The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Mitsuhiro Tateda - One of the best experts on this subject based on the ideXlab platform.
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efficient self pumped phase conjugation with a Loop Geometry in a rhodamine 6g solid dye laser amplifier
Optics Express, 2003Co-Authors: H. Watanabe, Takashige Omatsu, Mitsuhiro TatedaAbstract:We present what to our knowledge is the first demonstration of self-pumped phase conjugation in a laser-pumped solid-state Rhodamine-6G dye saturable amplifier. Phase-conjugate energy reflectivity of as much as 2100% at 557 nm has been obtained.
M Selwa - One of the best experts on this subject based on the ideXlab platform.
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the role of active region Loop Geometry ii symmetry breaking in three dimensional active region why are vertical kink oscillations observed so rarely
The Astrophysical Journal, 2011Co-Authors: M Selwa, L Ofman, S K SolankiAbstract:We present numerical results of simulations of kink oscillations of coronal Loops in an idealized active region (AR) that is initialized as a potential dipole magnetic configuration with gravitationally stratified density. We consider Loops, with density higher than the surrounding plasma, embedded into the dipolar AR. We study the excitation of kink oscillations of such Loops by velocity pulses at different positions, of a given duration and amplitude. The position of the pulse varies in the parametric studies. For a central (symmetric) Loop within the AR, we find that the amplitude of vertical kink oscillations is significantly amplified in comparison to horizontal kink oscillations for exciters located centrally (symmetrically) below the Loop. For pulses initiated further from such a symmetric Loop a combination of vertical and horizontal oscillations is excited. The scenario changes significantly when we study an inclined Loop (non-symmetric within a dipole field). In this case, we do not see vertical kink oscillations of any significant amplitude being excited, while horizontal ones can be easily detected. These results indicate that the reason why vertical kink oscillations are observed so rarely is that their excitation requires a set of conditions to occur simultaneously: the exciting pulse must be located roughly below the Loop apex and the Loop itself must be located symmetrically within the group of Loops. The new findings of the present study show the importance of not only the position of the pulse, but mainly of the location of the Loop within the set of field lines having the same magnetic connectivity. We find that the slow propagating wave is excited in all the studied Loops and its excitation does not depend either on the Geometry of the Loop or the pulse. We discuss TRACE observations of coronal Loop oscillations in view of our findings and find that our results can be used for identifying the polarization of the kink mode based on the location of the Loop within the set of field lines of the same connectivity and the position of the flare.
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the role of active region Loop Geometry i how can it affect coronal seismology
The Astrophysical Journal, 2011Co-Authors: M Selwa, L Ofman, S K SolankiAbstract:We present numerical results of coronal Loop oscillation excitation using a three-dimensional (3D) MHD model of an idealized active region (AR) field. The AR is initialized as a potential dipole magnetic configuration with gravitationally stratified density and contains a Loop with a higher density than its surroundings. We study different ways of excitation of vertical kink oscillations of this Loop by velocity: as an initial condition, and as an impulsive excitation with a pulse of a given position, duration, and amplitude. We vary the Geometry of the Loop in the 3D MHD model and find that it affects both the period of oscillations and the synthetic observations (difference images) that we get from oscillations. Due to the overestimated effective length of the Loop in the case of Loops which have maximum separation between their legs above the footpoints (>50% of observed Loops), the magnetic field obtained from coronal seismology can also be overestimated. The 3D MHD model shows how the accuracy of magnetic field strength determined from coronal seismology can be improved. We study the damping mechanism of the oscillations and find that vertical kink waves in 3D stratified Geometry are damped mainly due to wave leakage in the horizontal direction.
M J Damzen - One of the best experts on this subject based on the ideXlab platform.
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Characterization of a distortion-corrected Nd:YAG laser with a self-conjugating Loop Geometry
IEEE Journal of Quantum Electronics, 1999Co-Authors: O. Wittler, G J Crofts, D. Udaiyan, K.s. Syed, M J DamzenAbstract:A detailed experimental and theoretical characterization of a self-adaptive solid-state laser is presented. The system uses a saturable gain medium (Nd:YAG amplifier) as the adaptive element in an externally injected self-intersecting Loop Geometry. We demonstrate energy output >300 mJ, high energy reflectivity >10/sup 4/, low input energy threshold of /spl sim/5 /spl mu/J, and phase-conjugate properties of the system that compensate for both intracavity and extracavity phase distortions. The spatial output beam size is compared to a Gaussian mode analysis based on ABCD ray transfer matrices. The temporal, spectral, energy, and threshold characteristics are compared to one-dimensional analytical and transient numerical simulations.
