nm picosecond laser is established. The evolution of laser-excited free electron density is analyzed, and the relationship between the optical properties of substrate and electron density is revealed. The spatial and temporal distribution of electron and lattice temperatures are thus characterized. The ablation thresholds of resin and carbon fiber are determined, the accuracy of which are verified by experiments. On this basis, orthogonal experiments are conducted to analyze the influence law of process parameters on the ablation depth and heat affected zone (HAZ) width. Optimized parameter groups are discovered to realize the high-quality machining of CFRP composite with considerable depth-to-width ratio and limited HAZ width. This work offers new insight into the fundamental regimes and high-quality machining for picosecond laser manufacturing of CFRP composites.

Enhanced heat source modeling in particle-based laser manufacturing simulations with ray tracing

Particle-based spatial discretization methods such as smoothed particle hydrodynamics (SPH) possess suitability for the high-fidelity simulation of laser manufacturing processes due to their capability in treating complex free-surface and multiphase problems. In such simulations, laser heat source modeling remains a central concern as the mechanisms governing the material deformations and phase changes strongly depend on the input laser energy and its distribution details. Ray tracing (RT) is a realistic and accurate approach for high-fidelity heat source modeling that can capture surface heterogeneity and multiple reflections. However, RT heat source modeling for particle-based numerical methods faces additional challenges rooted in the lack of explicit surface representation, intensive computational efforts, and implementation complexities. This work addresses these issues by proposing an enhanced and efficient RT heat source model for particle-based laser manufacturing simulations with negligible computational overhead and without requiring background nodes or surface mesh reconstruction. After validating the RT heat source model versus analytical and experimental results, we assess its computational performance through two test cases, showing that the computing workload imposed by our RT model is between 0.1% and 25% of the total runtime in different SPH-based laser manufacturing simulations. With the achieved efficiency and robustness, it becomes convenient yet advantageous to simulate processes like laser drilling and laser powder bed fusion with precision far beyond the conventional approaches using volumetric heat sources.

Ultra-Fast Heating Process of Cu-Pd Bimetallic Nanoparticles Unraveled by Molecular Dynamics Simulation

This paper investigates the ultra-fast heating process of Cu-Pd bimetallic nanoparticles from an atomic-scale perspective, which is essential for laser manufacturing processes, such as laser cladding and selective laser melting. The behavior of high surface ratio nanoparticles during these processes is strongly influenced by their properties and the heating process, which is governed by atomic dynamics. Previous studies have mainly focused on the combination process in pure metallic nanoparticles under slow or isothermal heating, but this work demonstrates that the ultra-fast atomic dynamic process between bimetallic nanoparticles differs significantly. Specifically, in Cu-Pd nanoparticles, the combination process is primarily dependent on the surface atomic motion of the lower melting point particles rather than plastic deformation in the grain boundary between particles. Moreover, the ultra-fast heating process is size-dependent. For small nanoparticles, the atomic kinetics exhibit two different mechanisms depending on temperature: Low-temperature jointing is controlled by localized atomic rearrangement, while high-temperature coalition is governed by the atomic flow of surface atomic melting in the low-temperature melting particle. The combination mechanism is the same for large particles as it is for small particles at high temperatures. The findings of this study provide important insights into the behavior of bimetallic nanoparticles during ultra-fast heating and can inform the development of coat and lubricant.

Semi-Analytical Solution for Modelling Moving Heat Sources in a Semi-Infinite Medium with Radiative and Convective Boundary Conditions

The weld quality is highly related to the thermal history of the weld and there have been many trials to monitor the quality using an infrared (IR) sensor. To obtain the real temperature of a surface based on the brightness temperature values measured by an IR camera, the emissivity value must be derived. For an accurate assessment of the emissivity, one must be aware of the melting point isotherm. The temperature profiles only depend on three factors during laser processing, specified as constants the characteristics of the material: laser beam speed (v), laser beam diameter (d), and power (P). Predicting the width of the melted zone reached during the welding process as the parameters vary is a tool for helping a quality laser processing and for determination of true temperature in laser welding using IR camera. This study describes the semi-analytical (SA) solution of the heat conduction equation for a localized moving Gaussian heat source with constant parameters on a semi-infinite medium. The solution, simple and quick to obtain, provides information on the width of the melted zone with an average error < 5 %. The outcome is assessed numerically and contrasted with FEM solutions for a Gaussian source, the latter having undergone experimental validation. With two distinct defocus values, def0 and def-6, and by varying the speed and power settings, two separate types of experiments were run. Thus, the SA solution was obtained and compared after the FEM solution had been obtained with a good approximation (max err 4.3 %, average err 2.7 %). Only in regard to the 1AL test is an error more than 5 % detected; in the other case, the average error is 3.75 %. Two more tests at the defocus values of def-4 and def-8 were conducted to confirm the model's validity as the parameters varied. Overall, the average error between the semi-analytical and the FEM solution is 4.1%. The SA solution may be used to effectively estimate the isotherms related to the melting point of aluminum (770 K). This allows to obtain a tool which helps restoring the real temperature based on the brightness values measured by the IR camera during laser welding. At the same time, this effective tool allows to investigate the importance of different processing parameters in laser manufacturing.

