scholarly journals Regular Nanowire Formation on Fe-Based Metal Glass by Manipulation of Surface Waves

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2389
Author(s):  
Zhen Zhao ◽  
Chaoqun Xia ◽  
Jianjun Yang
Keyword(s):  
Laser Fluence ◽  
Delay Time ◽  
Femtosecond Lasers ◽  
Regular Structure ◽  
Laser Pulses ◽  
Structural Features ◽  
Magnetic Surface ◽  
Laser Wavelength ◽  
Inhomogeneous Magnetization ◽  
Nanowire Structure

We report the formation of a sole long nanowire structure and the regular nanowire arrays inside a groove on the surface of Fe-based metallic glass upon irradiation of two temporally delayed femtosecond lasers with the identical linear polarization parallel and perpendicular to the groove, respectively. The regular structure formation can be well observed within the delay time of 20 ps for a given total laser fluence of F = 30 mJ/cm2 and within a total laser fluence range of F = 30–42 mJ/cm2 for a given delay time of 5 ps. The structural features, including the unit width and distribution period, are measured on a one-hundred nanometer scale, much less than the incident laser wavelength of 800 nm. The degree of structure regularity sharply contrasts with traditional observations. To comprehensively understand such phenomena, we propose a new physical model by considering the spin angular momentum of surface plasmon and its enhanced inhomogeneous magnetization for the ferromagnetic metal. Therefore, an intensive TE polarized magnetic surface wave is excited to result in the nanometer-scaled energy fringes and the ablative troughs. The theory is further verified by the observation of nanowire structure disappearance at the larger time delays of two laser pulses.

electromagnetic field at the particl e has to be computed numerically. An example of such a computation using a program based on [49] is given in Fig. 4. But not only doe s the Mie theory describe an enhancement of the laser intensity in the particles' near field, it also predicts that for certain values of the size parameter nd/X (d denoting the particle diameter, À the laser wavelength) the enhancement should be particularly efficient, resulting in a resonant intensity enhancement, the so-called "Mie-resonances". 3.2.2. Near-field induced substrate damage When inspecting contaminated samples by scanning electron microscopy (SEM) or atomic force microscopy (AFM ) after DLC using ns laser pulses, the consequences of the field enhancement process became obvious: all over the cleaned areas w e found substrate damages localized exactly at the former particle positions [35, 37-39]. These damages manifested as melting pools or even holes in the surface, typical examples can be seen in Fig. 5. The consequences for the laser cleaning process are obvious. The intensity enhancement reduces the maximum laser fluence that can be applied in the process. Usually in laser cleaning studies [19, 31 ] the laser fluence corresponding to the melting threshold of a bare surface is taken as the damage threshold fluence. Our experiments show clearly that this is an inadequate definition. Instead one must take into account the enhanced laser fluence underneath the particles, as it will be discussed in Section 4. Fro m the obtained AFM images we were able to analyse in detail the surface profile at the damaged sites. Here we found that for high field enhancement factors the silicon substrate was not only molten , but that some material was even ablated (see Sec. 4). The momentum transfer to the particles during the ablation process significantly contributes to the cleanin g process and hence local substrate ablation

2003 ◽  
pp. 327-330
Keyword(s):  
Laser Fluence ◽  
Near Field ◽  
Particle Diameter ◽  
Surface Profile ◽  
Field Enhancement ◽  
Damage Threshold ◽  
Laser Pulses ◽  
Laser Wavelength ◽  
Laser Cleaning ◽  
Intensity Enhancement

scholarly journals Laser assisted bioprinting at different wavelengths and pulse durations with a metal dynamic release layer: A parametric study

2017 ◽  
Vol 3 (1) ◽  
Author(s):  
Lothar Koch ◽  
Ole Brandt ◽  
Andrea Deiwick ◽  
Boris Chichkov
Keyword(s):  
Laser Pulse ◽  
Focal Spot ◽  
Femtosecond Lasers ◽  
Metal Layer ◽  
Laser Pulses ◽  
Spot Size ◽  
Laser Wavelength ◽  
Focal Spot Size ◽  
Gold Silver ◽  
Absorbing Material

