Comparison of emission signals for femtosecond and nanosecond laser-ablated Cu plasmas by changing the distance from focusing-lens to target-surface at different target temperatures

2021 ◽  
pp. 106302
Author(s):  
Qiuyun Wang ◽  
Anmin Chen ◽  
Yitong Liu ◽  
Suyu Li ◽  
Mingxing Jin
Keyword(s):  
Target Surface ◽  
Nanosecond Laser ◽  
Focusing Lens

scholarly journals Discrimination of ablation, shielding, and interface layer effects on the steady-state formation of persistent bubbles under liquid flow conditions during laser synthesis of colloids

2021 ◽  
Author(s):  
Mark-Robert Kalus ◽  
Riskyanti Lanyumba ◽  
Stephan Barcikowski ◽  
Bilal Gökce
Keyword(s):  
Steady State ◽  
Laser Ablation ◽  
Liquid Flow ◽  
Production Efficiency ◽  
Synthesis Method ◽  
Target Surface ◽  
Interface Layer ◽  
Nanosecond Laser ◽  
Viscous Liquids ◽  
Shielding Effects

AbstractOver the past decade, laser ablation in liquids (LAL) was established as an innovative nanoparticle synthesis method obeying the principles of green chemistry. While one of the main advantages of this method is the absence of stabilizers leading to nanoparticles with “clean” ligand-free surfaces, its main disadvantage is the comparably low nanoparticle production efficiency dampening the sustainability of the method and preventing the use of laser-synthesized nanoparticles in applications that require high amounts of material. In this study, the effects of productivity-dampening entities that become particularly relevant for LAL with high repetition rate lasers, i.e., persistent bubbles or colloidal nanoparticles (NPs), on the synthesis of colloidal gold nanoparticles in different solvents are studied. Especially under batch ablation conditions in highly viscous liquids with prolonged ablation times both shielding entities are closely interconnected and need to be disentangled. By performing liquid flow-assisted nanosecond laser ablation of gold in liquids with different viscosity and nanoparticle or bubble diffusivity, it is shown that a steady-state is reached after a few seconds with fixed individual contributions of bubble- and colloid-induced shielding effects. By analyzing dimensionless numbers (i.e., Axial Peclet, Reynolds, and Schmidt) it is demonstrated how these shielding effects strongly depend on the liquid’s transport properties and the flow-induced formation of an interface layer along the target surface. In highly viscous liquids, the transport of NPs and persistent bubbles within this interface layer is strongly diffusion-controlled. This diffusion-limitation not only affects the agglomeration of the NPs but also leads to high local densities of NPs and bubbles near the target surface, shielding up to 80% of the laser power. Hence, the ablation rate does not only depend on the total amount of shielding matter in the flow channel, but also on the location of the persistent bubbles and NPs. By comparing LAL in different liquids, it is demonstrated that 30 times more gas is produced per ablated amount of substance in acetone and ethylene glycol compared to ablation in water. This finding confirms that chemical effects contribute to the liquid’s decomposition and the ablation yield as well. Furthermore, it is shown that the highest ablation efficiencies and monodisperse qualities are achieved in liquids with the lowest viscosities and gas formation rates at the highest volumetric flow rates.

Reflection Losses from Laser-Produced Plasmas

1977 ◽  
Vol 32 (10) ◽  
pp. 1100-1107 ◽  
Author(s):  
R. P. Godwin ◽  
C. G. M. van Kessel ◽  
J. N. Olsen ◽  
P. Sachsenmaier ◽  
R. Sigel ◽  
...  
Keyword(s):  
Pulse Energy ◽  
Solid Angle ◽  
Scattered Light ◽  
Target Material ◽  
Target Surface ◽  
Theoretical Models ◽  
Light Collection ◽  
Ellipsoidal Mirror ◽  
Sharp Focusing ◽  
Focusing Lens

Optical calorimetry of laser radiation reflected from plane targets irradiated by a 0.3 J/30 ps Nd-laser pulse (λ = 1.06 μm) has been performed. A 2π-ellipsoidal mirror was used for scattered light collection. We find that scattering outside the solid angle of the focusing lens is a major reflection loss from the target. A maximum fraction of 0.5 of the incident pulse energy was absorbed in the target with only a very weak dependence on pulse energy and target material. We emphasize that measurements made with sharp focusing on the target surface are difficult to compare with theoretical models in the plane wave/plane target approximation

scholarly journals PALS laser energy transfer into solid targets and its dependence on the lens focal point position with respect to the target surface