Learning Complexity to Guide Light-Induced Self-Organized Nanopatterns.

Ultrafast laser irradiation can induce spontaneous self-organization of surfaces into dissipative structures with nanoscale reliefs. These surface patterns emerge from symmetry-breaking dynamical processes that occur in Rayleigh-Bénard-like instabilities. In this study, we demonstrate that the coexistence and competition between surface patterns of different symmetries in two dimensions can be numerically unraveled using the stochastic generalized Swift-Hohenberg model. We originally propose a deep convolutional network to identify and learn the dominant modes that stabilize for a given bifurcation and quadratic model coefficients. The model is scale-invariant and has been calibrated on microscopy measurements using a physics-guided machine learning strategy. Our approach enables the identification of experimental irradiation conditions for a desired self-organization pattern. It can be generally applied to predict structure formation in situations where the underlying physics can be approximately described by a self-organization process and data is sparse and nontime series. Our Letter paves the way for supervised local manipulation of matter using timely controlled optical fields in laser manufacturing.

Nonlinear Optical Wavefront Engineering with Geometric Phase Controlled All‐Dielectric Metadevice

AbstractOptical wavefront engineering with artificial nanostructures has important applications in laser manufacturing, bioimaging, optical communications, etc. In the linear optical regime, metasurfaces are widely utilized to realize wavefront engineering functionalities, such as imaging with a flat lens and generation of vortex beams and holographic images. On the other hand, it is highly desirable to directly control the wavefront of light during nonlinear optical processes. Here, the nonlinear optical wavefront engineering with geometric phase controlled all‐dielectric metadevices is experimentally demonstrated. This is realized by integrating the multifunctional dielectric metasurface with the conventional nonlinear optical crystals. It is demonstrated that the nonlinear metadevice can be used to generate optical vortices and nonreciprocal holographic images at second harmonic frequencies. The proposed all‐dielectric metadevice represents an important strategy to develop compact and multifunctional nonlinear optical sources.

Theoretical and experimental research on a spatially modulated femtosecond bessel-like laser for microdrilling in silica glass

Beam shaping has been widely used in laser processing. Compared with Bessel beam, Bessel-like beam has unique advantages of fabricating high-aspect-ratio holes due to its tunable and longer non-diffraction length. However, the theoretical and experimental optimization of Bessel-like beams for laser manufacture has remained to be investigated. In this paper, we established a theoretical model of the intensity distribution and peak energy density of the Bessel-like beams based on a simplified phase of arc axicon. It was found that the longer propagation length and the lower peak energy density of the Bessel-like beams, contributed to the longer ablation length and higher ablation precision in the silica glass. The ablation length of the optimized Bessel-like beams was at least 1.6 times longer than that of the Bessel beam, which furtherly improved the fabrication efficiency of microdrilling.

Hierarchical microtextures generated by pulsed-laser manufacturing for surface geometry modulation

Enduring surface technologies draw much attention to improving friction performance and prolonging the lifespan of multi-alternative contact pairs. Laser surface texturing is smart to modify effectively the microscopic surface geometries and mechanical performances for the service's improvement of friction pair. This study explored the formation mechanisms and morphology evolution of hierarchical microtextures, with a focus on the thermal field and phase transformation resulting from the laser heating effect on the alloy surface. The controlling variates of laser machining were analyzed considering their influences on microtextures' height and diameter, the pulse numbers are 3 times and 1.7 times of the unit laser power, 81 times and 82.5 times of the unit pulse width. We contributed to the development of laser manufacturing techniques for creating hierarchical microtextures' controllable morphology and smart surface design for tribology engineering and energy management applications.

