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Lithium Distribution in Structured Graphite Anodes Investigated by Laser-Induced Breakdown Spectroscopy
摘要： For the development of thick film graphite electrodes, a 3D battery concept is applied, which significantly improves lithium-ion diffusion kinetics, high-rate capability, and cell lifetime and reduces mechanical tensions. Our current research indicates that 3D architectures of anode materials can prevent cells from capacity fading at high C-rates and improve cell lifespan. For the further research and development of 3D battery concepts, it is important to scientifically understand the influence of laser-generated 3D anode architectures on lithium distribution during charging and discharging at elevated C-rates. Laser-induced breakdown spectroscopy (LIBS) is applied post-mortem for quantitatively studying the lithium concentration profiles within the entire structured and unstructured graphite electrodes. Space-resolved LIBS measurements revealed that less lithium-ion content could be detected in structured electrodes at delithiated state in comparison to unstructured electrodes. This result indicates that 3D architectures established on anode electrodes can accelerate the lithium-ion extraction process and reduce the formation of inactive materials during electrochemical cycling. Furthermore, LIBS measurements showed that at high C-rates, lithium-ion concentration is increased along the contour of laser-generated structures indicating enhanced lithium-ion diffusion kinetics for 3D anode materials. This result is correlated with significantly increased capacity retention. Moreover, the lithium-ion distribution profiles provide meaningful information about optimizing the electrode architecture with respect to film thickness, pitch distance, and battery usage scenario.
关键词： laser-induced breakdown spectroscopy,3D battery,lithium-ion battery,ultrafast laser ablation,graphite anode
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Las Vegas, NV, USA (2019.5.28-2019.5.31)] 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Ultrafast Laser Scribe: An Improved Metal and ILD Ablation Process
摘要： Traditional laser scribe which utilizes a nanosecond laser to ablate metal and interlayer dielectric layers (ILD) has been widely adopted by the microelectronics packaging industry as the gold standard for laser scribe processing in die prep singulation. Shrinking device size and thickness are driving increased demand for high die quality or die break strength. Next generation laser scribe tools are being developed to focus on minimizing thermal laser damage by using ultrafast lasers with short pulse widths in the picosecond to femtosecond range. This paper reports a robust ultrafast laser scribe process utilizing a femtosecond ultrafast laser platform developed through ESI and Intel collaboration. This first-of-a-kind equipment and process deliver significant improvement in die break strength and demonstrate a substantial reduction in bulk silicon cracking or voiding as seen in the nanosecond laser scribe heat affected zones (HAZ). Additionally, this ultrafast laser platform offers precise control over beam placement and scribe depth with onboard monitoring capability, key components to delivering a minimally needed scribe depth without sacrificing silicon integrity and processing time. This ultimately leads to a gentle coat-free ablation process that affords a low cost of ownership compare to its peers. Detailed scribe quality characteristics, process controls and overall system manufacturability will be discussed.
关键词： femosecond,ultrafast,laser scribe,ablation,laser grooving
更新于2025-09-12 10:27:22
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Investigation on geometric precision and surface quality of microholes machined by ultrafast laser
摘要： The geometric precision and surface quality of film cooling holes has significant influence on the cooling efficiency and fatigue life of turbine blades. In this paper, the investigation about fabrication process of film cooling holes on the single crystal superalloy DD6 plate specimen by ultrafast laser is carried out. By comparing three different processing paths, minimum roughness of hole wall could be obtained by concentric circular scanning, which was used in the followed-up experiment. The influence of process parameters on the geometric precision and surface quality of microholes was analyzed, and the physical mechanism was examined. The results show that among several process parameters, focus position has the most significant influence on the microholes geometric precision and surface quality, and that the divergent beam (where the focal plane is above the machined surface) can lead to smaller taper, roundness, and surface roughness. In addition, besides a layer of solidified debris adheres to the inner wall at the hole entrance, the microholes machined by ultrafast lasers have no other defects such as a recast layer, microcrack or heat affected zone.
