Picosecond Laser Irradiation Research Articles

Quenching high-temperature phase in Cu–Sn alloy system by femtosecond and picosecond laser irradiation

Quenching high-temperature phase in Cu–Sn alloy system by femtosecond and picosecond laser irradiation

Study of damage mechanism on single crystal 4H-SiC surface layer by picosecond laser modification (PLM)

The stable structure, high hardness, and brittleness of single-crystal 4H-SiC present challenges in achieving efficient and damage-free polishing processing. Ultra-short pulsed laser-induced surface modification provides a new solution to enhance the manufacturability of 4H-SiC. This paper aims to investigate the underlying mechanism of the picosecond laser-induced surface structural changes in 4H-SiC and the process of material removal from solid to vapour, elucidating the interaction mechanism between picosecond laser and 4H-SiC. A temperature gradient distribution model for picosecond laser irradiation on 4H-SiC was built to reveal the formation mechanism of subsurface crack damage. The results show that a combination of phase explosion and thermal effects controlled picosecond laser-modified 4H-SiC surfaces deposited spherical SiO2 particles and the process. The study demonstrates that the cracking behaviour in the subsurface of picosecond laser-modified SiC predominantly occurs in the recast region. The fundamental cause of cracking is attributed to the tensile stresses generated by thermal effects and the volumetric changes in the molten material resulting from the overlapping of neighbouring spots in alternating hot–cold cycles. The nanoindentation demonstrated that laser modification can effectively enhance the machinability of SiC. The findings of this study can provide a theoretical basis for efficient non-destructive machining of hard and brittle materials.

Investigation of picosecond laser-induced graphene for dopamine sensing: Influence of laser wavelength on structural and electrochemical performance

This research focuses on a straightforward synthesis method for laser-induced graphene using green (532 nm) and UV (355 nm) picosecond laser irradiation of graphene oxide dispersion. Structural analysis revealed that the laser operating at 355 nm is more favorable to producing a product with a higher content of the restored sp2 network, a higher graphene in-plane crystallite size, a higher concentration of pyrrolic N, and higher values of the optical bandgap. Conversely, the 532 nm laser yielded a sample with higher concentrations of epoxy groups, sp3 defects, and amorphous carbon. Electrochemical analysis for dopamine determination showed potential for both samples as electrode materials. However, the analytical parameters of the sample treated with the 355 nm laser surpass those of the 532 nm laser. It was assumed that the enhanced electrochemical activity results from the presence of pyrrolic N and vacancies in the structure of the sample treated with the 355 nm laser.

Effect of Picosecond Laser Irradiation on the Properties of Nanostructured Zinc Oxide Thin Films

In this article, a picosecond laser source was employed to irradiate the nanostructured ZnO thin film prepared by the sol-gel method. The impact of laser irradiation on the characteristics of a nanostructured ZnO thin film was investigated. Analysis using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy confirmed a significant influence on the structure of the ZnO thin film. As the duration of laser irradiation (the number of laser pulses) increased, there was a remarkable decrease in both the electronic and photoluminescence intensities of the nanostructured film. Tauc's plot indicates a noticeable change in the optical band gaps of the thin film with the increase in irradiation time. The morphological image suggests that the laser irradiation energy induces both degradation and modification of the film surface, consequently causing changes in the structural, absorption, and photoluminescence properties of nanostructured ZnO. The observed effects are attributed to alterations in the crystal structure and size of the nanostructured ZnO film, as confirmed by XRD. The reduction in photoluminescence intensity observed over the laser irradiation times may be a result of potential degradation in the crystalline structure of the nanostructured ZnO film.

