scholarly journals Simulation of optical breakdown in nitrogen by focused short laser pulses of 1064 nm wavelength

2008 ◽  
Vol 26 (4) ◽  
pp. 567-573 ◽  
Author(s):  
G. Tartar ◽  
H. Ranner ◽  
F. Winter ◽  
E. Wintner
Keyword(s):  
Laser Pulse ◽  
Pulse Energy ◽  
Dynamic Process ◽  
Collision Cross Section ◽  
Optical Breakdown ◽  
Initial Pressure ◽  
Spot Size ◽  
Laser Wavelength ◽  
Intense Laser ◽  
Electron Recombination

AbstractA kinetic model of electron cascade growth in the electromagnetic field of a focused intense laser pulse as used for laser spark generation in gases has been numerically implemented in Visual C code. The effects considered comprise Drude absorption, diffusive kinetic and inelastic losses as well as (three-particle) electron recombination. The objectives were to illustrate the dynamic process of gas ionization, and to clarify the pressure dependence of known breakdown thresholds within a range of about 2 × 104 to 2 × 106 Pa of initial pressure. Two-dimensional (cylindric coordinates) simulations of the optical breakdown in nitrogen were conducted on a commercial PC, using constant values for the collision cross section (2 × 10−19 m2), prevalent electronic excitation states (~4.8 eV), and a laser wavelength of 1064 nm. A certain aerosol concentration on the order of 3 ppb was assumed in order to provide initial electrons for cascade growth. Exemplary results with laser pulse energy of 26 mJ, pulse duration of 14 ns and an 18 µm focal spot size illustrate the dynamic process of ionization within a very short time period of less than 0.5 ns. The kinetic energy of the electrons is found to increase sharply up to more than 100,000 K on breakdown. A series of simulations considered the minimum pulse energy of breakdown (MPE) under variation of initial pressure. Identical laser parameters as in experiments conducted previously were used and the results are in excellent agreement with respect to curve shapes, i.e., MPE ~1/p0.4 in the first experiment and MPE ~1/p0.3 in the second one. The absolute values lie within a factor of two, which is explained by model abstraction and input data uncertainties.

Effect of obliquely external magnetic field on the intense laser pulse propagating in plasma medium

2020 ◽  
Vol 34 (07) ◽  
pp. 2050044
Author(s):  
Mehdi Abedi-Varaki
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Laser Pulse ◽  
Magnetoactive Plasma ◽  
Spot Size ◽  
The Self ◽  
Intense Laser ◽  
Intense Laser Pulse ◽  
Laser Spot Size ◽  
Self Focusing

In this paper, self-focusing of intense laser pulse propagating along the obliquely external magnetic field on the collisional magnetoactive plasma by using the perturbation theory have been studied. The wave equation describing the interaction of intense laser pulse with collisional magnetoactive plasma is derived. In addition, employing source-dependent expansion (SDE) method, the analysis of the laser spot-size is discussed. It is shown that with increasing of the angle in obliquely external magnetic field, the spot-size of laser pulse decreases and as a result laser pulse becomes more focused. Furthermore, it is concluded that the self-focusing quality of the laser pulse has been enhanced due to the presence of obliquely external magnetic field in the collisional magnetoactive plasma. Besides, it is seen that with increasing of [Formula: see text], the laser spot-size reduces and subsequently the self-focusing of the laser pulse in plasma enhances. Moreover, it is found that changing the collision effect in the magnetoactive plasma leads to increases of self-focusing properties.

scholarly journals Self focusing of a laser pulse in plasma with periodic density ripple

2009 ◽  
Vol 27 (2) ◽  
pp. 193-199 ◽  
Author(s):  
Sukhdeep Kaur ◽  
A.K. Sharma
Keyword(s):  
Laser Pulse ◽  
Spot Size ◽  
High Plasma ◽  
The Self ◽  
Intense Laser ◽  
Wave Number ◽  
Plasma Parameters ◽  
Density Region ◽  
Focusing Effect ◽  
Self Focusing