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reflectivity and oscillation conditions of a gain medium in a self conjugating Loop Geometry
Optics Letters, 1994Co-Authors: M J Damzen, R P M Green, G J CroftsAbstract:The intensity-dependent reflectivity of a gain medium in a self-phase-conjugating Loop Geometry is numerically modeled by use of exact integration equations without restriction on the degree of gain saturation. High conjugate reflectivity and high energy extraction efficiency of the gain medium are predicted. A weak saturation analysis is also presented to derive useful expressions for the threshold input intensity for oscillation of the backward conjugate mode and the resonant oscillation frequencies.
H. Watanabe - One of the best experts on this subject based on the ideXlab platform.
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Self-pumped phase conjugation with a Rhodamine 6G solid laser dye saturable amplifier
2003 Conference on Lasers and Electro-Optics Europe (CLEO Europe 2003) (IEEE Cat. No.03TH8666), 2003Co-Authors: H. Watanabe, T. OmatsuAbstract:In this paper, we have demonstrated, self-pumped phase conjugation with a self-intersecting Loop Geometry in a Rhodamine-6G solid laser dye saturable amplifier pumped by a frequency-doubled Nd:YAG laser. The maximum phase conjugate reflectivity of 2100% was obtained at 557 nm. The maximum output energy was 71 /spl mu/J.
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efficient self pumped phase conjugation with a Loop Geometry in a rhodamine 6g solid dye laser amplifier
Optics Express, 2003Co-Authors: H. Watanabe, Takashige Omatsu, Mitsuhiro TatedaAbstract:We present what to our knowledge is the first demonstration of self-pumped phase conjugation in a laser-pumped solid-state Rhodamine-6G dye saturable amplifier. Phase-conjugate energy reflectivity of as much as 2100% at 557 nm has been obtained.
L Ofman - One of the best experts on this subject based on the ideXlab platform.
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the role of active region Loop Geometry ii symmetry breaking in three dimensional active region why are vertical kink oscillations observed so rarely
The Astrophysical Journal, 2011Co-Authors: M Selwa, L Ofman, S K SolankiAbstract:We present numerical results of simulations of kink oscillations of coronal Loops in an idealized active region (AR) that is initialized as a potential dipole magnetic configuration with gravitationally stratified density. We consider Loops, with density higher than the surrounding plasma, embedded into the dipolar AR. We study the excitation of kink oscillations of such Loops by velocity pulses at different positions, of a given duration and amplitude. The position of the pulse varies in the parametric studies. For a central (symmetric) Loop within the AR, we find that the amplitude of vertical kink oscillations is significantly amplified in comparison to horizontal kink oscillations for exciters located centrally (symmetrically) below the Loop. For pulses initiated further from such a symmetric Loop a combination of vertical and horizontal oscillations is excited. The scenario changes significantly when we study an inclined Loop (non-symmetric within a dipole field). In this case, we do not see vertical kink oscillations of any significant amplitude being excited, while horizontal ones can be easily detected. These results indicate that the reason why vertical kink oscillations are observed so rarely is that their excitation requires a set of conditions to occur simultaneously: the exciting pulse must be located roughly below the Loop apex and the Loop itself must be located symmetrically within the group of Loops. The new findings of the present study show the importance of not only the position of the pulse, but mainly of the location of the Loop within the set of field lines having the same magnetic connectivity. We find that the slow propagating wave is excited in all the studied Loops and its excitation does not depend either on the Geometry of the Loop or the pulse. We discuss TRACE observations of coronal Loop oscillations in view of our findings and find that our results can be used for identifying the polarization of the kink mode based on the location of the Loop within the set of field lines of the same connectivity and the position of the flare.
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the role of active region Loop Geometry i how can it affect coronal seismology
The Astrophysical Journal, 2011Co-Authors: M Selwa, L Ofman, S K SolankiAbstract:We present numerical results of coronal Loop oscillation excitation using a three-dimensional (3D) MHD model of an idealized active region (AR) field. The AR is initialized as a potential dipole magnetic configuration with gravitationally stratified density and contains a Loop with a higher density than its surroundings. We study different ways of excitation of vertical kink oscillations of this Loop by velocity: as an initial condition, and as an impulsive excitation with a pulse of a given position, duration, and amplitude. We vary the Geometry of the Loop in the 3D MHD model and find that it affects both the period of oscillations and the synthetic observations (difference images) that we get from oscillations. Due to the overestimated effective length of the Loop in the case of Loops which have maximum separation between their legs above the footpoints (>50% of observed Loops), the magnetic field obtained from coronal seismology can also be overestimated. The 3D MHD model shows how the accuracy of magnetic field strength determined from coronal seismology can be improved. We study the damping mechanism of the oscillations and find that vertical kink waves in 3D stratified Geometry are damped mainly due to wave leakage in the horizontal direction.