The ablation threshold and incubation effect in picosecond laser surface treatment of CFRP

The ablation threshold of carbon fiber is a critical parameter to consider in the laser surface treatment of carbon fiber reinforced polymers (CFRP), as it is necessary to design process parameters based on the threshold fluence to ensure process quality and efficiency. The incubation effect is a key factor influencing the ablation threshold, and a more rational incubation model contributes to a more accurate prediction of the ablation threshold. The conventional incubation model describes the regular decrease of the ablation threshold with an increasing pulse number. However, experimental findings show that the time interval of pulses is also a significant factor affecting the ablation and incubation process. In this study, the conventional incubation model was improved by comprehensively considering the time interval and space interval of pulses, which shows better prediction ability of ablation threshold under different parameter sets. The temperature history of CFRP under picosecond laser irradiation was calculated to support the rationality of the optimized incubation model. In addition, the laser-induced periodic surface structures (LIPSS) and the ablation of carbon fibers and resin were investigated based on the ablation threshold.

Microstructure of Gold Nanoparticles Obtained from a Solution of Hydrochloroauric Acid by Picosecond Laser Irradiation

Microstructure of Gold Nanoparticles Obtained from a Solution of Hydrochloroauric Acid by Picosecond Laser Irradiation

Synergy of Nd:YAG Picosecond Pulsed Laser Irradiation and Electrochemical Anodization in the Formation of TiO2 Nanostructures for the Photocatalytic Degradation of Pesticide Carbofuran

This study proposes a simple and controlled method for producing TiO2 with phase junction, oxygen vacancies, and Ti3+ by combining picosecond pulsed laser irradiation and electrochemical anodization. Ti mesh was pretreated by irradiating with a picosecond pulsed laser technique using an Nd:YAG laser (1064 nm) at two fluencies, 15 J/cm2 and 30 J/cm2. The samples were then subjected to electrochemical anodization to form TiO2 nanotube arrays on the previously laser-treated surface. This study will investigate the possibility of forming TiO2 nanotube arrays on a pre-laser-treated Ti substrate and determine their physicochemical and photocatalytic properties. The samples were characterized by FESEM, XRD, Raman, XPS, and UV-Vis DRS. UV-Vis spectroscopy was used to observe the progress of photocatalytic degradation for all samples, and degradation products were determined using GC-MS. With the synergistic effects of phase junction, oxygen vacancies, and Ti3+, the laser-treated TiO2 with 30 J/cm2 showed a higher photocatalytic degradation rate (85.1%) of the pesticide carbofuran compared to non-laser-treated TiO2 (54.8%), remaining stable during successive degradation cycles, which has promising practical applications.

20µm Micro-LEDs Mass Transfer via Laser-Induced In Situ Nanoparticles Resonance Enhancement.

Ultrafast laser is expected as a promising strategy for micro-LEDs (µ-LEDs) transfer due to its inherent property of suppressing thermal effects. However, its ultrahigh peak power and the unclear transfer mechanism make its transfer quality and efficiency unsatisfactory. Here, the study reports the high-precision mass transfer of 20µm fine-pitch µ-LEDs via in situ nanoparticles (NPs) resonance enhancement in burst mode ultraviolet picosecond laser irradiation. This technique suppresses the thermal melting effect and rapid cooling behavior of plasma by temporal modulation of the burst mode, generating NPs-induced resonance enhancement that accurately and controllable drives a single unit up to tens of thousands of µ-LEDs. The transfer of large µ-LED arrays with more than 180 000 chips is also demonstrated, showing a transfer yield close to 99.9%, a transfer speed of 700 pcs s-1, and a transfer error of <±1.2µm. The transferred µ-LEDs perform excellent optoelectronic properties and enable reliable device operation regardless of complex strain environments, providing a reliable strategy for preparing broader classes of 3D integrated photonics devices.

Microstructure Formations Resulting from Nanosecond and Picosecond Laser Irradiation of a Ti-Based Alloy under Controlled Atmospheric Conditions and Optimization of the Irradiation Process.

