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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) - Dark Pulses in a Long Ring Laser
摘要： A capacitive-piezoelectric transducer combines capacitive and piezoelectric mechanisms to achieve a combination of electromechanical coupling and Q higher than otherwise attainable by either mechanism separately, has allowed demonstration of a 1.2-GHz contour-mode aluminum nitride (AlN) ring resonator with Q > 3000 on par with the highest measured d31-transduced AlN-only piezoelectric resonators past 1 GHz, and a 50-MHz disk array with an even higher Q > 12 000. Here, the key innovation is to separate the piezoelectric resonator from its metal electrodes by tiny gaps to eliminate metal material and metal-to-piezoelectric interface losses thought to limit thin-film piezoelectric resonator Q, while also maintaining high electric field strength to preserve a strong piezoelectric effect. While Q increases, electromechanical coupling decreases, but the k2 · Q product can still increase overall. More importantly, use of the capacitive-piezo transducer allows a designer to trade electromechanical coupling for Q, providing a very useful method to tailor Q and coupling for narrowband radio frequency (RF) channel-selecting filters for which Q trumps coupling. This capacitive-piezo transducer concept does not require dc-bias voltages and allows for much thicker electrodes that reduce series resistance without mass loading the resonant structure. The latter is especially important as resonators and their supports continue to scale toward even higher frequencies.
关键词： electromechanical coupling,oscillator,Micromechanical resonator,self-alignment,small gap,aluminum nitride,equivalent circuit,quality factor,filter
更新于2025-09-19 17:13:59
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Influence of Magnesium on Spatter Behavior in Laser Deep Penetration Welding of Aluminum Alloys
摘要： The quality of welds, as well as the necessity of post-processing, is challenged by spatter generation during the laser keyhole welding process. In this study, the influence of the magnesium content on spatter behavior is studied for three aluminum alloys (Al99.5, AlMg3, and AlMg5). A synchronized dual high-speed camera system is used to observe the spatter behavior and to reconstruct 3D spatter trajectories as well as determine the characteristics of spatter velocity, flight path angle, and approximate spatter size. The mean spatter velocities and flight path angles of the welding experiments with the three alloys were in welding direction between 4.1 m/s and 4.6 m/s and 44.8°, respectively. Furthermore, the AlMg alloys show excessive spatter behavior with spray events of more than 50 spatters at a time, and less frequently spatter explosions. Spatter spray events show a character similar to spatter explosions. Volumetric evaporation is proposed as effecting these events. In contrast, and resulting from a different mechanism, pure aluminum (Al99.5) shows group ejection events with at least 10 spatters at a time. In this study, there are no correlations between spatter velocities and flight path angles, nor between velocities and approximate spatter sizes.
关键词： high-speed imaging,keyhole welding,aluminum alloy,welding,laser welding,spatter
更新于2025-09-19 17:13:59
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Charge-Transfer Character in Excimers of Perylenediimides Self-Assembled on Anodic Aluminum Oxide Membrane Walls
摘要： Chromophore aggregation strongly impacts the efficiency of organic photovoltaics (OPVs). Perylene-3,4:9,10-bis(dicarboximide) (PDI)-based electron acceptors have been shown to be excellent alternatives to fullerenes in OPVs, provided their supramolecular assemblies do not form excimers. In order to study this phenomenon in a controlled fashion, we have prepared two PDI derivatives that were incorporated into an anodic aluminum oxide (AAO) membrane. In one system, the PDI molecule has an n-propyl silatrane attached to one of its imide nitrogens, while a 12-tricosanyl group is attached to the other imide nitrogen. The silatrane reacts with the AAO surface to covalently bind the PDI. The other PDI has 12-tricosanyl groups on both imide nitrogens, which intercalate with n-octadecylsilane chains covalently bound to an AAO membrane. Since aluminum oxide is a wide bandgap semiconductor, photoexcitation of PDI does not result in charge injection into the AAO membrane; thus, the intrinsic electronic properties of the aggregated PDI molecules within the membrane can be studied. Both PDI derivatives form excimers upon photoexcitation with and without solvent in the AAO membrane pores which display increasing charge transfer character with increasing solvent polarity. Since the AAO membrane allows for any choice of solvent to be infiltrated into its pores, the PDI photophysics can be modulated over an arbitrary range of solvent polarities, irrespective of whether PDI is soluble in a particular solvent. The results presented here show how to tune the intermolecular interactions of PDI and related rylene dyes attached to walls of the AAO pores to understand the intermediate regime between solution and the solid state.