 For more than a decade living cells and biomaterials (typically hydrogels) have been printed with laser-assisted bioprinting. Often, a thin metal layer is applied as laser-absorbing material, called dynamic release layer (DRL). This layer is vaporized by focused laser pulses generating vapor pressure that propels forward a coated biomaterial. Different lasers with laser wavelengths from 193 to 1064 nanometer have been used. As a metal DRL gold, silver, or titanium layers have been used. The applied laser pulse durations were usually in the nanosecond range from 1 to 30 ns. In addition, some studies with femtosecond lasers have been published. However, there are no studies on the effect of all these lasers parameters on bioprinting with a metal DRL, comparing different wavelengths and pulse durations – except one study comparing 500 femtosecond pulses with 15 ns pulses. In this paper, the effects of laser wavelength (355, 532, and 1064 nm) and laser pulse duration (in the range of 8 to 200 ns) are investigated. Furthermore, the effects of laser pulse energy, intensity, and focal spot size are studied. The printed droplet volume, hydrogel jet velocity, and cell viability are analyzed.

scholarly journals High-quality percussion drilling with ultrashort laser pulses

2021 ◽  
Vol 127 (9) ◽  
Author(s):  
A. Feuer ◽  
R. Weber ◽  
R. Feuer ◽  
D. Brinkmeier ◽  
T. Graf
Keyword(s):  
Stainless Steel ◽  
Laser Fluence ◽  
Ablation Threshold ◽  
Laser Pulses ◽  
Ultrashort Laser Pulses ◽  
High Quality ◽  
Edge Quality ◽  
Ultrashort Laser ◽  
Percussion Drilling

AbstractThe influence of the laser fluence on the quality of percussion-drilled holes was investigated both experimentally and by an analytical model. The study reveals that the edge quality of the drilled microholes depends on the laser fluence reaching the rear exit of the hole and changes with the number of pulses applied after breakthrough. The minimum fluence that must reach the hole’s exit in order to obtain high-quality microholes in stainless steel was experimentally found to be 2.8 times the ablation threshold.

2D organic-inorganic hybrid perovskite materials for nonlinear optics

Nanophotonics ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1787-1810 ◽  
Author(s):  
Xiao Han ◽  
Yongshen Zheng ◽  
Siqian Chai ◽  
Songhua Chen ◽  
Jialiang Xu
Keyword(s):  
Nonlinear Optical ◽  
Second Harmonic ◽  
Low Cost ◽  
Laser Pulses ◽  
Structural Features ◽  
Photon Absorption ◽  
Saturable Absorption ◽  
Research Attention ◽  
Inorganic Hybrid ◽  
Quantum Well Structures

AbstractTwo-dimensional (2D) organic-inorganic hybrid perovskites feature characteristics of inherent quantum-well structures and intriguing optoelectronic properties, and have therefore attracted enormous research attention for their optical applications in light emitting, sensing, modulation, and telecommunication devices. The low-cost and solution-processed fabrications as well as alternative organic spacer cations endue 2D hybrid perovskites with higher tunability in optical and photonic applications. In particular, they demonstrate distinguished nonlinear optical characters such as second-harmonic generation (SHG), two-photon absorption (2PA), and saturable absorption (SA) under the excitation of laser pulses. Here, we discuss the construction of the various sorts of 2D hybrid perovskites with different structural features. We have also highlighted some representative properties and applications of these 2D hybrid perovskites in both linear and nonlinear optical regimes.

Pump-Probe Laser Photolytic Fragmentation Fluorescence Spectrometry of Isomeric Alkenes

1994 ◽  
Vol 48 (5) ◽  
pp. 616-619 ◽  
Author(s):  
Bobby J. Stanton ◽  
E. T. Monroe ◽  
E. L. Wehry
Keyword(s):  
Fluorescence Intensity ◽  
Laser Fluence ◽  
Laser Wavelength ◽  
Fluorescence Spectrometry ◽  
Probe Laser ◽  
Intermediate Species ◽  
Pump Probe ◽  
Laser Pump ◽  
Photolysis Laser ◽  
Spectral Patterns

The two-laser “pump-probe” photolytic fragmentation fluorescence spectrometry of three octenes and two nonenes is described. Probe-laser-induced C2 fluorescence (Deslandres-d'Azambuja system, C1II g→ A1II u) is detected. The relative C2 fluorescence intensity and spectral patterns exhibited by each alkene are strongly dependent on the probe-laser wavelength. The dependence of the fragment fluorescence intensity on the probe-laser fluence implies that the “probe” laser induces photofragmentation of intermediate species produced by the “photolysis” laser.

