The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
Wataru Masuda - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of q switched supersonic flow chemical oxygen iodine laser by solving time dependent Paraxial Wave Equation
Jsme International Journal Series B-fluids and Thermal Engineering, 2006Co-Authors: Masataro Suzuki, Hiroshi Matsueda, Wataru MasudaAbstract:The quality and power of an extracted beam from a Q-switched supersonic flow chemical oxygen-iodine laser have been investigated by numerical simulation. The flow system adopted in this study is the throat-mixing system proposed in a previous paper. Three-dimensional calculation for optics is coupled with one-dimensional calculation for gas flow including chemical reactions. Both geometric and Wave optics are calculated and compared to assess the effects of diffraction. Wave optics is calculated with a time-dependent Paraxial Wave Equation. The results indicate that Wave and geometric optics are qualitatively similar in the time-dependent behavior of beam power. Quantitatively, it is found that diffraction reduces the extracted power by 9%. It is also found from the spreading half-angle of the beam for Wave optics that the beam quality at a maximum power is equivalent to that of a plane Wave; however, it is lower than that of continuous extraction.
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numerical simulation of a q switched supersonic flow chemical oxygen iodine laser solving a time dependent Paraxial Wave Equation
XIV International Symposium on Gas Flow Chemical Lasers and High-Power Lasers, 2003Co-Authors: Masataro Suzuki, Hiroshi Matsueda, Wataru MasudaAbstract:Quality and power of the extracted beam from a Q-switched supersonic-flow chemical oxygen-iodine laser has been investigated by numerical simulation. The flow system adopted in this study is a throat mixing system proposed in the previous paper. The calculation code consists of two parts: one is a code for the gas flow and chemical reactions, and the other is that for the optics. Because of the difference of characteristic times between the phenomena in these two parts, every 300-time-steps of the latter calculation is coupled with one-time-step of the former. Both geometric and Wave optics are calculated in order to assess the effects of diffraction. The Wave optics is calculated with a Paraxial Wave Equation derived in this study. The results indicate that the time dependence of the beam power is qualitatively similar between the Wave and geometric optics. The peak power reaches to the maximum value at 90 ns after the initiation of oscillation. The peak value for the Wave optics is 9% less than that for the geometric optics. The calculated spreading angle of the beam shows that the laser quality at the maximum power is slightly worse compared to that of continuous extraction.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Masataro Suzuki - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of q switched supersonic flow chemical oxygen iodine laser by solving time dependent Paraxial Wave Equation
Jsme International Journal Series B-fluids and Thermal Engineering, 2006Co-Authors: Masataro Suzuki, Hiroshi Matsueda, Wataru MasudaAbstract:The quality and power of an extracted beam from a Q-switched supersonic flow chemical oxygen-iodine laser have been investigated by numerical simulation. The flow system adopted in this study is the throat-mixing system proposed in a previous paper. Three-dimensional calculation for optics is coupled with one-dimensional calculation for gas flow including chemical reactions. Both geometric and Wave optics are calculated and compared to assess the effects of diffraction. Wave optics is calculated with a time-dependent Paraxial Wave Equation. The results indicate that Wave and geometric optics are qualitatively similar in the time-dependent behavior of beam power. Quantitatively, it is found that diffraction reduces the extracted power by 9%. It is also found from the spreading half-angle of the beam for Wave optics that the beam quality at a maximum power is equivalent to that of a plane Wave; however, it is lower than that of continuous extraction.
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numerical simulation of a q switched supersonic flow chemical oxygen iodine laser solving a time dependent Paraxial Wave Equation
XIV International Symposium on Gas Flow Chemical Lasers and High-Power Lasers, 2003Co-Authors: Masataro Suzuki, Hiroshi Matsueda, Wataru MasudaAbstract:Quality and power of the extracted beam from a Q-switched supersonic-flow chemical oxygen-iodine laser has been investigated by numerical simulation. The flow system adopted in this study is a throat mixing system proposed in the previous paper. The calculation code consists of two parts: one is a code for the gas flow and chemical reactions, and the other is that for the optics. Because of the difference of characteristic times between the phenomena in these two parts, every 300-time-steps of the latter calculation is coupled with one-time-step of the former. Both geometric and Wave optics are calculated in order to assess the effects of diffraction. The Wave optics is calculated with a Paraxial Wave Equation derived in this study. The results indicate that the time dependence of the beam power is qualitatively similar between the Wave and geometric optics. The peak power reaches to the maximum value at 90 ns after the initiation of oscillation. The peak value for the Wave optics is 9% less than that for the geometric optics. The calculated spreading angle of the beam shows that the laser quality at the maximum power is slightly worse compared to that of continuous extraction.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
A V Volyar - One of the best experts on this subject based on the ideXlab platform.
