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The Influence of Laser Ablation Parameters on the Holes Structure of Laser Manufactured Graphene Paper Microsieves
摘要： The graphene paper microsieves can be applied in the ?ltration of biological ?uids or separation of solid particles from exploitation ?uids. To produce graphene paper microsieves for speci?c applications, good control over fabrication should be achieved. In this study, a laser ablation method using a picosecond laser was applied to fabricate graphene paper microsieves. Holes in the microsieves were drilled using pulsed laser radiation with a pulse energy from 5 to 100 μJ, a duration of 60 ps, a wavelength of 355 nm, and a repetition rate of 1 kHz. The impact method was applied using 10 to 100 pulses to drill one hole. To produce holes of a proper diameter which could separate biological particles of a certain size (≥10 μm), optimum parameters of graphene paper laser ablation were de?ned using the MATLAB software taking into account laser pulse energy, repetition rate, and a desired hole diameter. A series of structural tests were carried out to determine the quality of an edge and a hole shape. Experimental results and Laguerre–Gauss calculations in MATLAB were then compared to perform the analysis of the distribution of di?raction fringes. Optimum experimental parameters were determined for which good susceptibility of the graphene paper to laser processing was observed.
关键词： laser manufacturing,graphene paper,picosecond laser,graphene paper microsieves,laser ablation
更新于2025-09-23 15:19:57
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Development of Picosecond Laser Writing for Heat Resistant FBG Sensors and Adhesion Technique for High Temperature Industrial Plants; ?????3?§??????????????·￥?????????è????±FBG ?????3??μè￡??????¨é???????￡?￥-??¨????????3???????????￥???;
摘要： Pulse laser processing point by point method is applied for heat resistant Fiber Bragg Grating structure. In order to fabricate fine FBG, a close packaged picosecond laser system is used with a CCD camera microscopy. An optical fiber is mounted on a precision translation stage. The stage speed is controlled by the current position and the corrector output. In order to contact the FBG on a metal surface, nano-size colloidal silver adhesive is used under temperature monitoring. Heat expansion of SUS plate can be successfully monitored by strain gauge of the heat resistant FBG. It can be available for monitoring the structural integrity of high temperature industrial plant. Complex coolant piping systems of liquid sodium and molten salt are facing the risk of coolant leakage, which is the most promising usage.
关键词： Structural Health Integrity,Picosecond Laser Processing,Adhesion,High Temperature,FBG
更新于2025-09-23 15:19:57
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Development of Method Enhanced Laser Ablation Efficiency According to Fine Curvature of the Polymer through the Preliminary Preparation Process Using UV Picosecond Laser
摘要： In processes using the ultrashort pulsed laser, the phenomenon that the ablation efficiency is reduced due to the increase of the shielding effect of the generated plume is increasingly caused by the use of the high power and high repetition rate. A new method is needed to prevent a decrease in ablation efficiency in processing using an ultrashort pulsed laser. In this study, the proposed a processing method that can improve the ablation efficiency by providing an efficient escape path of plume, and examine the feasibility of a new processing method. The new method we proposed is a method of laser processing after generating a fine curvature in the polymer as a preliminary preparation. The fine curvature of the polymer produced by the preliminary preparation induces an artificial chimney-like opening along the path of the incident beam during laser processing, thereby enabling the plume to be effectively removed. The experiment for examine the feasibility through a new method was conducted using a 10-picosecond laser of UV wavelength with two optical systems. As a new processing method, when processing with ultrashort pulse laser, it was observed that the ablation efficiency improved.
