scholarly journals Simulation of femtosecond laser absorption by metallic targets and their thermal evolution

2017 ◽  
Vol 35 (3) ◽  
pp. 415-428 ◽  
Author(s):  
A. Suslova ◽  
A. Hassanein
Keyword(s):  
Femtosecond Laser ◽  
Laser Intensity ◽  
Laser Energy ◽  
Absorption Efficiency ◽  
Optical Parameters ◽  
Temperature Dependent ◽  
Simulation Code ◽  
Laser Absorption ◽  
Plasma State ◽  
Wide Range

AbstractThe interaction of femtosecond laser with initially cold solid metallic targets (Al, Au, Cu, Mo, Ni) was investigated in a wide range of laser intensity with focus on the laser energy absorption efficiency. Our developed simulation code (FEMTO-2D) is based on two-temperature model in two-dimensional configuration, where the temperature-dependent optical and thermodynamic properties of the target material were considered. The role of the collisional processes in the ultrashort pulse laser–matter interaction has been carefully analyzed throughout the process of material transition from the cold solid state into the dense plasma state during the pulse. We have compared the simulation predictions of the laser pulse absorption with temperature-dependent reflectivity and optical penetration depth to the case of constant optical parameters. By considering the effect of the temporal and spatial (radial) distribution of the laser intensity on the light absorption efficiency, we obtained a good agreement between the simulated results and available experimental data. The appropriate model for temperature-dependent optical parameters defining the laser absorption efficiency will allow more accurate simulation of the target thermal response in the applications where it is critical, such as prediction of the material damage threshold, laser ablation threshold, and the ablation profile.

scholarly journals A relativistic PIC model of nonlinear laser absorption in a finite-size plasma with arbitrary mass and density ratios

2015 ◽  
Vol 33 (4) ◽  
pp. 647-654 ◽  
Author(s):  
H. Mehdian ◽  
A. Kargarian ◽  
A. Hasanbeigi ◽  
K. Hajisharifi
Keyword(s):  
Laser Energy ◽  
Density Ratio ◽  
Finite Size ◽  
Intense Laser ◽  
Equilibrium Density ◽  
Nonlinear Phenomena ◽  
Simulation Code ◽  
Laser Scattering ◽  
Laser Absorption ◽  
Density Ratios

AbstractIn this paper, we have studied the nonlinear laser absorption in a finite-size plasma, using a fully kinetic relativistic 1½-dimensional particle-in-cell simulation code, and shown that the rate in which laser absorption increases depends on the mass ratio (δ = m+/m−) and the equilibrium density ratio (α = n0+/n0− = z−/z+), respectively. This can be attributed to the essential effects of these parameters on the nonlinear phenomena related to the laser absorption such as phase-mixing and laser-scattering process. We have indicated that the reduction of the defined mass and density ratios increases the absorption rate in the finite-size plasma as long as the laser scattering from the plasma is not considerable. Moreover, the study of kinetic phase-space distributions indicates in a specific range of mass and density ratios a large amount of laser energy leads to arise a population of charged particles having directed kinetic energy along the laser direction. These simulation results are expected to be relevant to the experiments on the intense laser–plasma interactions with applications to the particle acceleration and fast ignition concept as well as to the astrophysical environments.

scholarly journals Nonlinear laser absorption over a dielectric embedded with nanorods

2019 ◽  
Vol 37 (4) ◽  
pp. 381-385
Author(s):  
Soni Sharma ◽  
A. Vijay
Keyword(s):  
Laser Intensity ◽  
Plasma Frequency ◽  
Laser Energy ◽  
Dielectric Surface ◽  
Space Charge Field ◽  
Free Electrons ◽  
Laser Absorption ◽  
Oscillatory Velocity ◽  
Planar Array ◽  
Charge Field

AbstractAn analytical formalism of laser absorption in a nanorod embedded dielectric surface has been developed. Nanorods lie in the plane of the dielectric, in the form of a planar array. A laser, impinged on them with an electric field perpendicular to the lengths of the nanorods, imparts oscillatory velocity to nanorod electrons. As the free electrons of a nanorod are displaced, a space charge field is developed in the nanorod that exerts restoration force on the electrons and their drift velocity shows a resonance at ${\rm \omega} = {\rm \omega} _{\rm p}/\sqrt 2 $, where ωp denotes the plasma frequency of free electrons inside the nanorod. It is inhibited by collisions and nanorod expansion. At the resonance, the electrons are efficiently heated by the laser and laser energy is strongly absorbed, resulting in significant reduction in laser transmissivity. The transmissivity decreases with laser intensity.