关键词： Geometric precision,Surface quality,Process parameter,Ultrafast laser,Microhole drilling
更新于2025-09-12 10:27:22
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Investigation of interactions between ultrafast laser beams and screen-printed silver nanopaste films
摘要： This study aims to investigate the interaction between ultrafast laser beams and screen-printed silver (Ag) nanopaste ?lms for strain sensors. After single pulse ablation of Ag nanopaste ?lms with a thickness of 4.58 μm, the ablation threshold was approximately 0.2 J/cm2. By increasing single pulse laser ?uences from 0.78 J/cm2 to 1.87 J/cm2, the laser-ablated line widths and depths of Ag nanopaste ?lms were ranging from 22 ± 0.1 μm and 4 ± 0.09 μm to 44.8 ± 1.4 μm and 4.2 ± 0.05 μm, respectively. The sheet resistance of laser-processed Ag nanopaste ?lms was measured by a four-point probe instrument. When the single pulse laser ?uences set from 4.7 mJ/cm2 to 1.97 J/cm2, the measured sheet resistances near the laser-ablated line edge of 0.5 mm were 59.52 ± 0.76 mΩ/sq and 115.83 ± 6.11 mΩ/sq, respectively. The optimal ultrafast laser processing parameters consisting of the areal laser ?uence of 47.4 J/cm2, the laser pulse repetition rate of 300 kHz, the scanning speed of galvanometers of 500 mm/s, and the overlapping rate of laser spots of 96.1% were used to pattern strain sensors with transversal and longitudinal electrode structures on Ag ?lm/glass substrates.
关键词： Sheet resistance,Silver (Ag) nanopaste ?lms,Single pulse ablation,Strain sensor,Ultrafast laser
更新于2025-09-12 10:27:22
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Single-Shot Multi-Stage Damage and Ablation of Silicon by Femtosecond Mid-infrared Laser Pulses
摘要： Although ultrafast laser materials processing has advanced at a breakneck pace over the last two decades, most applications have been developed with laser pulses at near-IR or visible wavelengths. Recent progress in mid-infrared (MiR) femtosecond laser source development may create novel capabilities for material processing. This is because, at high intensities required for such processing, wavelength tuning to longer wavelengths opens the pathway to a special regime of laser-solid interactions. Under these conditions, due to the λ2 scaling, the ponderomotive energy of laser-driven electrons may significantly exceed photon energy, band gap and electron affinity and can dominantly drive absorption, resulting in a paradigm shift in the traditional concepts of ultrafast laser-solid interactions. Irreversible high-intensity ultrafast MIR laser-solid interactions are of primary interest in this connection, but they have not been systematically studied so far. To address this fundamental gap, we performed a detailed experimental investigation of high-intensity ultrafast modifications of silicon by single femtosecond MiR pulses (λ = 2.7–4.2 μm). Ultrafast melting, interaction with silicon-oxide surface layer, and ablation of the oxide and crystal surfaces were ex-situ characterized by scanning electron, atomic-force, and transmission electron microscopy combined with focused ion-beam milling, electron diffractometry, and μ-Raman spectroscopy. Laser induced damage and ablation thresholds were measured as functions of laser wavelength. The traditional theoretical models did not reproduce the wavelength scaling of the damage thresholds. To address the disagreement, we discuss possible novel pathways of energy deposition driven by the ponderomotive energy and field effects characteristic of the MIR wavelength regime.
关键词： ultrafast laser,ablation,silicon,damage threshold,mid-infrared
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Soliton Self-Compression and UV Dispersive Wave Emission in Compact Hollow Capillary Systems
摘要： Soliton dynamics underlie a wide range of phenomena in nonlinear fibre optics. In particular, higher-order solitons in gas-filled hollow-core photonic crystal fibre (HC-PCF) have been applied to self-compression of ultrafast laser pulses [1] and the generation of widely tuneable resonant dispersive waves (RDW) from the vacuum ultraviolet (VUV) to the visible spectral range [2]. We recently demonstrated that by moving to long, large-core hollow capillary fibres (HCF) and shorter driving pulses, these effects can be scaled by up to three orders of magnitude in pulse energy, providing unprecedented peak power in ultrafast VUV pulses as well as a route towards terawatt-scale optical attosecond pulses [3]. Here we show that by further decreasing the initial pulse duration, high-energy soliton dynamics can be obtained in HCF as short as 35 cm.
关键词： Soliton dynamics,ultrafast laser pulses,hollow-core photonic crystal fibre,nonlinear fibre optics,resonant dispersive waves
更新于2025-09-12 10:27:22
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Controlling energy distribution of fast ions and X-ray emission via target reliefs in ultrafast and relativistic laser plasma interaction
摘要： Secondary emission from laser produced plasma is governed by the electron distribution function. Therefore, its control is of utmost importance to steer the emission, e.g., of ultrashort bursts of high energy photons and ions for decisive application. Maximum gain is achieved if the laser light absorption by plasma is also maximized. In our theoretical analysis including comparison to recent experiments, we follow this route and study how the energy is transferred from a short laser pulse to the energy of fast ions and X-rays. We make use of ion and K-a emissions, which respond differently to branches of the electron distribution function when we optimize the laser light absorption via structuring of the target surface. Our investigation comprises laser intensities up to 5 (cid:2) 1020 W/cm2 produced with femtosecond near infrared laser pulses and titanium foil targets of a few micrometer thicknesses. In particular, we reveal an energy relaxation process of hot electrons, which determines the observed laser intensity dependence of secondary emission and points to the bene?t of target surface structuring in different optimization scenarios.