关键词： fine curvature of polymer,picosecond pulse laser,artificial chimney,laser ablation,enhanced laser ablation efficiency
更新于2025-09-23 15:19:57
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Nanoplasma-enabled picosecond switches for ultrafast electronics
摘要： The broad applications of ultrawide-band signals and terahertz waves in quantum measurements, imaging and sensing techniques, advanced biological treatments, and very-high-data-rate communications have drawn extensive attention to ultrafast electronics. In such applications, high-speed operation of electronic switches is challenging, especially when high-amplitude output signals are required. For instance, although field-effect and bipolar junction devices have good controllability and robust performance, their relatively large output capacitance with respect to their ON-state current substantially limits their switching speed. Here we demonstrate a novel on-chip, all-electronic device based on a nanoscale plasma (nanoplasma) that enables picosecond switching of electric signals with a wide range of power levels. The very high electric field in the small volume of the nanoplasma leads to ultrafast electron transfer, resulting in extremely short time responses. We achieved an ultrafast switching speed, higher than 10 volts per picosecond, which is about two orders of magnitude larger than that of field-effect transistors and more than ten times faster than that of conventional electronic switches. We measured extremely short rise times down to five picoseconds, which were limited by the employed measurement set-up. By integrating these devices with dipole antennas, high-power terahertz signals with a power–frequency trade-off of 600 milliwatts terahertz squared were emitted, much greater than that achieved by the state of the art in compact solid-state electronics. The ease of integration and the compactness of the nanoplasma switches could enable their implementation in several fields, such as imaging, sensing, communications and biomedical applications.
关键词： picosecond switches,terahertz waves,ultrafast electronics,nanoplasma,electronic switches
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Autonomous Path Planning by Unmanned Aerial Vehicle (UAV) for Precise Monitoring of Large-Scale PV plants
摘要： This paper presents a 3.6 GHz low-noise fractional-N digital phase-locked loop (PLL) that achieves low in-band phase noise. Phase detection is carried out by a proposed 10-bit, 0.8 ps resolution time-to-digital converter (TDC) using a charge pump and a successive-approximation-register analog-to-digital converter (SAR-ADC) with low power and small area. The latency of the TDC is addressed by the designed building blocks. The fractional spurs are reduced by dual-loop least-mean-square (LMS) calibration. A (cid:2)(cid:3)-less and MOS varactor-less LC digitally-controlled oscillator (DCO) is proposed whose frequency resolution is enhanced to 7 kHz (or a unit variable capacitance of 2.6 aF) using a bridging capacitor technique. A prototype chip is fabricated using a 65 nm CMOS process, occupying an active area of 0.38 mm2 and consuming a power of 9.7 mW at a reference frequency of 50 MHz. The measured in-band phase noise is 107.8 dBc/Hz to 110.0 dBc/Hz with a loop bandwidth of 1 to 5 MHz.
关键词： digitally controlled oscillator (DCO),least-mean-square (LMS),digital phase-locked-loop (PLL),time-to-digital converter (TDC),successive-approximation-register analog-to-digital converter (SAR-ADC),frequency synthesizer,CMOS,sub-picosecond resolution
更新于2025-09-23 15:19:57
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Spectral dynamics of shift current in ferroelectric semiconductor SbSI
摘要： Photoexcitation in solids brings about transitions of electrons/holes between different electronic bands. If the solid lacks an inversion symmetry, these electronic transitions support spontaneous photocurrent due to the geometric phase of the constituting electronic bands: the Berry connection. This photocurrent, termed shift current, is expected to emerge on the timescale of primary photoexcitation process. We observe ultrafast evolution of the shift current in a prototypical ferroelectric semiconductor antimony sulfur iodide (SbSI) by detecting emitted terahertz electromagnetic waves. By sweeping the excitation photon energy across the bandgap, ultrafast electron dynamics as a source of terahertz emission abruptly changes its nature, reflecting a contribution of Berry connection on interband optical transition. The shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a subpicosecond timescale. Understanding these substantive characters of the shift current with the help of first-principles calculation will pave the way for its application to ultrafast sensors and solar cells.
