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Eruptive Keratoacanthomas in a Red Tattoo After Treatment With a 532-nm Picosecond Laser
摘要： Decorative tattooing continues to be popular, with remorse and request for tattoo removal common in a significant percentage of the tattooed population. Tattoo removal carries complications including inflammatory reactions, infections, and malignancies. Many of these complications are reported to be more frequent in red tattoo ink, conceivably due to the inflammatory nature of the specific components of the red ink particles. Keratoacanthomas (KA) are considered a low-risk form of squamous cell carcinoma (SCC), often associated with injury such as surgery, trauma, and burns. While their association with tattoos has been reported, the eruption of KAs after attempted tattoo removal has not. We report a case of eruptive KAs after tattoo removal using a picosecond laser at an outside facility.
关键词： keratoacanthomas,picosecond laser,red tattoo ink,tattoo removal
更新于2025-09-12 10:27:22
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Investigation of dielectric layers laser ablation mechanism on n-PERT silicon solar cells for (Ni) plating process: Laser impact on surface morphology, composition, electrical properties and metallization quality
摘要： Laser contact opening is a critical step for solar cells manufacturing and needs to be optimized to achieve high efficiencies. In this paper, laser contact opening using a picosecond laser (wavelength 355 nm, pulse duration 10 ps) has been carried out on n-PERT precursors composed of a SiOx/SiOxNy stack on the rear polished side and a SiOxNy layer on the front textured side. By varying peak fluence from 0.130 J/cm2 to 2.159 J/cm2 and spot overlapping, ninety parameters combinations have been tested to open these dielectric layers. Surface morphology characterization, before and after laser ablation, has been realized using Confocal Laser Scanning Microscopy and Scanning Electron Microscopy. Bulk and surface compositions have also been investigated by Energy Dispersive Spectroscopy and X-ray Photoelectron Spectroscopy analysis, respectively. Results have shown the existence of four separated laser impacted areas on the polished side and a related ablation mechanism is suggested. Also, electrical characterization using four probe measurements and calibrated lifetime photoluminescence revealed that electrical properties of the silicon underlying increased when post laser annealing was performed associated with no spot overlapping. Then, nickel electroless deposition has been performed and first characterizations indicate adherence issues and inhomogeneous metallization. Characterization of metallized samples revealed that these observations were closely linked to the non-homogenous surface morphology and composition after laser ablation.
关键词： Ni plating,Surface damages,n-PERT cell,Ablation mechanism,UV-Picosecond laser
更新于2025-09-12 10:27:22
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Electromagnetic field growth triggering super-ponderomotive electron acceleration during multi-picosecond laser-plasma interaction
摘要： The dependence of the mean kinetic energy of laser-accelerated relativistic electrons (REs) on the laser intensity, so-called ponderomotive scaling, explains well the experimental results to date; however, this scaling is no longer applicable to multi-picosecond (multi-ps) laser experiments. Here, the production of REs was experimentally investigated via multi-ps relativistic laser–plasma-interaction (LPI). The lower slope temperature shows little dependence on the pulse duration and is close to the ponderomotive scaling value, while the higher slope temperature appears to be affected by the pulse duration. The higher slope temperature is far beyond the ponderomotive scaling value, which indicates super-ponderomotive REs (SP-REs). Simulation and experimental evidence are provided to indicate that the SP-REs are produced by LPI in an under-critical plasma, where a large quasi-static electromagnetic field grows rapidly after a threshold timing during multi-ps LPI.
关键词： relativistic electrons,electromagnetic field growth,super-ponderomotive acceleration,laser-plasma interaction,multi-picosecond laser
更新于2025-09-11 14:15:04
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The Role of the Surface Nano-Roughness on the Wettability Performance of Microstructured Metallic Surface Using Direct Laser Interference Patterning
摘要： Superhydrophobic natural surfaces usually have multiple levels of structure hierarchy, particularly microstructures covered with nano-roughness. The multi-scale nature of such a surface reduces the wetting of water and oils, and supports self-cleaning properties. In this work, in order to broaden our understanding of the wetting properties of technical surfaces, biomimetic surface patterns were fabricated on stainless steel with single and multi-scale periodic structures using direct laser interference patterning (DLIP). Micropillars with a spatial period of 5.5 μm and a structural depth of 4.2 μm were fabricated and covered by a sub-micro roughness by using ultrashort laser pulses, thus obtaining a hierarchical geometry. In order to distinguish the influence of the different features on the wettability behavior, a nanosecond laser source was used to melt the nano-roughness, and thus to obtain single-scale patterns. Then, a systematic comparison between the single- and multi-scale structures was performed. Although, the treated surfaces showed hydrophilic behavior directly after the laser treatment, over time they reached a steady-state hydrophobic condition. However, the multi-scale structured metal showed a contact angle 31° higher than the single-scale geometry when the steady-state conditions were reached. Furthermore, the impact of the surface chemistry was investigated by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) analyses. Finally, a hydrophobizing agent was applied to the laser treated samples in order to further enhance the water contact angles and to determine the pure contribution of the surface topography. In the latter case, the multi-scale periodic microstructures reached static contact angles of 152° ± 2° and a contact angle hysteresis of only 4° ± 2°, while the single-scale structures did not show superhydrophobic behavior. These results definitely suggest that multi-scale DLIP structures in conjunction with a surface chemistry modification can promote a superhydrophobic regime.