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transverse shift of a high order Paraxial vortex beam induced by a homogeneous anisotropic medium
Physical Review A, 2009Co-Authors: Tatyana A Fadeyeva, A Rubass, A V VolyarAbstract:We have found the asymmetric splitting of a high-order circularly polarized vortex-beam in a uniaxial crystal. The l-order vortex-beam splits into the same one and the beam with the l-1 vortices at the beam axis while one optical vortex is shifted along the direction perpendicular to the inclination plane of the beam. Such a vortex displacement causes the transverse shift of the partial beam. We consider this effect both in terms of the conservation law of the angular-momentum flux and on the base of the solutions to the Paraxial Wave Equation. We revealed that the transverse shift of the crystal-traveling beam depends on neither a magnitude nor a sign of the vortex topological charge being defined only by a handedness of the initial circular polarization and a sign of the inclination angle of the beam.
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laguerre gaussian beams with complex and real arguments in a uniaxial crystal
Optics and Spectroscopy, 2006Co-Authors: A V Volyar, T A FadeevaAbstract:A solution to the Paraxial Wave Equation for Laguerre-Gaussian beams with complex and real arguments in a uniaxial crystal is found and analyzed. It is shown that the beams with a complex argument form a complete group of the solution, while the beams with a real argument satisfy the Equation only for an arbitrary radial index, with the azimuthal index being fixed and equal to l = 1. The evolution of phase singularities is considered by the example of transformation of the structure of topological multipoles and generation of optical vortices.
D F Farson - One of the best experts on this subject based on the ideXlab platform.
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co2 laser plume interaction in materials processing
Journal of Applied Physics, 2001Co-Authors: K R Kim, D F FarsonAbstract:In laser materials processing, localized evaporation caused by focused laser radiation forms a plume of mixed vapor and ambient gas above the material surface. The beam is refracted and absorbed as it traverses the plume, thus modifying its power density on the surface. In this work, plume–beam interaction is studied using an axisymmetric, high-temperature gas-dynamic model of a plume formed by vapor from an iron surface. The beam propagation in the plume is calculated from the Paraxial Wave Equation including absorption and refraction. The simulation results quantify the effects of plasma plume properties on the beam radius and laser power density variations at the material surface. It is shown that absorption and refraction in the plume have significant impacts on the laser–material interaction. Absorption of the beam in the plume has much less direct effect on the power density at the material surface than refraction does. However, absorption is essential for the formation of the plume, without which t...
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co2 laser plume interaction in materials processing
International Congress on Applications of Lasers & Electro-Optics, 2000Co-Authors: K R Kim, D F FarsonAbstract:In laser materials processing, localized evaporation caused by focused laser radiation results in a partially-ionized plume above the material surface. The beam is refracted and absorbed as it traverses the plume and these effects are of interest for process development. Here, plume-beam interactions are studied using an axisymmetric, high-temperature gasdynamic model of a plume formed by vapor from a flat iron surface. The beam propagation in the plume is calculated from the Paraxial Wave Equation including absorption and refraction. It is shown that absorption of the beam in the plume has much less direct effect on the power density at the material surface than refraction does. Helium gas is more efficient than argon for reducing the beam refraction and absorption effects. Laser energy reflected from the material surface has significant effects on the plume properties.In laser materials processing, localized evaporation caused by focused laser radiation results in a partially-ionized plume above the material surface. The beam is refracted and absorbed as it traverses the plume and these effects are of interest for process development. Here, plume-beam interactions are studied using an axisymmetric, high-temperature gasdynamic model of a plume formed by vapor from a flat iron surface. The beam propagation in the plume is calculated from the Paraxial Wave Equation including absorption and refraction. It is shown that absorption of the beam in the plume has much less direct effect on the power density at the material surface than refraction does. Helium gas is more efficient than argon for reducing the beam refraction and absorption effects. Laser energy reflected from the material surface has significant effects on the plume properties.