This paper presents a study and comparison of surface effects induced by picosecond and nanosecond laser modification of a Ti6Al4V alloy surface under different ambient conditions: air and argon- and nitrogen-rich atmospheres. Detailed surface characterization was performed for all experimental conditions. Damage threshold fluences for picosecond and nanosecond laser irradiation in all three ambient conditions were determined. The observed surface features were a resolidified pool of molten material, craters, hydrodynamic effects and parallel periodic surface structures. Laser-induced periodic surface structures are formed by multi-mode-beam nanosecond laser action and picosecond laser action. Crown-like structures at crater rims are specific features for picosecond Nd:YAG laser action in argon-rich ambient conditions. Elemental analysis of the surfaces indicated nitride compound formation only in the nitrogen-rich ambient conditions. The constituents of the formed plasma were also investigated. Exploring the impact of process control parameters on output responses has been undertaken within the context of laser modification under different environmental conditions. Parametric optimization of the nanosecond laser modification was carried out by implementing an advanced method based on Taguchi's parametric design and multivariate statistical techniques, and optimal settings are proposed for each atmosphere.

Surface-Enhanced Raman Scattering Studies of Au-Ag Bimetallic Nanoparticles with a Tunable Surface Plasmon Resonance Wavelength Synthesized by Picosecond Laser Irradiation

Here, we present a simple and green method of preparing Au-Ag bimetallic nanoparticles (NPs) with a tunable surface plasmon resonance (SPR) wavelength by using picosecond laser irradiation. Au-Ag alloy NPs have been produced by irradiating the solutions containing respective metallic salts in a polyvinyl alcohol (PVA) matrix using a picosecond laser in a single-step process. The SPR wavelength of the Au-Ag bimetallic NPs is observed to be shifted/changed with the Au-Ag concentration and the laser irradiation parameters. The Au-Ag NPs embedded in the PVA matrix are advantageous for Surface-Enhanced Raman scattering (SERS) applications. The estimated enhancement factors (EFs) were observed to vary as a function of conditions of the Au-Ag bimetallic alloy NPs synthesis and also on the concentration of Au at a fixed input fluence of irradiation. The SERS active platforms of Au-Ag bimetallic NPs showed EFs as high as of the order of 108 for Crystal Violet (CV) dye samples at nano molar concentrations. The present study demonstrates a simple, single-step, and green method that fabricates Au-Ag alloy-based nanocomposites suitable for SERS investigations with significantly higher orders of EFs.

Titanium Surface Nanostructuring by Picosecond Laser Irradiation for Surface Improvement of Dental Abutments

Titanium Surface Nanostructuring by Picosecond Laser Irradiation for Surface Improvement of Dental Abutments

Picosecond laser structuring of graphite anodes—Ablation characteristics and process scaling

Laser structuring of graphite anodes substantially improves the electrochemical performance of lithium-ion batteries by facilitating lithium-ion diffusion through the electrode coatings. However, laser structuring is not yet established in industrial battery production due to limited knowledge of its ablation behavior and a low processing rate. This publication addresses these issues with a combination of experimental and theoretical approaches. In a comprehensive process study with picosecond pulsed laser radiation, the influence of various laser parameters on the obtained structure geometries, i.e., the hole diameters and depths, was examined. Wavelengths of 532 and 355 nm combined with pulse bursts and fluences of approximately 10 J cm−2 eventuated in favorable hole geometries with a high aspect ratio. Compared to singlebeam laser structuring, a nearly tenfold reduction in the processing time was achieved by beam splitting with a diffractive optical element without compromising structure geometries or mechanical electrode integrity. The experimental findings were used to model the scalability of electrode laser structuring, revealing the significant influence of the hole pattern and distance on the potential processing rate. Ultrashort pulsed laser powers in the kilowatt regime were found to be necessary to laser-structure electrodes at industrial processing rates resulting in estimated costs of roughly 1.96 $/kWh. The findings support the industrialization of laser electrode structuring for commercial lithium-ion battery production.