Temperature Dependent Kinetics of the OH/HO2/O3Chain Reaction by Time-Resolved IR Laser Absorption Spectroscopy

2000 ◽  
Vol 104 (17) ◽  
pp. 3964-3973 ◽  
Author(s):  
Sergey A. Nizkorodov ◽  
Warren W. Harper ◽  
Bradley W. Blackmon ◽  
David J. Nesbitt
Keyword(s):  
Absorption Spectroscopy ◽  
Laser Absorption Spectroscopy ◽  
Temperature Dependent ◽  
Time Resolved ◽  
Laser Absorption ◽  
Ir Laser ◽  
Kinetics Of

scholarly journals Study and Assessment of Defect and Trap Effects on the Current Capabilities of a 4H-SiC-Based Power MOSFET

Electronics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 735
Author(s):  
Fortunato Pezzimenti ◽  
Hichem Bencherif ◽  
Giuseppe De Martino ◽  
Lakhdar Dehimi ◽  
Riccardo Carotenuto ◽  
...  
Keyword(s):  
Drain Current ◽  
Oxide Semiconductor ◽  
Temperature Dependent ◽  
Channel Mobility ◽  
Blocking Voltage ◽  
Current Voltage ◽  
Wide Range ◽  
Temperature Ranges ◽  
Joint Contribution ◽  
State Resistance

A numerical simulation study accounting for trap and defect effects on the current-voltage characteristics of a 4H-SiC-based power metal-oxide-semiconductor field effect transistor (MOSFET) is performed in a wide range of temperatures and bias conditions. In particular, the most penalizing native defects in the starting substrate (i.e., EH6/7 and Z1/2) as well as the fixed oxide trap concentration and the density of states (DoS) at the 4H-SiC/SiO2 interface are carefully taken into account. The temperature-dependent physics of the interface traps are considered in detail. Scattering phenomena related to the joint contribution of defects and traps shift the MOSFET threshold voltage, reduce the channel mobility, and penalize the device current capabilities. However, while the MOSFET on-state resistance (RON) tends to increase with scattering centers, the sensitivity of the drain current to the temperature decreases especially when the device is operating at a high gate voltage (VGS). Assuming the temperature ranges from 300 K to 573 K, RON is about 2.5 MΩ·µm2 for VGS > 16 V with a percentage variation ΔRON lower than 20%. The device is rated to perform a blocking voltage of 650 V.

scholarly journals Diagnostic Capabilities of a Smartphone- Based Low-Cost Microscope

2020 ◽  
Vol 6 (3) ◽  
pp. 522-525
Author(s):  
Dorina Hasselbeck ◽  
Max B. Schäfer ◽  
Kent W. Stewart ◽  
Peter P. Pott
Keyword(s):  
Low Cost ◽  
Field Of View ◽  
Parasitic Diseases ◽  
Optical Parameters ◽  
Trade Off ◽  
Resource Limited ◽  
Wide Range ◽  
Diagnostic Applications ◽  
Diagnostic Capabilities

AbstractMicroscopy enables fast and effective diagnostics. However, in resource-limited regions microscopy is not accessible to everyone. Smartphone-based low-cost microscopes could be a powerful tool for diagnostic and educational purposes. In this paper, the imaging quality of a smartphone-based microscope with four different optical parameters is presented and a systematic overview of the resulting diagnostic applications is given. With the chosen configuration, aiming for a reasonable trade-off, an average resolution of 1.23 μm and a field of view of 1.12 mm2 was achieved. This enables a wide range of diagnostic applications such as the diagnosis of Malaria and other parasitic diseases.