2008 ◽  
Vol 26 (2) ◽  
pp. 189-196 ◽  
Author(s):  
A. Kasperczuk ◽  
T. Pisarczyk ◽  
M. Kalal ◽  
M. Martinkova ◽  
J. Ullschmied ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Laser Energy ◽  
Focal Point ◽  
Target Surface ◽  
Plasma Jets ◽  
Point Position ◽  
Laser Plasma Interactions ◽  
Opposite Case ◽  
Laser Facility ◽  
Focusing Lens

AbstractThis paper is devoted to investigations of laser energy transfer into solid targets with respect to the focusing lens focal point position relative to the solid target surface as obtained at the PALS laser facility. The third harmonic of the PALS laser beam with energy ~90 J and pulse duration ~250 ps (FWHM) was used for irradiation of two kinds of targets made of Cu: a slab and a 3.6 µm thick foil. The focal point of the beam was located either inside or in front of the target surface, and care was taken to ensure the same laser spot radii in both cases (250 µm). It was demonstrated that these two opposite focal point positions give rise to significantly different laser-plasma interactions: with either depression or maximum of the laser intensity distribution in the center of the beam, respectively. It was also verified that the focal point position inside of the target is favorable for plasma jets creation, whereas the opposite case is more effective for acceleration of flyers.

scholarly journals Simultaneous measurement of self-generated magnetic fields and electron heat transport in dense plasma

2013 ◽  
Vol 31 (4) ◽  
pp. 653-661 ◽  
Author(s):  
L. Lancia ◽  
C. Fourment ◽  
J. Fuchs ◽  
J.-L. Feugeas ◽  
Ph. Nicolai ◽  
...  
Keyword(s):  
Heat Flux ◽  
Magnetic Fields ◽  
Heat Wave ◽  
Dense Plasma ◽  
Target Surface ◽  
Nanosecond Laser ◽  
Power Laser ◽  
Wave Propagation Velocity ◽  
Electron Heat

AbstractThe role of self generated magnetic fields in the transport of a heat wave following a nanosecond laser irradiation of a solid target is investigated. Magnetic fields are expected to localize the electron carrying the heat flux but at the same time are affected in their evolution by the heat flux itself. We performed simultaneous measurements of heat wave propagation velocity within the target and magnetic fields developing on the target surface. These were compared to results obtained by numerical magneto-hydrodynamic modeling, including self-generated B fields. The comparison shows that longitudinal heat flow is overestimated in the simulations. Similarly, but most notably, the radial expansion of the magnetic fields is underestimated by the modeling. The two are likely linked, the more pronounced radial drift of B-fields induces a rotation of heat flux in the radial direction, and corresponding longitudinal heat flux inhibition. This suggests the need for improving present modeling of self-generated magnetic fields evolution in high power laser-matter interaction.

scholarly journals Observation of repetitive bursts in emission of fast ions and neutrons in sub-nanosecond laser-solid experiments

2013 ◽  
Vol 31 (3) ◽  
pp. 395-401 ◽  
Author(s):  
J. Krása ◽  
D. Klír ◽  
A. Velyhan ◽  
D. Margarone ◽  
E. Krouský ◽  
...  
Keyword(s):  
Laser System ◽  
Target Surface ◽  
Current Mode ◽  
Energy Spectra ◽  
Nanosecond Laser ◽  
Fast Ions ◽  
Peak Energy ◽  
Fusion Neutrons ◽  
Deuterated Polyethylene ◽  
Broad Energy

AbstractA massive deuterated polyethylene target was exposed to laser intensities of about 3 × 1016 W/cm2 employing the 3-TW Prague Asterix Laser System (PALS). We achieved a yield of 2 × 108 neutrons per laser shot. Average time-of-flight signals of scintillation detectors operated in current mode reveal broad energy spectra of fusion neutrons with dominating energy of about 2.45 MeV. The energy dependence of the neutron yield shows a consistency in results of nanosecond, picosecond and sub-picosecond experiments. Here we also show that ions emitted in the backward direction from the front target surface have a multi-peak energy spectrum, which is caused by burst emission mechanisms.