Core-Shell SiO2/Ag Composite Spheres Prepared by Electrical Exploding Wire Plasma Technique: Synthesis and Characterization

2021 ◽  
Vol 19 (10) ◽  
pp. 82-88
Author(s):  
Duaa A. Uamran ◽  
Qasim Hassan Ubaid ◽  
Hammad R. Humud
Keyword(s):  
Laser Pulse ◽  
Laser Pulses ◽  
Structural Features ◽  
Optical Absorption Spectroscopy ◽  
Core Shell ◽  
X Ray Diffraction ◽  
Shell Nanoparticles ◽  
X Ray ◽  
Photocatalytic Activities ◽  
Core Shell Nanoparticles

Core-shell nanoparticles (SiO2/Ag) were manufactured by using a two-step process: Electric detonation of Ag. Wire in colloidal solution particles then by using laser pulses, nanoparticles are released. The structural features of these nanoparticles were checked by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The (XRD) study showed the progressive coverage of SiO2/Ag by nanoparticles according to the energies of the laser pulse. Measurements of morphology and EDX confirmed the Core/shell structure with particle size at the nano level. It confirmed that preliminary analysis consists of a SiO2 core and an Ag shell from FESEM. The surface of the microscopic balls (SiO2) has been covered completely and homogeneously with Ag nanoparticles, Moreover, Ultraviolet-Visible, and by optical absorption spectroscopy, the Nanoparticles with core crust SiO2/Ag showed excellent photocatalytic activities at various concentrations and laser pulse energy.

A STUDY OF FEMTOSECOND LASER POLISHING OF CVD NANOPOLYCRYSTALLINE DIAMOND FILMS

2021 ◽  
pp. 2150023
Author(s):  
YU-XIAO CUI ◽  
PING GUO ◽  
XUEMING ZHU ◽  
YAN-LING TIAN ◽  
DA-WEI ZHANG ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Fluence ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Laser Pulses ◽  
Promising Technique ◽  
Laser Polishing ◽  
Laser Fluences ◽  
Fs Laser ◽  
The Mean

Femtosecond (fs) laser ablation has been recognized as an effective and promising technique for high-precision processing of natural and synthesized diamond. In this work, a study of femtosecond laser polishing for nanopolycrystalline diamond (NCD) films by chemical vapor deposition (CVD) is reported. The laser irradiation is induced by 200-fs laser pulses with a repetition frequency of 50[Formula: see text]MHz, and various laser fluences are employed to investigate their polishing effectiveness. The results show that the optimal laser fluence is 0.7[Formula: see text]J/cm2, at which the nanodiamond grains on top of the cauliflower-like clusters of NCD films can be ablated. With such laser fluence, the mean surface roughness of NCD films reduces from 73.84[Formula: see text]nm to 31.88[Formula: see text]nm, which presents a 57% reduction. Nevertheless, when the laser fluence rises beyond 0.7[Formula: see text]J/cm2, large amount of amorphous carbon (a-C) balls and porous lava-like morphology would come into being, resulting in severe degradation of the NCD surface.

scholarly journals Correlations in Scattered X-Ray Laser Pulses Reveal Nanoscale Structural Features of Viruses

2017 ◽  
Vol 119 (15) ◽  
Author(s):  
Ruslan P. Kurta ◽  
Jeffrey J. Donatelli ◽  
Chun Hong Yoon ◽  
Peter Berntsen ◽  
Johan Bielecki ◽  
...  
Keyword(s):  
Laser Pulses ◽  
Structural Features ◽  
X Ray

scholarly journals Scanning electron microscope studies on laser ablation of solids

2019 ◽  
Vol 37 (01) ◽  
pp. 101-109 ◽  
Author(s):  
Mohamed E. Shaheen ◽  
Joel E. Gagnon ◽  
Brian J. Fryer
Keyword(s):  
Pulse Width ◽  
Laser Energy ◽  
Laser System ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Ablation Rate ◽  
Laser Wavelength ◽  
High Laser Fluence ◽  
Electron Imaging ◽  
Scanning Electron

AbstractThis study investigates the interaction of picosecond laser pulses with sapphire and brass in air using scanning electron microscopy. A picosecond laser system operating at a wavelength of 785 nm, pulse width of 110 ps, and variable repetition rate (1–1000 Hz) was used in this study. The pulse width applied in this work was not widely investigated as it lies in the gap between ultrashort (femtosecond) and long (nanosecond) pulse width lasers. Different surface morphologies were identified using secondary electron and backscattered electron imaging of the ablated material. Thermal ablation effects were more dominant in brass than in sapphire. Exfoliation and fractures of sapphire were observed at high laser fluence. Compared with brass, multiple laser pulses were necessary to initiate ablation in sapphire due to its poor absorption to the incident laser wavelength. Ablation rate of sapphire was lower than that of brass due to the dissipation of a portion of the laser energy due to heating and fracturing of the surface.

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