Search Results (59)

Hydrogenated tetrahedral amorphous carbon (ta-C:H) thin films were modified using 266 nm picosecond laser pulses to investigate structural transformations at low and moderate fluences. Nitrogen-doped hydrogenated tetrahedral amorphous carbon layers 20–40 nm thick were deposited on silicon (Si) and silicon dioxide on silicon (SiO₂/Si) substrates and irradiated with picosecond pulses at 0.5–1.6 J cm⁻² using a raster-scanned beam. Structural changes in morphology, composition, and bonding were evaluated via optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Even below 1.0 J cm⁻², localized color shifts and slight swelling indicated early structural rearrangements without significant material removal. Above 1.0–1.2 J cm⁻², the films were largely ablated, although a persistent 3–6 nm carbon layer remained on both substrate types. XPS showed an increase in sp²-bonded carbon by roughly 15%–20% in optimally modified regions, and Raman spectroscopy revealed defect-activated D-bands and the formation of multilayer defective graphene or reduced-graphene-oxide-like flakes at ablation boundaries. These results indicate that picosecond ultraviolet irradiation enables controllable graphitization and thinning of ta-C:H films while maintaining uniform processing over centimeter-scale areas, providing a route to thin, conductive, partially graphitized carbon coatings for optical and electronic applications. Full article

This work demonstrates a three-step method for the synthesis and production of submicron spherical gold particles using laser ablation in liquid (LAL), laser-induced fragmentation in liquid (LFL), laser-induced nanochain formation, and laser melting in liquid (LML). The nanoparticles were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), and UV–visible spectroscopy. In the first stage, spherical gold nanoparticles with a size of 20 nm were obtained using LAL and LFL. Subsequent irradiation of gold nanoparticle colloids with radiation at a wavelength of 532 nm leads to the formation of gold nanochains. Irradiation of nanochain colloids with radiation at a wavelength of 1064 nm leads to the formation of large spherical gold particles with a size of 50 to 200 nm. The formation of submicron gold particles upon irradiation of 2 mL of colloid occurs within the first minutes of irradiation and is complete after 480,000 laser pulses. Increasing the laser pulse energy leads to the formation of larger particles; after exceeding the threshold energy (321 mJ/cm²), fragmentation is observed. Increasing the concentration of nanoparticles in the initial colloid up to 150 μg/mL leads to a linear increase in the size of submicron nanoparticles. The use of picosecond pulses for irradiating nanochains demonstrates the formation of the largest particles (200 nm) compared to nanosecond pulses, which may be due to the effect of local surface melting. The described technique opens the possibility of synthesizing stable gold nanoparticles over a wide range of sizes, from a few to hundreds of nanometers, without the use of chemical reagents. Full article

Gold nanoparticles (AuNPs) synthesized via picosecond pulsed laser ablation were investigated as enhancers of methylene blue (MB)-mediated photodynamic therapy (PDT) against Escherichia coli. AuNPs produced at 532 and 1064 nm with frequencies of 20–50 kHz showed frequency- and size-dependent effects, with 50 kHz yielding the highest particle concentrations and smaller particles enhancing reactive oxygen species (ROS) generation. UV-Vis and fluorescence spectroscopy confirmed nanoparticle formation and plasmonic properties consistent with TEM measurements. Photobleaching assays demonstrated that AuNPs significantly increased MB singlet oxygen generation, while the efflux pump inhibitor INF-55 further amplified bacterial killing without altering net ROS yield. In vitro assays revealed that INF-55 combined with MB/AuNPs achieved ~59% higher bacterial deactivation compared to MB/AuNPs alone. Molecular docking confirmed stronger binding of INF-55 to the AcrB efflux pump (−9.1 kcal/mol) than MB, supporting its role as a competitive inhibitor that promotes intracellular MB retention. These findings establish a dual-action PDT strategy in which AuNPs enhance ROS production and INF-55 augments antibacterial efficacy via efflux pump inhibition. Together, this platform provides a proof of concept for future translation to biofilm- and tissue-based infection models, and potentially to localized clinical applications such as prosthetic joint, catheter-associated, or chronic wound infections where conventional sterilization or systemic antibiotics are insufficient. Full article