Modeling of Electron and Lattice Temperature Distribution Through Lifetime of Plasma Plume

When employing shorter (sub picosecond) laser pulses, in ablation kinetics the features appear which can no longer be described in the context of the conventional thermal model. Meanwhile, the ablation of materials with the aid of ultra-short (sub picosecond) laser pulses is applied for micromechanical processing. Physical mechanisms and theoretical models of laser ablation are discussed. Typical associated phenomena are qualitatively regarded and methods for studying them quantitatively are considered. Calculated results relevant to ablation kinetics for a number of substances are presented and compared with experimental data. Ultra-short laser ablation with two-temperature model was quantitatively investigated. A two-temperature model for the description of transition phenomena in a non-equilibrium electron gas and a lattice under picosecond laser irradiation is proposed. Some characteristics are hard to measure directly at all. That is why the analysis of physical mechanisms involved in the ablation process by ultra-short laser pulses has to be performed on the basis of a theoretical consideration of `indirect' experimental data. For Copper and Nickel metal targets, the two-temperature model calculations explain that the temperature of the electron subsystem increased suddenly and approached a peak value at the end of laser pulse. In addition, the temperature profile of lattice temperature subsystem evolution slowly, and still increasing after the end of laser pulse. A good agreement prevails when a comparison between the present results and published results.

Numerical Simulations of the Acceleration of Fast Protons and of the Excitation of Nuclear Reactions 11B(p, 3a) and 11B(p, n)C11 at the Intensities of Picosecond Laser Radiation in the Range 1018-1019 W/cm2

Results of numerical simulations for acceleration of proton beams at the irradiation of Al target by a superintense laser pulse are presented. There is a good agreement with the experimental data in a broad range of laser intensities from I = 1018 W/cm2 to I = 1019 W/cm2 at the fixed laser pulse duration. The obtained parameters of proton beams were used for calculation of the total yield of a particles and neutrons for the nuclear reactions 11B(p, 3a) and 11B(p, n)C11C at the collisions of proton beams with boron targets. It is shown that the number of a particles escaping boron target and arriving at track detectors is less than 5of the total amount of a particles, because the majority of these particles remain inside the target owing to ionization losses. The derived values of the yield ofparticles’ which arrive at detectors are in good agreement with the experimental data. We also calculate the total yield of neutrons in the reaction 11B(p, n)C11C. It is found that, at the intensity I = 1019 W/cm2 of the picosecond laser pulse, the yield is equal to Nn = 1.4 × 108 , this value is approximately of 3% of the total yield of a particles.

Laser-Induced Graphene in Polyimide for Antenna Applications

Laser-induced graphene (LIG) has gained considerable attention recently due to its unique properties and potential applications. In this study, we investigated using LIG in polyimide (PI) as a material for antenna applications. The LIG-−PI composite material was prepared by a facile picosecond laser (1064 nm) irradiation process, which resulted in a conductive graphene network within the PI matrix. Furthermore, LIG formation was confirmed by Raman spectroscopy and sheet resistance measurements. Finally, a patch antenna from LIG with 2.45 GHz microwaves was simulated, produced and tested. These findings suggest that LIG−PI composites have great potential for use in high-frequency electronic devices and can provide a new avenue for the development of flexible and wearable electronics.

Competition between nonlinear processes excited by picosecond laser pulses in a disodium ditungstate Raman crystal for two excitation polarizations

Two nonlinear processes, namely, two-photon absorption (TPA) and stimulated Raman scattering (SRS) in Na2W2O7 crystal at a wavelength of 523.5 nm, are studied theoretically and experimentally depending on the polarization of the incident picosecond laser radiation. It was found that, due to the anisotropy of the band gap structure, the TPA coefficient at 523.5 nm strongly depends on the pump radiation polarization. For radiation along the c axis with polarization parallel to the a axis, the TPA coefficient was measured to be 1.28 cm GW−1, and no SRS process was registered. However, for polarization parallel to the b axis, no measurable TPA was detected and SRS with a gain of 6.5 cm GW−1 was observed. To the best of our knowledge, this is the first demonstration of the competition of two nonlinear processes in one crystal depending on its orientation.