Development and Proposal of an Institutional Safety Program in the Operation of Laser Systems

Laser radiation can cause undesirable biological effects on living beings; although it is not ionizing, this type of radiation can cause burns to the skin and cornea, even cataracts, depending on the wavelength and intensity of the laser radiation. Due to the wide growth of laser applications in several areas, such as research and development, services, and industry, the occupational risks concerning this non-ionizing radiation have increased considerably worldwide. Several countries have normative documents and regulatory bodies or agencies that approach occupational safety and quality regarding laser application, equipment, and machines. In Brazil, there is a lacking of laser safety documents published by a national regulatory council. Therefore, large technological centers and educational institutions, such as SENAI Institute for Innovation in Laser Manufacturing and Processing Systems (ISI-Joinville) and the Federal Technological University of Paraná (UTFPR), do not have an institutional safety program for laser operations, and to adapt to the most modern international recommendations they look for international documents and models from other institutions. The main objective of this work was to develop and propose an institutional program following Brazilian regulatory documents from the Ministry of Labor and Social Security and the most modern international standard about laser safety from the American National Standards Institute (ANSI-Z 136-1: 2014). The developed safety program was applied to ISI-Joinville, but a model was adapted to be implemented at any research center and university.

Use of lasers in gastrointestinal endoscopy: a review of the literature

Lasers emit highly directional light with consistent wavelengths, and recent studies have demonstrated their successful applications in gastrointestinal endoscopic therapy. Although argon plasma coagulators (APC) became the preferred treatment option due to improved safety profile and lower costs, advancements in laser and optic fiber manufacturing have reignited interest in laser treatment. Different laser wavelengths have distinct features and applications based on their tissue absorption coefficient. Lasers with shorter wavelengths are effectively absorbed by hemoglobin, resulting in a good coagulation effect. Near-infrared lasers have ability to ablate solid tumors, while far-infrared lasers can make precise mucosal incisions without causing peripheral thermal damage. Lasers have proven to be highly applicable to endoscopy devices such as endoscopes, endoscopic ultrasound (EUS), double-balloon enteroscopes (DBE), and endoscopic retrograde cholangiopancreatography (ERCP), making them a potent tool to enhance the effectiveness of endoscopic treatments with minimal adverse events. This review aims to help readers understand the applications and effectiveness of lasers in gastrointestinal endoscopy, with the potential to promote the development and application of laser technology in the medical field.

Spectrally-shaped illumination for improved optical inspection of lateral III-V-semiconductor oxidation.

We report an hyperspectral imaging microscopy system based on a spectrally-shaped illumination and its use to offer an enhanced in-situ inspection of a technological process that is critical in Vertical-Cavity Surface-Emitting Laser (VCSEL) manufacturing, the lateral III-V-semiconductor oxidation (AlOx). The implemented illumination source exploits a digital micromirror device (DMD) to arbitrarily tailor its emission spectrum. When combined to an imager, this source is shown to provide an additional ability to detect minute surface reflectance contrasts on any VCSEL or AlOx-based photonic structure and, in turn, to offer improved in-situ inspection of the oxide aperture shapes and dimensions down to the best-achievable optical resolution. The demonstrated technique is very versatile and could be readily extended to the real-time monitoring of oxidation or other semiconductor technological processes as soon as they rely on a real-time yet accurate measurement of spatio-spectral (reflectance) maps.

Improving TransPRK surgery with Microscan Visum 1100 Hz device for myopia correction

Transepithelial photorefractive keratectomy (TransPRK) with excimer laser “Microscan Visum” (1100 Hz) is a one-stage surgery which does not require changing the sequence of stages for epithelium removal and ablation of cornea stromal part. The “know-how” of Russian excimer laser manufacturers allows to significantly reduce corneal tissue overheating during TransPRK surgery. A new approach to TransPRK surgery consists in simultaneous use of Platoscan program, age nomogram and size of epithelium initial thickness.Purpose: to assess functional outcomes and changes in the corneal epithelium thickness after TransPRK surgery in patients with myopia in the period from 1 month to 1 year.Material and methods. Sixty-six eyes of 33 patients were included in the trial. Average patients’ age was 25.6 ± 6.8 (mean 17–40); 18 men and 15 women. The average spherical component was –2.57 ± 1.54 diopters (from –0.75 to –5.75). The average cylindrical component before surgery was –0.79 ± 0.71 diopters (from 0.00 to –3.5); 45 eyes with mild myopia, 21 eyes with moderate myopia. Epithelium thickness was measured with RTVue-xR Avanti device (Optovue, USA). Calculations were made using Platoscan program and age nomogram (OOO “Opto-systems”, Russia). Assessment of functional outcomes was made using generally accepted standards in refractive surgery.Results. TransPRK has shown its high efficacy, safety, predictability and accuracy in patients with myopia correction. Analysis of OCT findings of the anterior segment using epithelial maps showed that there is no complete restoration of epithelium thickness both in cornea center and in cornea periphery in 7-mm zone by the end of the first month after TransPRK surgery. In one month after TransPRK, epithelium thickness restored by 86.64 % in the center and by 87.99 % in 7-mm zone. Complete restoration of epithelium thickness in the center and in periphery was reached in 6 months. Corneal epithelium thickness in the surgical field increased by 7.9 % both in the center and in periphery in 12 months after the surgery. The ratio of epithelium initial thickness in the center and in periphery to the total cornea thickness before and after the surgery was 10–12 % for the entire study period.