AbstractPropagation of an intense laser pulse in plasma with a periodically modulated density is considered using envelope equations. The laser induces modifications of the plasma refractive indexviarelativistic and ponderomotive nonlinearities. In the region of high plasma density, the self focusing effect of nonlinearity suppresses the diffraction divergence, and the laser converges. As the beam enters into the low density region, the diffraction tends to diverge it offsetting the convergence due to the curvature it has acquired. For a given set of plasma parameters, there is a critical power of the laser above which it propagates in a periodically focused manner. Below this power the laser undergoes overall divergence. At substantially higher powers, the laser beam continues to converge until the saturation effect of nonlinearity suppresses the self focusing and diffraction predominates. The effect of density ripple is to cause overall increase in the self focusing length. The minimum spot size decreases with the wave number of the ripple.

scholarly journals Magnetic Field Amplification Driven by the Gyro Motion of Charged Particles

2021 ◽  
Author(s):  
Yan-Jun Gu ◽  
Masakatsu Murakami
Keyword(s):  
Magnetic Field ◽  
Spot Size ◽  
Opposite Polarity ◽  
Laser Wavelength ◽  
Intense Laser ◽  
Magnetic Field Generation ◽  
Plasma Dynamics ◽  
Static Magnetic Fields ◽  
Laser Plasma Interactions ◽  
Field Amplification

Abstract Spontaneous magnetic field generation plays important role in laser-plasma interactions. Strong quasi-static magnetic fields affect the thermal conductivity and the plasma dynamics, particularly in the case of ultra intense laser where the magnetic part of Lorentz force becomes as significant as the electric part. Kinetic simulations of giga-gauss magnetic field amplification via a laser irradiated microtube structure reveal the dynamics of charged particle implosions and the mechanism of magnetic field growth. A giga-gauss magnetic field is generated and amplified with the opposite polarity to the seed magnetic field. The spot size of the field is comparable to the laser wavelength, and the lifetime is hundreds of femtoseconds. An analytical model is presented to explain the underlying physics. This study should aid in designing future experiments.

scholarly journals Effects of Laser Wavelength on Hot Electrons Produced by Ultrashort Intense Laser Pulse on Solid-Density Targets.

2002 ◽  
Vol 78 (8) ◽  
pp. 717-718 ◽  
Author(s):  
Susumu KATO ◽  
Eisuke MIURA ◽  
Eiichi TAKAHASHI ◽  
Tatsufumi NAKAMURA ◽  
Tomokazu KATO ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Laser Wavelength ◽  
Hot Electrons ◽  
Intense Laser ◽  
Intense Laser Pulse ◽  
Solid Density

scholarly journals Magnetic field amplification driven by the gyro motion of charged particles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yan-Jun Gu ◽  
Masakatsu Murakami
Keyword(s):  
Magnetic Field ◽  
Spot Size ◽  
Opposite Polarity ◽  
Laser Wavelength ◽  
Intense Laser ◽  
Magnetic Field Generation ◽  
Plasma Dynamics ◽  
Static Magnetic Fields ◽  
Laser Plasma Interactions ◽  
Field Amplification

AbstractSpontaneous magnetic field generation plays important role in laser-plasma interactions. Strong quasi-static magnetic fields affect the thermal conductivity and the plasma dynamics, particularly in the case of ultra intense laser where the magnetic part of Lorentz force becomes as significant as the electric part. Kinetic simulations of giga-gauss magnetic field amplification via a laser irradiated microtube structure reveal the dynamics of charged particle implosions and the mechanism of magnetic field growth. A giga-gauss magnetic field is generated and amplified with the opposite polarity to the seed magnetic field. The spot size of the field is comparable to the laser wavelength, and the lifetime is hundreds of femtoseconds. An analytical model is presented to explain the underlying physics. This study should aid in designing future experiments.

Femtosecond and Nanosecond Laser Pulse Crystallization of Thin a-Si:H Films on Non-Refractory Glass Substrates

2007 ◽  
Vol 131-133 ◽  
pp. 479-484 ◽  
Author(s):  
Vladimir A. Volodin ◽  
M.D. Efremov ◽  
G.A. Kachurin ◽  
S.A. Kochubei ◽  
A.G. Cherkov ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Energy Density ◽  
Laser Pulse ◽  
Raman Scattering ◽  
Pulse Energy ◽  
Laser Wavelength ◽  
Nanosecond Laser ◽  
Glass Substrates ◽  
Pulse Energy Density ◽  
Krf Laser