Roll-to-roll production of thin organic and large-area electronic (TOLAE) devices often involves a two-step process per functional layer: a continuous, un-pattered deposition of the film and subsequent structuring process, such as laser ablation. Thin-film organic devices should be protected using ultra-barrier films. To perform laser ablation of functional layers on top of such barrier films, in particular that of transparent electrodes, highly selective laser ablation is required to completely remove the layers without damaging the thin-film barrier layers underneath. When targeting highly selective laser ablation of indium tin oxide (ITO) on top of silicon nitride (SiN) barrier layers with a 1064 nm picosecond or 1030 nm femtosecond laser, we observed the emergence of visible large-scale patterns due to local variations in ablation quality. Our investigations using a very sensitive Raman spectroscopy setup show that the observed ablation variations stem from subtle differences in optical path length within the heat-stabilized plastic substrates. These variations are likely caused by minute, localized changes in the refractive index, introduced during the bi-axial stretching process used in film fabrication. Depending on the optical path length, these variations lead to either constructive or destructive interference between the incoming laser beam and the light reflected from the back surface of the substrate. By performing laser ablation under an angle such that the reflected and incoming laser beam do not spatially overlap, highly selective uniform laser ablation can be performed, even for two stacked optically transparent layers. Full article

This study systematically investigates the influence of laser pulse duration on cutting efficiency, heat-affected-zone (HAZ) formation, and mechanical integrity during carbon fiber-reinforced polymer (CFRP) laser cutting. Three distinct pulse-width lasers—picosecond, nanosecond, and quasi-continuous-wave (QCW)—are compared. Results show that pulse duration governs material removal mechanisms and HAZ extent: the nanosecond laser achieves the smallest HAZ and minimal porosity; the picosecond laser exhibits limited thermal accumulation due to low average power; and the QCW laser induces the largest HAZ (11.6 times that of the nanosecond laser) and significant porosity. Cutting efficiency scales inversely with pulse width, with single-hole processing times of 480.4 s for picosecond-laser cutting, 76.8 s for nanosecond-laser cutting, and 4.028 s for QCW-laser cutting, reflecting a transition from thermal ablation to mechanical spallation. Mechanical testing reveals that while tensile and flexural strengths vary by less than 5% across laser types, damage morphology and failure modes differ significantly. In situ digital image correlation (DIC) and 3D CT imaging show that longitudinal plies fail via fiber pull-out, whereas transverse plies fail via interfacial debonding. QCW-laser-cut specimens exhibit more uniform strain distribution and higher damage tolerance. An optimized process parameter is proposed: nanosecond-laser cutting at 200 W and 20 kHz achieves a HAZ of less than 50 µm and a cutting time of less than 80 s, offering the best balance between efficiency and quality. Full article

4H-SiC wafers usually require polishing treatment after slicing to improve the surface quality. However, traditional polishing processes have problems such as low removal efficiency and easy surface damage, which affect the reliability of electronic devices. In this paper, picosecond laser polishing technology is used to study the 4H-SiC wafers after slicing. Numerical models of single-pulse ablation and moving heat source polishing were established to reveal the interaction mechanism between laser and material, including the dynamic evolution of free electron density and the remarkable spatiotemporal non-equilibrium heat transfer characteristics of the electron–lattice system. The sliced 4H-SiC surface with a roughness of 2265 nm was polished by a 1064 nm picosecond laser, and the influence of laser power and scanning speed on the surface quality was systematically studied. By collaboratively optimizing the polishing power and speed, the surface roughness of the sample can be significantly reduced to 207.33 nm (a decrease of 90.85%). The research results indicate that an ultrafast laser is suitable for the pretreatment process of sliced silicon carbide wafers, laying a foundation for further research in the future. This research has a certain research significance for promoting the development of ultrafast laser polishing technology for single crystal silicon carbide wafers and improving the performance and reliability of semiconductor devices. Full article