Simplified coupling power model for fibers fusion

2009 ◽  
Vol 17 (3) ◽  
Author(s):  
J. Saktioto ◽  
J. Ali ◽  
M. Fadhali
Keyword(s):  
Refractive Index ◽  
Propagation Constant ◽  
Tunable Filter ◽  
Experimental Result ◽  
Total Power ◽  
Optical Parameters ◽  
Coupling Region ◽  
Ratio Distribution ◽  
Hydrogen Flow ◽  
Wide Range

AbstractFiber coupler fabrication used for an optical waveguide requires lossless power for an optimal application. The previous research coupled fibers were successfully fabricated by injecting hydrogen flow at 1 bar and fused slightly by unstable torch flame in the range of 800–1350°C. Optical parameters may vary significantly over wide range physical properties. Coupling coefficient and refractive index are estimated from the experimental result of the coupling ratio distribution from 1% to 75%. The change of geometrical fiber affects the normalized frequency V even for single mode fibers. V is derived and some parametric variations are performed on the left and right hand side of the coupling region. A partial power is modelled and derived using V, normalized lateral phase constant u, and normalized lateral attenuation constant, w through the second kind of modified Bessel function of the l order, which obeys the normal mode and normalized propagation constant b. Total power is maintained constant in order to comply with the energy conservation law. The power is integrated through V, u, and w over the pulling length of 7500 µm for 1-D. The core radius of a fiber significantly affects V and power partially at coupling region rather than wavelength and refractive index of core and cladding. This model has power phenomena in transmission and reflection for an optical switch and tunable filter.

Hydrogenation of methylacetylene. III. The reaction of methylacetylene with hydrogen catalyzed by nickel, copper, and their alloys

1968 ◽  
Vol 46 (4) ◽  
pp. 623-633 ◽  
Author(s):  
R. S. Mann ◽  
K. C. Khulbe
Keyword(s):  
Activation Energy ◽  
Nickel Catalyst ◽  
Hydrogen Pressure ◽  
Constant Volume ◽  
Temperature Dependent ◽  
Nickel Copper ◽  
Wide Range ◽  
Initial Hydrogen Pressure

The reaction between methylacetylene and hydrogen over unsupported nickel, copper, and their alloys has been investigated in a static constant volume system between 20 and 220 °C for a wide range of reactant ratios. The order of reaction with respect to hydrogen was one and nearly independent of temperature. While the order of reaction with respect to methylacetylene over nickel catalyst was slightly negative and temperature dependent, it was always positive and nearly independent of temperature for copper and copper-rich alloys. Selectivity was independent of initial hydrogen pressure for nickel and copper only; for others it decreased rapidly with increasing hydrogen pressure. The overall activation energy varied between 9 and 21.2 kcal/g mole. Selectivity and extent of polymerization increased with increasing amount of copper in the alloy.

PZT Film and Si Substrate Two-Layer System Patterning Morphology by Femtosecond Pulsed Laser

2007 ◽  
Author(s):  
Shizhou Xiao ◽  
Rui Guo ◽  
Guanghua Cheng ◽  
Yalei Wu ◽  
Wenhao Huang ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Energy ◽  
Threshold Model ◽  
Pulsed Laser ◽  
Direct Writing ◽  
Si Substrate ◽  
Layer System ◽  
Substrate Heating ◽  
Pzt Film ◽  
Femtosecond Pulsed Laser

In this paper, a novel PZT film patterning method by femtosecond laser is proposed. The method is different from traditional dry-etching and wet-etching technology. Femtosecond laser microfabrication technology has several advantages such as high resolution, no mask direct-writing and seldom-heating, etc. A two-layer (PZT thin film and substrate) heating and ablating threshold model is built and the relationship of PZT/Si two-layer system micro ablation morphology depending on laser pulse energy is constructed. From the model and experiment data, we obtain the suitable energy region to pattern PZT film freely without damage Si substrate. A 3μm resolution of PZT pattern is achieved in our experiment. In order to verify the fabrication available of this technology, several micro functional devices are successfully patterned by optimized femtosecond pulsed laser energy and their function are detected. The results prove that the PZT patterning quality is good.

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