Broadband nanosecond pulse generation modulated by zirconium triselenide nanoflakes

Broadband nonlinear optical modulators are necessary for versatile applications in optical communication, laser radar, laser manufacturing, etc. Here, we report that the zirconium triselenide (ZrSe3) nanoflakes exhibit robust broadband nonlinear optical absorption and can modulate the Nd:YVO4 solid-state laser and erbium-doped ZBLAN fiber laser to deliver stable nanosecond pulse experimentally. The ZrSe3 nanoflakes have been prepared by the liquid phase exfoliation method successfully and exhibit broadband nonlinear optical absorption in the near-infrared and the mid-infrared regime. With the nonlinear absorption performance of the ZrSe3 nanoflakes, stable pulsed operation has been achieved with the output pulse width as short as 344.68 ns around 1 µm from the Q-switched Nd:YVO4 solid-state laser and 599 ns around 2.8 µm from the erbium-doped ZBLAN fiber laser successfully. The experimental results suggest that ZrSe3 nanoflakes can act as an excellent nonlinear optical modulator towards the mid-infrared regime and may make inroads toward developing high-performance broadband optoelectronic devices.

Joint process of laser shock polishing and imprinting for metallic nanostructure fabrication

Most fabrication methods of metallic nanostructures are time-consuming with multi-steps, which are difficult to achieve low-cost batch processing. In this study, joint laser process of laser shock polishing & imprinting (LSPI) is proposed to efficiently fabricate large-area nanostructures on the surface of cheap industrial aluminum foil without any pre-processing step. LSPI tailors the laser parameters of single laser manufacturing equipment to apply laser shock polishing (LSP) to polish the aluminum foil, and then laser shock imprinting (LSI) to obtain nanostructures with high accuracy, integrity and uniformity. This unique characteristic of proposed LSPI is enabled by pre-taking LSP process to improve the yield of following LSI process through significantly decreasing the surface roughness of aluminum foil. LSPI also reduces the aluminum residue inside the silicon mold, which improves the integrity of resultant nanostructure and facilitates the reuse of the mold. The working mechanism of LSPI are also investigated to reveal its fundamental fabrication principle, which may inspire other low-cost and efficient batch fabrication method for metallic nanostructures manufacturing in the future.

Trace photoacoustic SO2 gas sensor in SF6 utilizing a 266 nm UV laser and an acousto-optic power stabilizer.

A sulfur dioxide (SO2) gas sensor based on the photoacoustic spectroscopy technology in a sulfur hexafluoride (SF6) gas matrix was demonstrated for SF6 decomposition components monitoring in the power system. A passive Q-switching laser diode (LD) pumped all-solid-state 266 nm deep-ultraviolet laser was exploited as the laser excitation source. The photoacoustic signal amplitude is linear related to the incident optical power, whereas, a random laser power jitter is inevitable since the immature laser manufacturing technology in UV spectral region. A compact laser power stabilization system was developed for better sensor performance by adopting a photodetector, a custom-made internal closed-loop feedback controller and a Bragg acousto-optic modulator (AOM). The out-power stability of 0.04% was achieved even though the original power stability was 0.41% for ∼ 2 hours. A differential two-resonator photoacoustic cell (PAC) was designed for weak photoacoustic signal detection. The special physical constants of SF6 buffer gas induced a high-Q factor of 85. A detection limit of 140 ppbv was obtained after the optimization, which corresponds to a normalized noise equivalent absorption coefficient of 3.2 × 10-9 cm-1WHz-1/2.

Investigation of the multiple characteristics of the self-mixing effect subject to a single particle.