关键词： multi-scale microstructures,wettability transition,nanosecond and picosecond laser pulses,direct laser interference patterning
更新于2025-09-11 14:15:04
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Metal ablation study with a 10 picosecond laser under low and median fluence
摘要： Single shot 10 ps laser ablation on aluminium and gold at a wavelength of 1064 nm under low and median laser fluence was studied theoretically and experimentally. Simulations have been performed by using an optimized two temperature model. It is revealed that electron-phonon coupling ability of the target metal affected both the ablation depth and target metal’s morphology. Under low fluence, melting could well be the relevant ablation mechanism. With laser fluence rising, vaporization or phase explosion happens thereafter, depending on material’s electron-phonon coupling ability.
关键词： Metals and alloys,Picosecond laser processing,Modeling of laser ablation
更新于2025-09-11 14:15:04
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One-step P2 scribing of organometal halide perovskite solar cells by picosecond laser of visible wavelength
摘要： Perovskite solar cells (PSC) have attracted attention by its unprecedented rise in device efficiency. However, the PSCs were mostly tested for the unit cell of small area, and it is important to upscale to solar modules. Laser scribing has great potential to this end. However, the key challenge identified in one-step P2 laser scribing is to remove film stack including the hole block layer (HBL) without damaging transparent conducting oxide (TCO) based bottom contact and thus to provide interconnecting paths with minimized contact resistance. In this study, we evaluate one-step P2 scribing performance of picosecond laser of 532 nm wavelength for mesoscopic perovskite architecture with the c-TiO2 as the HBL and fluorine doped tin oxide (FTO) as bottom contact. Despite anticipated challenge of low absorption selectivity, c-TiO2 layer could be efficiently removed without FTO damage over wide processing window enabling a self-terminating mechanism. Detailed parametric studies elucidate relevant scribing mechanisms such as layer-by-layer ablation mechanism or lift-off mechanism depending laser illumination direction. It is also revealed that the removal of c-TiO2 is triggered by ablation of upper layers, in particular, the mesoporous TiO2. Module level test is under way in conjunction with investigation of further scribing mechanisms.
关键词： picosecond laser,P2 scribing,laser scribing,Perovskite thin film solar cell
更新于2025-09-11 14:15:04
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Crafting Interior Holes on Chemically Strengthened Thin Glass Based on Ultrafast Laser Ablation and Thermo-Shock Crack Propagations
摘要： To prevent glass cracking from external mechanical damages, chemically strengthened glass is usually employed. The cutting of strengthened glass becomes critical due to their residual tensile stress induced in the inner core of the display unit of mobile communication and computational devices. This method integrates picosecond laser ablation with quenching induced thermo-shock for accomplishing such a task. Essential analyses are performed based on fracture mechanics and finite element method to provide the scientific basis of such an approach. Experimental results indicate that with a proper temperature control, the proposed method could achieve successful separations for various enclosed shapes with the associated surface roughness satisfying the requirement.
关键词： thermo-shock,Glass,picosecond laser ablation,Packaging
更新于2025-09-11 14:15:04
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Versatile high power pulse-laser source for pico- and nanosecond optical pulses
摘要： This paper presents a pulse-laser source for the generation of ps and ns laser pulses with more than 50 W peak output power. The final stages of the drivers use GaN transistors and are capable of switching currents of 0.8 A with 200 ps minimum pulse width and 50 A with 3 ns minimum pulse width. The pulses can be externally triggered by ECL logic. Both single-pulse and pulse train modes are possible.
关键词： fast current driver,GaN HEMT,optical pulse gating,Picosecond laser source
更新于2025-09-11 14:15:04