Thin (90 nm) a-Si:H films on Corning 7059 glass substrates have been crystallized by 120 fs pulses of Ti:sapphire and nanosecond pulse XeCl and KrF excimer lasers. Initial films were deposited using low-temperature plasma enhanced deposition technique. The structural properties of the films were characterized using the spectroscopy of Raman scattering, excited by the argon laser (line 514.5 nm) and using electron microscopy. For the femtosecond pulse treatments the ablation threshold was found to be some more than 65 mJ/cm2. When pulse energy density was lower than ~30 mJ/cm2 no structural changes were observed. In optimal regimes the films were found to be fully crystallized with needle grain structure, according to the Raman scattering and electron microscopy data. Estimates show the pulse energy density was lower than the Si melting threshold, so non-thermal “explosive” impacts may play some role. The main result in nanosecond XeCl and KrF laser pulse crystallization is the narrower window between beginning of crystallization and ablation for KrF laser (wavelength 248 nm) than for the XeCl laser (wavelength 308 nm). So, the possibility of the femtosecond and nanosecond laser pulses to crystallize a-Si films on non refractory glass substrates was shown. The results obtained are of great importance for manufacturing of polycrystalline silicon layers on non-refractory large-scale substrates for giant microelectronics.

scholarly journals Laser-impact-induced splashing: an analysis of the splash crown evolution after Nd:YAG ns-pulse laser impact on a liquid tin pool

2021 ◽  
Vol 127 (3) ◽  
Author(s):  
J. Hermens ◽  
H. Gelderblom ◽  
B. Liu ◽  
J. Duffhues ◽  
P. Rindt ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Extreme Ultraviolet ◽  
Laser Energy ◽  
Spot Size ◽  
Intense Laser ◽  
Expansion Velocity ◽  
Laser Fluences ◽  
Crown Width ◽  
Laser Impact ◽  
Liquid Tin

AbstractThe splash created by intense laser pulse impact onto a liquid tin layer is studied experimentally using time-delayed stroboscopic shadowgraphy. An 8-ns infrared (1064 nm) laser pulse is focused onto a deep liquid tin pool. Various laser spot sizes (70, 120, and 130 $$\upmu$$ μ m in diameter) and various laser pulse energies (ranging 2.5–30 mJ) are used, resulting in laser fluences of $$\sim$$ ∼  10–1000 J/cm$$^2$$ 2 inducing pronounced splashing. Specifically, we study the time evolution of the splash crown-width. The crown width expansion velocity is found to be linearly dependent on the laser energy, and independent of the focal spot size. A collapse of all crown width evolution data onto a single master curve confirms that the hydrodynamic evolution of our laser-impact-induced splash is equivalent to droplet-impact-induced splashing. Laser-impact splashing is particularly relevant, e.g. for high-brightness laser-assisted discharge-produced plasma and laser-produced plasma sources of extreme ultraviolet light for nanolithography.

Hole pattern formation in unfired ceramic sheets by pulsed Nd:YAG laser

1990 ◽  
Vol 5 (4) ◽  
pp. 841-846 ◽  
Author(s):  
Rong-Fuh Louh ◽  
Relva C. Buchanan
Keyword(s):  
Laser Pulse ◽  
Pulse Energy ◽  
Nd:Yag Laser ◽  
Laser Pulses ◽  
Spot Size ◽  
Single Shot ◽  
Radial Temperature ◽  
Laser Ceramic ◽  
Beam Spot Size ◽  
Before And After

Single shot pulses from a Nd:YAG laser have been used to generate different sized holes and patterns in unfired ceramic sheets for electronic packaging applications. The single shot laser pulses were targeted using a computer controlled deflection system and a programmed pattern. With changes in pulse energy level and profile, the laser beam was also used to sinter line patterns in deposited thin and thick films. The surface radial temperature profile resulting from the laser pulse interaction was also directly mapped using a lacquer thermocoat. Effects of the laser pulse energy and beam spot size on laser/ceramic interactions, morphology, and structure of the drilled holes before and after sintering were examined by SEM. High quality hole patterns (of ∼100 μm hole size) were produced in unfired 100 μm thick ceramic sheets up to 100 μm thick using single shot of laser irradiation with 8 mJ pulse energy and 18 nsec pulse duration.

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