关键词： laser plasma,ultrafast laser,fast ions,electron distribution function,target reliefs,relativistic laser plasma interaction,X-ray emission
更新于2025-09-11 14:15:04
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Reconstruction of coherent anti‐Stokes Raman scattering signals generated by means of laser pulses with asymmetric amplitude and phase
摘要： Time and frequency asymmetries in ultrashort chirped laser fields might appear as a consequence of dispersive propagation, pulse shaping techniques, or generation of auxiliary light pulses needed in nonlinear optics. Here, we try to find an answer to the question of how to solve analytically coherent anti‐Stokes Raman scattering (CARS) under asymmetric conditions of chirped femtosecond laser pulses. The approach breaks in two parts. One for the field amplitudes and the other for the phases. The former revolves around Gaussian dependences that, besides being rather common in ultrashort laser physics, can be arranged and mixed to reproduce spectrally asymmetric laser amplitudes. The latter is limited to field phases with cubic frequency dependence (i.e., second‐order chirp) whose asymmetry is simulated by adding a linear term to the quadratic phase. Both approximations for amplitudes and phases of the three laser pulses are mandatory to guarantee the solution to the complexity posed by the CARS problem. Comparisons with known experimental and numerical results support the validity of the model.
关键词： laser spectroscopy,coherent anti‐Stokes Raman scattering,ultrafast laser physics
更新于2025-09-11 14:15:04
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[IEEE 2019 International Conference on Electronics Packaging (ICEP) - Niigata, Japan (2019.4.17-2019.4.20)] 2019 International Conference on Electronics Packaging (ICEP) - An Investigation of Compound Machining of Ceramic-LPM Package by Ultrafast Laser
摘要： It is well known that ceramic substrates provide excellent electrical insulation and protection from oxidation/ corrosion in addition to idea heat dissipation while allowing heat dissipation through controlled paths, e.g. integrated heat sinks. Low pressure molding (LPM) with polyamide and polyolefin (hot- melt) materials is a process typically used to injection molding for waterproof, to encapsulate and environmentally to protect electronic components. The purpose than epoxy encapsulation is to protect electronic components with finer pitch against moisture, dust dirt and vibration. There is a special need for SiP (System in Package) application utilizing both ceramic substrate and LPM package materials where ceramic serves as mechanical structure and thermal dissipation path and LPM for high density SMT (Surface Mount) package. The research of this paper is to apply nano UV (Ultraviolet) laser to machine the LPM and ceramic substrate (sapphire, Al2O3) and compare the results with nano green laser. The interactions of these two materials with laser are quite different and even conflicting for machining (LPM is ductile and hot-melt while ceramic is brittle), thus proper strategy has to be taken to satisfy needs for both materials. One of the major problem is the re-solidification of LPM material as temperature elevated during laser irradiation. It is necessary to provide a delay time between each laser pulsing. The laser ablation threshold (LAT) of green and UV laser for both materials is also investigated in this paper. The best parameters for processing ceramic substrates are speed 200 mm/s, frequency 95 kHz, delay time 450 ms, when processing LPM speed 700 mm/s, frequency 40 kHz, delay time 250 ms.
关键词： Low Pressure Mold (LPM) compound,laser ablation threshold (LAT),ceramic substrate,ultrafast Laser
更新于2025-09-11 14:15:04
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Femtosecond laser-induced non-centrosymmetric surface microstructures on bulk metallic glass for unidirectional droplet micro-displacement
摘要： Unidirectional droplet motion without energy input has attracted considerable attention in various potential applications. We report on the fabrication of unconventional laser-induced periodic surface structures (LIPSS) for unidirectional droplet micro-displacement by femtosecond laser at large incident angle. In order to overcome the mechanical durability of the existing soft materials such as PDMS for controlling the droplet, Zr-based bulk metallic glass (Zr-BMG) is used to fabricate the typical non-centrosymmetric unconventional LIPSS, which include micro-sized elliptical arc-shaped structures and nano-ripples with the central spatial periodicity of 400 nm. The spots and the grating of unconventional LIPSS on Zr-BMG are fabricated to construct the functional surface structures by femtosecond laser irradiation. The unidirectional micro-displacement of water droplet on Zr-BMG was achieved using functional surface structures. For better understanding the fabrication of unconventional LIPSS, the underlying formation mechanism was revealed by numerical simulations. This work gives a fast, precise and low-cost method to fabricate the non-centrosymmetric surface micro/nano-structures on metal materials for unidirectional droplet motion in microfluidics.
关键词： laser surface structuring,unidirectional droplet motion,LIPSS,bulk metallic glass,Ultrafast laser
更新于2025-09-11 14:15:04