Glass-based microfluidic devices are essential for applications such as diagnostics and drug discovery, which utilize their optical clarity and chemical stability. This review systematically analyzes pulsed laser micromachining as a transformative technique for fabricating glass-based microfluidic devices, addressing the limitations of conventional methods. By examining three pulse regimes—long (≥nanosecond), short (picosecond), and ultrashort (femtosecond)—this study evaluates how laser parameters (fluence, scanning speed, pulse duration, repetition rate, wavelength) and glass properties influence ablation efficiency and quality. A higher fluence improves the material ablation efficiency across all the regimes but poses risks of thermal damage or plasma shielding in ultrashort pulses. Optimizing the scanning speed balances the depth and the surface quality, with slower speeds enhancing the channel depth but requiring heat accumulation mitigation. Shorter pulses (femtosecond regime) achieve greater precision (feature resolution) and minimal heat-affected zones through nonlinear absorption, while long pulses enable rapid deep-channel fabrication but with increased thermal stress. Elevating the repetition rate improves the material ablation rates but reduces the surface quality. The influence of wavelength on efficiency and quality varies across the three pulse regimes. Material selection is critical to outcomes and potential applications: fused silica demonstrates a superior surface quality due to low thermal expansion, while soda–lime glass provides cost-effective prototyping. The review emphasizes the advantages of laser micromachining and the benefits of a wide range of applications. Future directions should focus on optimizing the process parameters to improve the efficiency and quality of the produced devices at a lower cost to expand their uses in biomedical, environmental, and quantum applications. Full article

Recent advances in glass-ceramics research have expanded their applications in astronomy, optoelectronics, and laser systems. However, precision cutting technology remains challenging. This study optimized picosecond laser processing parameters for 600 nm-thick glass-ceramics, revealing critical influences of point spacing, laser energy, and pulse number. Atomic force microscopy showed that 1 µm processing spacing enabled uniform ablation grooves with optimal roughness. Two-pulse configurations achieved the most consistent surface improvement. At 12.5 W incident power, samples exhibited minimized average roughness (219 nm) with localized values reaching 208 nm, alongside 1.2 N breaking stress. Full article

This study investigated the effects of water-based and underwater assistance methods on the quality of picosecond laser-drilled microholes in silicon nitride ceramics, analyzing the influence of laser power variations in air and aqueous environments on entrance/exit diameters, taper angles, internal wall morphology, surface roughness, and oxygen content. Water-based assistance involved submerging the workpiece’s lower surface while keeping the upper surface in the air, whereas underwater processing involved fully immersing the specimen. The experimental results demonstrated that both aqueous environments effectively improved microhole quality compared to air processing. The water-assisted methods significantly enhanced the entrance/exit morphology by reducing ablation traces and slag deposits. The aqueous medium increased the entrance/exit diameters while decreasing the taper angles and effectively removing debris, thereby reducing internal wall roughness. Underwater processing achieved lower roughness at the hole entrances and middle sections compared to water-based assistance. Both water-assisted methods produced superior internal wall morphology to air processing, with comparable performance. These findings provide valuable references for optimizing water-assisted picosecond laser drilling processes. Full article

WC–Co cemented carbide has been widely used as machining tool material due to its good mechanical properties. Grinding is an important process in the manufacture of cemented carbide tools. When grinding tools, there are problems such as excessive grinding force, small chip space, and poor lubrication and cooling performance, which in turn contribute to surface defects such as burrs, burns, and even edge damage such as edge chipping. These problems constrain the use of carbide tools, so that the cutting force is unstable and the machining surface quality is poor when the tool is in service. In this paper, straight-line and wavy-texture patterns were designed and formed on the surface of WC–Co tools using a picosecond laser. Grinding experiments were conducted on the ablated tool using a resin-bonded diamond wheel, and surface morphology, roughness, grinding force, and cutting edge quality were evaluated. Finally, turning experiments were conducted to compare the cutting performance of the tools after conventional and laser-assisted grinding. The experimental results showed that the tools with wavy texture showed superior surface and cutting edge quality, with 53.7% and 51.2% reduction in normal and tangential grinding forces, respectively, and 66.6% maximum reduction in edge chipping for the wavy textured tools. Therefore, this study not only reveals the advantages of laser-assisted grinding in machining WC–Co cutting tools, but also provides a valuable theoretical basis for realizing high-efficiency and low-loss tool machining. Full article

In this work, atmospheric pulsed laser deposition was used to prepare photosensitive elements. This technology is a practical and relatively inexpensive way of obtaining highly porous nanostructures composed of nanoparticles or nanoaggregates characterized by a large surface-to-volume ratio. Samples were produced via laser nanosecond or picosecond laser ablation of pure ZnO or mixed ZnO-TiO₂ targets on quartz substrates with pre-deposited gold electrodes. The structure, morphology, optical, and electrical properties of the nanostructures obtained were studied regarding the sample composition and laser ablation regime applied. The ablation of a mixed ZnO-TiO₂ target led to the fabrication of composite samples consisting of ZnO and Zn₂TiO₄ nanoparticles. The electrical properties of pure and composite samples were studied under exposure to UV light irradiation. It was found that the photosensitive properties of the samples depended on the ablation regime applied. The dark current measured for the nanosecond-deposited samples was a few nA, which was an order of magnitude larger compared to the picosecond-deposited samples. The value of the photogenerated current of the nanosecond-deposited samples was 10³-times higher than that of the picosecond-deposited samples. This is due to the lower absorption of the picosecond-deposited samples, as well as to the presence of defect-related radiative recombination in the picosecond-deposited samples, which limits the photocurrent rise. The estimated rise and decay times were longer for the composite samples independently of the deposition regime applied. Full article