关键词： photovoltaic effect,ferroelectricity,picosecond techniques,solar cells,bulk matter
更新于2025-09-19 17:15:36
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Fabrication of silicon carbide nanoparticles using picosecond pulsed laser ablation in acetone with characterizations from TEM and XRD
摘要： We fabricated SiC nanoparticles (NPs) using a laser ablation method in acetone with a picosecond pulsed laser and characterized the resulting sizes, shapes, and crystal structures using transmission electron microscopy (TEM) and X-ray diffraction (XRD). We revealed two formation processes for the SiC NPs. The main process was the formation of spherical NPs with diameters primarily less than 10 nm. The crystal structure was 3C-SiC, which did not depend on a target polytype. Therefore, it is concluded that these NPs are grown from atomic molecules that disassociate from targets in the ablation process. As a result of a Rietbelt analysis of the XRD patterns, we clearly found that almost all NPs were single crystals. In addition, a stacking fault in the crystal was observed in the TEM image, which affects the XRD pattern. The other process was the formation of NPs with diameters from 30 to 80 nm with crystal structures that were the same as the targets. This indicates that these NPs were generated as fragments of the target. Our findings are useful for applications of SiC NPs to selectively control their size, shape, and crystal structure using laser ablation.
关键词： silicon carbide nanoparticles,3C-SiC,picosecond pulsed laser ablation,TEM,XRD
更新于2025-09-19 17:13:59
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Express: Time-Gated Single-Shot Picosecond Laser-Induced Breakdown Spectroscopy (ps-LIBS) for Equivalence-Ratio Measurements
摘要： Time-gated picosecond laser-induced breakdown spectroscopy (ps-LIBS) for the determination of local equivalence ratios in atmospheric-pressure adiabatic methane–air flames is demonstrated. Traditional LIBS for equivalence-ratio measurements employ nanosecond (ns)-laser pulses, which generate excessive amounts of continuum, reducing measurement accuracy and precision. Shorter pulse durations reduce the continuum emission by limiting avalanche ionization. Furthermore, by contrast the use of femtosecond lasers, plasma emission via picosecond-laser excitation has high signal-to-noise ratio (S/N), allowing single-shot measurements suitable for equivalence-ratio determination in turbulent reacting flows. We carried out an analysis of the dependence of the plasma emission ratio Hα (656 nm)/NII (568 nm) on laser energy and time-delay for optimization of S/N and minimization of measurement uncertainties in the equivalence ratios. Our finding shows that higher laser energy and shorter time delay reduces measurement uncertainty while maintaining high S/N. In addition to atmospheric-pressure flame studies, we also examine the stability of the ps-LIBS signal in a high-pressure nitrogen cell. The results indicate that the plasma emission and spatial position could be stable, shot-to-shot, at elevated pressure (up to 40 bar) using a lower excitation energy. Our work shows the potential of using ps-duration pulses to improve LIBS-based equivalence-ratio measurements, both in atmospheric and high-pressure combustion environments.
关键词： time-resolved spectroscopy,combustion diagnostics,Laser-induced breakdown spectroscopy,picosecond phenomena,LIBS
更新于2025-09-19 17:13:59
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Treatment of acne scars with a fractional 1064a??nm Nd:YAG picosecond laser and histopathologic findings
摘要： Atrophic acne scars have been treated using a non-ablative fractional 1550 nm laser for more than 15 years. Recently, Non-ablative fractional delivery of a 1064 nm picosecond laser was used to treat scars. This laser’s ultrashort pulses trigger photomechanical effects based on selective photothermolysis (Habbema, Verhagen, Van Hal, Liu & Varghese, 2012). We report successful treatment of acne scars and point toward its treatment mechanism by showing histopathologic findings.
关键词： Scar,Picosecond,Acne
更新于2025-09-19 17:13:59
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Influence of double pulse ablation on the film topography in picosecond pulsed laser deposition of nickel
摘要： An approach to achieve co-axial picosecond laser pulsed pair is proposed. Instead of introducing additional optical devices, this method involves the adjustment of switching-out dynamics in the regenerative amplification process. Experimental results concerning the dependence of laser output behavior on the duration of the quarter-wave voltage applied on the Pockels cell are reported. The influence of ablation mode (single pulse or double pulse) on the morphology of deposited Nickel-films is studied. A significant improvement in the surface morphology with the double pulse mode is observed. Fewer nanoparticles are observed and the thin film appears to be smoother with lower roughness.
关键词： double pulse ablation,nickel,film topography,picosecond pulsed laser deposition
更新于2025-09-19 17:13:59