As a compact interferometry technique, self-mixing interferometry (SMI) is a promising tool for micro particle detection in biochemical analysis and the monitoring of laser manufacturing processing, and currently SMI based micro particle detection is attracting increasing attention. However, unlike the typical displacement or vibration measurement driven by a macro target, only a small amount of literature has targeted the SMI effect induced by a single micro moving particle. In this paper, two numerical models were investigated to describe the characteristics of the signal sparked by individual particle. We compared the measurement results with the two models' simulations in three signal characteristic aspects: the temporal waveform, frequency spectrum, and phase profile. From these results, we established that both amplitude modulation and frequency modulation effects apply under different conditions in the self-mixing process. And for the first time, we analyzed the effect of the laser illumination spot size on the particle-induced SMI signal features with two optical arrangements. When the laser beam size is larger than the particle size, the signal bursts are likely to result from frequency modulation, and vice versa. Our results can improve the capability of SMI technology in particle size discrimination and particle sorting.

Elliptical Supercritical Lens for Shaping Sub-Diffractive Transverse Optical Needle

Supercritical lens can create a sub-diffraction-limited focal spot in the far field, providing a promising route for the realization of label-free super-resolution imaging through the point scanning mechanism. However, all of the reported supercritical lenses have circular shape configurations, and produce isotropic sub-diffraction-limited focal spots in the focal plane. Here, we propose and experientially demonstrate a sub-diffraction transverse optical needle by using an elliptical supercritical lens. Through breaking the circular symmetry and introducing ellipticity to the lens, a uniform sub-diffractive transverse optical needle with lateral length and width of 6λ/NA and 0.45λ/NA, respectively, was successfully created in the focal plane. Further, elliptical sector-shape cutting with an optimized apex angle of 60 degrees can lead to suppressed subsidiary focusing for improved uniformity and condensed field intensity of the transverse optical needle. The demonstration of sub-diffractive transverse optical needle with a high aspect ratio (length to width ratio) of 13:1 may find potential applications in line-scanning microscopy for video-rate label-free super-resolution imaging, and also enable advances in the fields from laser manufacturing to optical manipulation.

Effects of recast layer on fatigue performance of laser-drilled holes in nickel-based superalloy

The effects of the recast layer on the fatigue performance of laser-drilled holes in Ni-based superalloy were experimentally and computationally investigated. It was found that millisecond-laser drilling leads to a recast layer of about 10 μ m , whereas no recast layer was observed in the picosecond-laser drilled hole. The recast layer was confirmed to reveal the Niobium segregation, the Laves phase precipitation and small lattice distortions, resulting in low yield stress. In-situ fatigue test results indicated that the recast layer does not show an obvious influence on the fatigue life of the holed structures in the low-cycle fatigue regime. With the help of the developed cyclic plasticity model, computational analysis verified that the recast layer significantly decreased the stress concentrations around the hole root. The shielding effects improved the fatigue performance of the mismatched material system. The investigations confirm that the millisecond-laser-drilled holes can be used in high-performance turbine blades sofar the recast layer does not dominate the fatigue process, which provides new insights into laser manufacturing.

Artificial Intelligence Empowered Laser: Research Progress of Intelligent Laser Manufacturing Equipment and Technology

Artificial Intelligence Empowered Laser: Research Progress of Intelligent Laser Manufacturing Equipment and Technology

Low-power laser manufacturing of copper tracks on 3D printed geometry using liquid polyimide coating.

Silver nanoparticle photoreduction synthesis by direct laser writing is a process that enables copper micro-track production on very specific polymers. However, some important 3D printing polymers, such as acrylonitrile butadiene styrene (ABS) and acrylates, do not accept this treatment on their surface. This work presents an approach to produce copper microcircuitry on 3D substrates from these materials by using direct laser writing at low power (32 mW CW diode laser). We show that by coating a thin layer of polyimide (PI) on a 3D-printed geometry, followed by a sequence of chemical treatments and low-power laser-induced photoreduction, copper tracks can be produced using silver as catalyst. The surface chemistry of the layer through the different stages of the process is monitored by FTIR and X-ray photoelectron spectroscopy. The copper tracks are selectively grown on the laser-patterned areas by electroless copper deposition, with conductivity (1.2 ± 0.7) × 107 S m-1 and a width as small as 28 μm. The patterns can be written on 3D structures and even inside cavities. The technique is demonstrated by integrating different circuits, including a LED circuit on 3D printed photopolymer acrylate and a perovskite solar cell on an ABS 3D curved geometry.