关键词： Excimers,Anodic aluminum oxide membrane,Perylene-3,4:9,10-bis(dicarboximide),Chromophore aggregation,Charge transfer character,Organic photovoltaics
更新于2025-09-19 17:13:59
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Laser Annealing of P and Al Implanted 4H-SiC Epitaxial Layers
摘要： This work describes the development of a new method for ion implantation induced crystal damage recovery using multiple XeCl (308 nm) laser pulses with a duration of 30 ns. Experimental activity was carried on single phosphorus (P) as well as double phosphorus and aluminum (Al) implanted 4H-SiC epitaxial layers. Samples were then characterized through micro-Raman spectroscopy, Photoluminescence (PL) and Transmission Electron Microscopy (TEM) and results were compared with those coming from P implanted thermally annealed samples at 1650–1700–1750 °C for 30 min. The activity outcome shows that laser annealing allows to achieve full crystal recovery in the energy density range between 0.50 and 0.60 J/cm2. Moreover, laser treated crystal shows an almost stress-free lattice with respect to thermally annealed samples that are characterized by high point and extended defects concentration. Laser annealing process, instead, allows to strongly reduce carbon vacancy (VC) concentration in the implanted area and to avoid intra-bandgap carrier recombination centres. Implanted area was almost preserved, except for some surface oxidation processes due to oxygen leakage inside the testing chamber. However, the results of this experimental activity gives way to laser annealing process viability for damage recovery and dopant activation inside the implanted area.
关键词： ion implantation,phosphorus,point defects,laser annealing,photoluminescence,aluminum,TEM,Metal Oxide Semiconductor Field Effect Transistor (MOSFET),SiC,Raman
更新于2025-09-19 17:13:59
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Fabrication of gold nanorod arrays on a cylindrical surface of optical fibers by using in-situ electrodeposition
摘要： Optical fiber is an excellent light-coupled substrate, which has the characteristics of large a length-diameter ratio with a cylindrical surface. Recently, various methods have been reported in order to improve the ability of local optical fields. In particular, methods aimed to address the efficient coupling and optical resonances by modifying metal nanostructures on the light-coupled substrate have been developed. However, existing methods are largely applicable to planar or tip substrates, and it remains a significant challenge to prepare metal nanostructures on a cylindrical substrate. In this study, we proposed a novel strategy to fabricate gold nanorods arrays (AuNRs) by electrodepositing them in anodized aluminum oxide (AAO) templates on the cylindrical surface of optical fibers. Briefly, AAO templates were prepared in-situ by using a constant current density secondary oxidation method on the cylindrical surface of optical fibers, and then the AuNRs were in-situ deposited in the AAO templates by electrodeposition. The features of the AuNRs such as diameter, nanorod pitch, and height could be easily regulated by adjusting the parameters of electrodeposition and the anode oxidation. The SEM images demonstrates that AuNRs exhibit a satisfactory consistency with a uniform diameter and favorable self-supporting properties. The relationships between the current density, pore diameter and pore distribution were explored, combined with the voltage-time curve during anodic oxidation. Furthermore, the surface plasmon resonance (SPR) optical properties of the AuNRs on the cylindrical surface were analyzed using the Finite-difference Time-domain Algorithm (FDTD) method. Results suggest that this alternative in-situ electrodeposition strategy has the potentials to be applied to SPR optical fiber sensing.
关键词： Gold nanorods arrays,Finite-difference time-domain algorithm,In-situ electrodeposition,Cylindrical surface of optical fibers,Anodized aluminum oxide templates
更新于2025-09-19 17:13:59
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Observation of keyhole and melt pool dynamics in laser welding of Al alloy by x-ray phase-contrast method
摘要： Aluminum alloy is a lightweight material frequently used for automotives parts, batteries, airplanes, etc. to reduce greenhouse gas emissions. A highly efficient and stable laser welding method has long been sought for Al alloy because of its poor weldability due to its high heat conductivity and high reflectivity of 1 μm wavelength laser light. Because welding phenomena and defect formation mechanism are still not properly understood due to their complexity, this research aims to investigate the laser welding phenomena of Al alloy. To understand the weld pool and keyhole dynamics during welding, the weld pool was observed with a high-speed camera and X-ray phase-contrast method. The keyhole behavior and solid-liquid interface during laser welding for A1050 can be observed more clearly than in X-ray absorption-contrast method. At a lower welding speed (0.5 m/min), frequent intensive keyhole expansion and high porosity could be observed. Although high porosity could be observed at a higher welding speed (1 m/min), keyhole expansion was barely observed. It is thought that at a low welding speed, intensive evaporation at keyhole bottom leads to unstable keyhole behavior due to high heat input, and as a result, high porosity is formed due to be intake of air into the keyhole. The effect of fan usage was evaluated. In the case without a fan, intensive keyhole expansion was observed frequently. It is supposed that the laser partly interacted with plume, which led to a sudden evaporation due to laser scattering. It was observed that a bubble from the keyhole bottom moved around the keyhole at a high speed, and the bubble was trapped at a solid-liquid interface. Then the bubble grew by absorbing other small bubbles in a melt pool. In all welding conditions, frequent small expansion at the keyhole bottom was observed. Therefore, the porosity formation mechanism is assumed to have a strong relationship with expansion of keyhole bottom, where major porosity was formed.