Laser-Target Interactions and its Effect on Surface Morphology of Laser Deposited thin films

1990 ◽  
Vol 201 ◽  
Author(s):  
R. K. Singh ◽  
D. Bhattacharya ◽  
J. Narayan
Keyword(s):  
Energy Density ◽  
Particle Density ◽  
Target Material ◽  
Target Surface ◽  
Solid Material ◽  
Laser Evaporation ◽  
Nanosecond Laser ◽  
Laser Target ◽  
Surface Evaporation ◽  
Surface Temperatures

AbstractThe laser-target interactions during pulsed laser evaporation (PLE) of materials have been investigated in detail. Sub-surface temperatures have been calculated to be higher than the surface temperatures during planar surface evaporation of the target material. While the evaporating surface is being cooled due to the latent heat of vaporization, sub-surface superheating occurs due to the finite absorption depth of the laser beam. Detailed computer simulations have been carried out to understand the evaporation characteristics of different targets (Si, YBa2Cu3O7 ) as a function of laser and target variables. For silicon targets irradiated with 25 nanosecond laser pulses (energy density of 10J/cm2, absorption coefficient of 105 cm−1), the sub-surface temperatures were found to be more than 2000°C above the surface evaporation temperatures. The sub-surface superheating increased with increasing energy density and absorption depth. This internal superheating effects may lead to volume evaporation of the target where a solid material in form of particles may be ejected from the target surface. Based on the above understanding, parameters required to reduce the particle density in PLE films are predicted.

Impact of the lasr wavelength and fluence on the ablation rate of aluminium

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Mihai Stafe ◽  
Ionut Vladoiu ◽  
Ion Popescu
Keyword(s):  
Plasma Plume ◽  
Second Harmonic ◽  
Laser System ◽  
Target Surface ◽  
Threshold Value ◽  
Laser Pulses ◽  
Ablation Rate ◽  
Nanosecond Laser ◽  
Nanosecond Laser Pulses ◽  
532 Nm

AbstractThe dependence of the ablation rate of aluminium on the fluence of nanosecond laser pulses with wavelengths of 532 nm and respectively 1064 nm is investigated in atmospheric air. The fluence of the pulses is varied by changing the diameter of the irradiated area at the target surface, and the wavelength is varied by using the fundamental and the second harmonic of a Q-switched Nd-YAG laser system. The results indicate an approximately logarithmic increase of the ablation rate with the fluence for ablation rates smaller than ∼6 μm/pulse at 532 nm, and 0.3 μm/pulse at 1064 nm wavelength. The significantly smaller ablation rate at 1064 nm is due to the small optical absorptivity, the strong oxidation of the aluminium target, and to the strong attenuation of the pulses into the plasma plume at this wavelength. A jump of the ablation rate is observed at the fluence threshold value, which is ∼50 J/cm2 for the second harmonic, and ∼15 J/cm2 for the fundamental pulses. Further increasing the fluence leads to a steep increase of the ablation rate at both wavelengths, the increase of the ablation rate being approximately exponential in the case of visible pulses. The jump of the ablation rate at the threshold fluence value is due to the transition from a normal vaporization regime to a phase explosion regime, and to the change of the dimensionality of the hydrodynamics of the plasma-plume.

scholarly journals Effect of Crystallographic Orientation on Structural Response of Silicon to Femtosecond Laser Irradiation

2021 ◽  
Author(s):  
Xin Zhang ◽  
Liang Zhang ◽  
Sergey Mironov ◽  
Rongshi Xiao ◽  
Liang Guo ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Crystallographic Orientation ◽  
Electron Backscatter Diffraction ◽  
Structural Response ◽  
Target Material ◽  
Target Surface ◽  
Femtosecond Laser Irradiation ◽  
Nanosecond Laser ◽  
Transmission Electron ◽  
Thermal Melting

Abstract Femtosecond laser has been widely utilized for modification of crystal structure to achieve desired functions. So far, however, the effect of crystallographic orientation on the induced structure by femtosecond laser processing has yet been comprehensively studied. The present work is undertaken in an attempt to fill this gap in our knowledge. To this end, commercial-purity Si is used as a target material and high-resolution transmission electron microscopy as well as electron backscatter diffraction are applied to examine the irradiation-induced microstructural changes. The structural response of the pulsed material is found to be principally influenced by the crystallographic orientation of the target surface. Specifically, at the surface orientation close to {111}, a pronounced amorphization effect is observed whereas no disordered material is detected at the orientations close to {100}. This phenomenon could be explained by the lowest crystallization speed required by the (111) surface due to its smallest surface energy. Compared with nanosecond laser, non-thermal melting induced by femtosecond laser induces mild thermal gradient and favors recrystallization.

Sign in / Sign up

Export Citation Format

Share Document