Precision machining of single crystal diamond cutting tool via picosecond laser irradiation

Due to its high hardness and excellent wear resistance, single crystal diamond has been widely applied in mechanical processing. However, the outstanding hardness leads to great difficulties in the machining of diamond by traditional strategies. In this study, a synchronous feed laser method is developed to realize low damage, high efficiency, and high precision machining of single crystal diamond cutting tools. The disadvantages of traditional direct laser machining, including fullerene residue, bending behavior, and the plasma-shield effect, are well avoided by the good control of the scanning path during the laser fabrication, which enlarges the entrance of the kerf and reduces the air pressure inside the kerf. The synchronous feed laser machining can realize the remarkable increase of kerf depth at high speed, as well as a minimum roughness of ∼147 nm on the cutting surface. It provides a novel, high efficiency, and high precision strategy for the preparation of high quality single crystal diamond tools.

Evolution of structured silicon after picosecond laser irradiation

We prepare the black silicon by directly irradiating crystalline silicon with picosecond laser pulse in atmospheric environment. The grating scanning mode is used in the irradiation process and a regular 20 μm × 20 μm square grating are obtained on the silicon surface. The evolution of surface microstructure with the change of scanning speed and laser pulse energy is preliminarily studied. When the pulse energy is 4.78 μJ and scanning speed is 200 mm/s, picosecond laser can achieve drilling a hole on silicon surface, and the hole will become larger as the the number of pulses increases. In addition, laman spectra is measured and results show picosecond laser processing does not change the crystal phase.

Chemical stability of superhydrophobic stainless steel surfaces realized by laser-texturing and chemical functionalization

The combined adjustment of the topography and of the chemical surface composition of stainless-steel surfaces allows the fabrication of super hydrophobic surfaces with manifold potential applications. However, the factual usability depends in many cases on the chemical stability of the modified surface. The chemical stability in correlation to Hydrogen peroxide (H2O2) of a two-step modified stainless steel surface was studied. For this purpose, the surface was nanostructured by means of ultrashort pulse lasers and then the laser-treated surface was chemically modified by means of a self-assembled monolayer (SAM). This approach enables the specification of nano/microstructure and chemical composition independent of each other. Various hierarchical micro- and nanostructures can be realized by laser texturing of stainless steel surfaces using infrared picosecond laser radiation. The modified surface with different surface topographies was then stored in 50% H2O2-water solution and the contact angle was determined as a function of the exposure time. The H2O2 treatment results in a transition from a super hydrophobic to a super hydrophilic surface where the temporal stability of the super hydrophobic properties is dependent on laser-induced surface topography. Surfaces were produced which exhibited super hydrophobic properties for more than 14 days when stored in 50% H2O2.

Picosecond random Raman lasing in the spectral range of 360–630 nm using powders of potassium, sodium and strontium nitrates

Stimulated Raman scattering (SRS) of picosecond laser radiation at 532 and 355 nm in microcrystalline powders of potassium, sodium, and strontium nitrates has been studied. One anti-Stokes and three Stokes components were generated in all samples when pumping at 532 nm. For the first time to our knowledge, random Raman lasing in the used nitrates has been obtained upon their excitation at 355 nm. In this case, the multifrequency Stokes SRS is also observed in all nitrates. We have analyzed all possible loss channels when ultraviolet radiation is used for excitation of SRS. In general, picosecond random SRS generation has been obtained at 19 spectral lines in the spectral range of 360–630 nm. In all cases, the SRS process is due to the internal symmetric mode of the (NO3)− ion with the frequency shifts of 1050 cm−1 (KNO3), 1069 cm−1 (NaNO3), and 1057 cm−1 (Sr(NO3)2).