关键词： X-ray phase-contrast method,porosity formation,Aluminum alloy,laser welding,weld pool dynamics,keyhole dynamics
更新于2025-09-19 17:13:59
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An Influence of the Module Structure on Reliability of Crystalline Silicon Solar Cells
摘要： To investigate the influence of the difference in module structures on the degradation of crystalline silicon solar cells, two different photovoltaic modules were fabricated, and a high-temperature and high-humidity test was carried out. The degradation modes of these modules were compared to each other using electrical characteristics and electroluminescence images. Degradation of outputs occurred in both modules, and different degradation modes were confirmed by electroluminescence images. The difference in degradation modes between these modular structures could be due to the difference in concentration distribution attributable to the moisture and acetic acid generated from the encapsulant inside the module.
关键词： Moisture Ingress,Metallization,Damp Heat Test,Corrosion,Aluminum,Photovoltaic Module,Silver Paste
更新于2025-09-19 17:13:59
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Technological Feasibility of Lattice Materials by Laser-Based Powder Bed Fusion of A357.0
摘要： Lattice materials represent one of the utmost applications of additive manufacturing. The promising synergy between additive processes and topology optimization finds full development in achieving components that comprise bulky and hollow areas, as well as intermediate zones. Yet, the potential to design innovative shapes can be hindered by technological limits. The article tackles the manufacturability by laser-based powder bed fusion (L-PBF) of aluminum-based lattice materials by varying the beam diameter and thus the relative density. The printing accuracy is evaluated against the distinctive building phenomena in L-PBF of metals. The main finding consists in identification of a feasibility window that can be used for development of lightweight industrial components. A relative density of 20% compared with fully solid material (aluminum alloy A357.0) is found as the lowest boundary for a 3-mm cell dimension for a body-centered cubic structure with struts along the cube edges (BCCXYZ) and built with the vertical edges parallel to the growth direction to account for the worst-case scenario. Lighter structures of this kind, even if theoretically compliant with technical specifications of the machine, result in unstable frameworks.
关键词： additive manufacturing,lattice,aluminum alloy,laser-based powder bed fusion
更新于2025-09-19 17:13:59
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Chiral Second-Harmonic Generation from Monolayer WS <sub/>2</sub> /Aluminum Plasmonic Vortex Metalens
摘要： Two-dimensional spiral plasmonic structures have emerged as a versatile approach to generate near-field vortex fields with tunable topological charges. We demonstrate here a far-field approach to observe the chiral second-harmonic generation (SHG) at designated visible wavelengths from a single plasmonic vortex metalens. This metalens comprises an Archimedean spiral slit fabricated on atomically flat aluminum epitaxial film, which allows for precise tuning of plasmonic resonances and subsequent transfer of two-dimensional materials on top of the spiral slit. The nonlinear optical measurements show a giant SHG circular dichroism. Furthermore, we have achieved an enhanced chiral SHG conversion efficiency (about an order of magnitude greater than the bare aluminum lens) from monolayer tungsten disulfide (WS2)/aluminum metalens, which is designed at the C-exciton resonance of WS2. Since the C-exciton is not a valley exciton, the enhanced chiral SHG in this hybrid system originates from the plasmonic vortex field-enhanced SHG under the optical spin-orbit interaction.
关键词： optical spin-orbit interaction,Surface plasmonic vortex metalens,aluminum epitaxial film,chiral nonlinearity,second-harmonic generation,monolayer tungsten disulfide
更新于2025-09-19 17:13:59
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Modeling of Keyhole-Induced Pore Formation in Laser-Arc Hybrid Welding of Aluminum Alloy with a Horizontal Fillet Joint
摘要： A three-dimensional transient model is proposed to investigate the weld pool dynamic behavior in laser + metal inert gas (MIG) hybrid fillet welding of aluminum alloy in the horizontal position, which allows for the joint configuration and coupling of the keyhole, droplet and weld pool as well as the heat and mass exchange between gas and liquid phases and is able to simulate the temperature distribution, fluid flow and formation process of a keyhole-induced pore in hybrid welding with a horizontal fillet joint. The weld porosity is also measured using x-ray nondestructive testing technology. Keyhole behavior and the formation mechanism of keyhole-induced porosity were analyzed. The calculated results are in generally good agreement with the experimental ones. A clockwise vortex always exists at the middle part of the weld pool. The formation and growth of the molten metal bulge on the keyhole wall are responsible for the occurrence of a gas bubble, which has a variation in size and shape and can be split during welding. The keyhole collapses easily at its middle or upper part in horizontal fillet welding, and the capture of the bubble by the upper molten pool boundary enhances the possibility of porosity formation to some degree. The keyhole-induced pore is mainly formed at the regions near the keyhole bottom and the upper fusion line of the weld pool.
关键词： horizontal fillet joint,numerical analysis,aluminum alloy,hybrid welding,pore formation
更新于2025-09-19 17:13:59