Ultrafast lasers, characterized by femtosecond and picosecond pulse durations, have revolutionized material processing due to their high energy density and minimal thermal diffusion, and have played a transformative role in precision manufacturing. This review first traces the progression from early ruby lasers to modern titanium–sapphire lasers, highlighting breakthroughs like Kerr-lens mode-locking and chirped pulse amplification. It also examines the interaction mechanisms between ultrafast pulses and various materials, including metals, dielectrics, and semiconductors. Applications of ultrafast lasers in microstructure processing techniques are detailed, such as drilling, cutting, surface ablation, and nano welding, demonstrating the versatility and precision of the technology. Additionally, it covers femtosecond laser direct writing for optical waveguides and the significant advancements in imaging and precision measurement. This review concludes by discussing potential future advancements and industrial applications of ultrafast lasers. Full article

K9 glass is a classical transparent material widely used in high-power optical systems due to its high-temperature resistance. However, the precision machining of K9 glass is difficult. The laser processing method, characterized by being non-contact, having a small heat-affected zone, and having high processing precision, is commonly employed for processing intricate structures. In this study, the vector diffraction model is employed to simulate the internal electric field inside the material when focused by objective lenses with varying numerical apertures. Furthermore, the temperature field is simulated. The simulation considered the nonlinear absorption of the material, the stretching of the focal dot due to spherical aberration, and the energy loss of the laser during the focusing process. The experiment indicated that the ablated area consists of numerous small, ablated dots and that multiple ablated areas emerged under an NA of 0.6. This study can provide valuable references for the research of the interaction between lasers and glass materials. Full article

The cutting of thick glass is extensively employed in aerospace, optical, and other fields. Although ultrafast laser Bessel beams are heavily used for glass cutting, the cutting thickness and cutting quality need to be further improved. In this research, the high-quality cutting of thick glass was realized for the first time using ultrafast laser perforation assisted by CO₂ laser separation. Initially, an infrared picosecond laser Bessel beam was employed to ablate the soda-lime glass and generate a perforated structure. Subsequently, a CO₂ laser was employed to induce crack propagation along the path of the perforated structure, resulting in the separation of the glass. This study investigates the influence of hole spacing, pulse energy, and the defocusing distance of the picosecond laser Bessel beam on the average surface roughness of the glass sample cutting surface. The optimal combination of cutting parameters for 6 mm thick glass results in a minimum surface roughness of 343 nm in the cross-section. Full article

We present a two-step physical method for the fabrication of composite nanoparticle-based nanostructures. The proposed method is based on the pulsed laser deposition (PLD) technique performed sequentially in vacuum and in air. As a first step, thin-alloyed films of iron with noble metal were deposited by PLD in vacuum. The films were prepared by ablation of a mosaic target formed by equal iron and gold sectors. As a second step, the as-prepared alloyed films were ablated in air at atmospheric pressure as the laser beam scanned their surface. Two sets of experiments were performed in the second step, namely, by applying nanosecond (ns) and picosecond (ps) laser pulses for ablation. The structure, microstructure, morphology, and optical properties of the samples obtained were studied with respect to the laser ablation regime applied. The implementation of the ablation process in open air resulted in the formation of nanoparticle and/or nanoparticle aggregates in the plasma plume regardless of the ablation regime applied. These nanoparticles and/or nanoaggregates deposited on the substrate formed a complex porous structure. It was found that ablating FeAu films in air by ns pulses resulted in the fabrication of alloyed nanoparticles, while ablation by ps laser pulses results in separation of the metals in the alloy and further oxidation of Fe. In the latter case, the as-deposited structures also contain core–shell type nanoparticles, with the shell consisting of Fe-oxide phase. The obtained structures, regardless of the ablation regime applied, demonstrate a red-shifted plasmon resonance with respect to the plasmon resonance of pure Au nanoparticles. Full article