Carey Bunks - One of the best experts on this subject based on the ideXlab platform.
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effective filtering of artifacts for implicit finite difference Paraxial Wave Equation migration1
Geophysical Prospecting, 1995Co-Authors: Carey BunksAbstract:Implicit finite-difference implementations of the Paraxial Wave Equation are widely used in industrial prestack and post-stack migration programs for imaging and velocity analysis. This type of implementation gives rise to numerical artifacts which, in general, do not degrade image quality but which do impede effective velocity analysis. This paper reviews the artifacts generated by the Paraxial approximation and a post-extrapolation, spatially varying filtering scheme is described which completely eliminates these artifacts. The method is illustrated with numerous examples.
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filtering of numerical artifacts for Paraxial Wave Equation migration operators
55th EAEG Meeting, 1993Co-Authors: Carey BunksAbstract:The Paraxial Wave Equation is one of the most accurate pre-stack imaging tools for seismic data. It has been shown that pre-stack Paraxial Wave Equation migration correctly images seismic data even for very complex velocity models (e.g., such as those containing caustics [1]). Furthermore, since the Paraxial approximation gives rise to a one-way Wave Equation it is ideal for migration and imaging since, in principle, it does not generate reflections as do the acoustic and elastic Wave Equations. Nevertheless, the formulation and implementation of the Paraxial Wave Equation give rise to some undesirable numerical artifacts.
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effective filtering of artifacts for finite difference implementations of Paraxial Wave Equation migration
Seg Technical Program Expanded Abstracts, 1993Co-Authors: Carey BunksAbstract:The par-axial Wave Equation is one of the most accurate prestack imaging tools for seismic data. It has been shown that pre-stack par-axial Wave Equation migration correctly images seismic data even for very complex velocity models (e.g., such as those containing caustics [4]). Furthermore, since the Paraxial approximation gives rise to a one-way Wave Equation it is ideal for migration and imaging since, in principle, it does not generate reflections as do the acoustic and elastic Wave Equations. Nevertheless, the formulation and implementation of the Paraxial Wave Equation give rise to undesirable numerical artifacts [ 1], [3]. Some thought has already been given to the filtering of these artifacts by using complex coefficients in the rational approximation to the Paraxial Wave Equation [5]. This choice, however, only partially eliminates the artifacts and degrades the performance of the opening and amplitude responses of the par-axial operator. In this paper an efficient, post-extrapolation filtering scheme is described which completely eliminates the numerical artifacts while preserving the opening and amplitude characteristics of the Paraxial operator.
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Paraxial Wave Equation inversion with geometric constraints
54th EAEG Meeting, 1992Co-Authors: Carey BunksAbstract:The Paraxial Wave Equation is one of the most accurate pre-stack imaging tools for seismic data . It has been shown that pre-stack Paraxial Wave Equation migration correctly images seismic data even for very complex velocity models (such as those containing caustics). Furthermore, the fact that the Paraxial approximation yields a one-way Wave Equation is ideal for migration and imaging since in principle it does not generate reflections as do the acoustic and elastic Wave Equations. Nevertheless, the formulation and implementation of the Paraxial Wave Equation give rise to some undesirable numerical artifacts.
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optimization of Paraxial Wave Equation operator coefficients
Seg Technical Program Expanded Abstracts, 1992Co-Authors: Carey BunksAbstract:Paraxial Wave Equation migration is one of the most accurate pre-stack imaging techniques for complicated velocity models. Paraxial migration can image steep dips, however, there is a trade-off between the opening of the Paraxial operator and its associated computational cost. Consequently, it is of interest to optimize Paraxial Wave Equation operator coefficients o as to obtain as much opening as possible (within reasonable error) for the cost. In this paper optimal Paraxial Wave Equation operator coefficients are presented. These coefficients rue improvements over those found by others [l]. [3]. The performance of standard 4S’, 65 ‘, and optimized coefficients are compared analytical. Furthermore, numerical tests are performed which compare migrations of the Marmousi model based on these different coefficient sets.
