The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Pradeep K. Gupta - One of the best experts on this subject based on the ideXlab platform.
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Waveguiding effect on optical spatial solitons in centrosymmetric photorefractive materials
Journal of Optics, 2017Co-Authors: Binay P. Akhouri, Pradeep K. GuptaAbstract:Photorefractive solitons have been studied in a waveguide that is made of centrosymmetric material. The dynamical equations pertaining to characteristics of solitons have been derived under Paraxial Ray and Wentzel–Kramers–Brillouin (WKB) approximations. It has been predicted that the planar waveguide structure enhances self-focusing effect and reduces the threshold power requirement for soliton formation. The waveguide that is embedded in the photorefractive crystal leads to the trapping of low power solitary wave which otherwise would not have formed spatial solitons at this low power in this material. The minimum requirement of power for self-trapping in the material decreases with the increase in the value of waveguide co-efficient. The existence of bistable states has also been predicted.
C Spencer - One of the best experts on this subject based on the ideXlab platform.
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a unified approach to Ray bending Ray perturbation and Paraxial Ray theories
Geophysical Journal International, 1993Co-Authors: Roel Snieder, C SpencerAbstract:SUMMARY In the past, perturbation theory has been formulated for the case that either a slowness model was perturbed and the effect of this perturbation on Rays was determined, or for the case where the slowness was fixed and where estimates of the Ray position were deformed towards the true Ray. In this paper both problems are combined in a single perturbation theory. The theory also accommodates arbitrary perturbations to the endpoints of Rays and leads to a simple linear differential equation for the Ray perturbation. Expressions are derived for the second-order perturbation of the traveltime. This quantity describes the effect of the Ray perturbation on the traveltime and of the bias in the traveltime due to the fact that the reference curve need not be a true Ray. The second-order traveltime perturbation can be evaluated efficiently by a single integration along the reference curve. In contrast to formalisms using Ray-centred coordinates, endpoints perturbations in an arbitrary direction are allowed. This is of importance in tomographic inversions which incorporate earthquake relocations. The cross-term between the slowness perturbations and the source relocations is derived explicitly. The fact that the reference curve does not need to be a true Ray in the reference medium allows for an iterative application of Ray perturbation theory. The use of the second-order traveltime perturbation allows one to correct for the bias in the traveltime due to the fact that the reference curve is not a Ray. A proof is given that the equation for the Ray perturbation is consistent with earlier results derived in Ray-centred coordinates and the relation with the Ray bending theory of Julian & Gubbins (1977) is established. For a fixed-slowness model and for fixed-Ray endpoints the two theories are equivalent except at isolated points, this is illustrated with an analogy from classical mechanics. This difference, which results in superior numerical properties for the new algorithm, is illustrated by several numerical examples.
Ranju Mahajan - One of the best experts on this subject based on the ideXlab platform.
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propagation of high power electromagnetic beam in relativistic magnetoplasma higher order Paraxial Ray theory
Physics of Plasmas, 2010Co-Authors: Tarsem Singh Gill, Ravinder Kaur, Ranju MahajanAbstract:This paper presents an analysis of self-consistent, steady-state, theoretical model, which explains the ring formation in a Gaussian electromagnetic beam propagating in a magnetoplasma, characterized by relativistic nonlinearity. Higher order terms (up to r4) in the expansion of the dielectric function and the eikonal have been taken into account. The condition for the formation of a dark and bright ring derived earlier by Misra and Mishra [J. Plasma Phys. 75, 769 (2009)] has been used to study focusing/defocusing of the beam. It is seen that inclusion of higher order terms does significantly affect the dependence of the beam width on the distance of propagation. Further, the effect of the magnetic field and the nature of nonlinearity on the ring formation and self-focusing of the beam have been explored.
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Growth of high power laser ripple in plasma and its effects on upper hybrid wave excitation: Relativistic effects
2008 IEEE 35th International Conference on Plasma Science, 2008Co-Authors: Tarsem Singh Gill, Nareshpal Singh Saini, Ranju MahajanAbstract:The growth of a radially symmetric ripple superimposed on a single intense Gaussian laser beam in a collisionless magnetized plasma is investigated. WKB and Paraxial Ray approximations are used to calculate wave equation for the main beam and the ripple. Numerical results show that the relativistic power of laser beam, the dynamics of ripple gets affected by its position and phase angle as well as some other parameters. The effect of growth of ripple on excitation of upper hybrid wave is also studied.
John C Howell - One of the best experts on this subject based on the ideXlab platform.
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Paraxial Ray optics cloaking
Optics Express, 2014Co-Authors: Joseph S Choi, John C HowellAbstract:Despite much interest and progress in optical spatial cloaking, a three-dimensional (3D), transmitting, continuously multidirectional cloak in the visible regime has not yet been demonstrated. Here we experimentally demonstrate such a cloak using Ray optics, albeit with some edge effects. Our device requires no new materials, uses isotropic off-the-shelf optics, scales easily to cloak arbitrarily large objects, and is as broadband as the choice of optical material, all of which have been challenges for current cloaking schemes. In addition, we provide a concise formalism that quantifies and produces perfect optical cloaks in the small-angle (‘Paraxial’) limit.
Binay P. Akhouri - One of the best experts on this subject based on the ideXlab platform.
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Waveguiding effect on optical spatial solitons in centrosymmetric photorefractive materials
Journal of Optics, 2017Co-Authors: Binay P. Akhouri, Pradeep K. GuptaAbstract:Photorefractive solitons have been studied in a waveguide that is made of centrosymmetric material. The dynamical equations pertaining to characteristics of solitons have been derived under Paraxial Ray and Wentzel–Kramers–Brillouin (WKB) approximations. It has been predicted that the planar waveguide structure enhances self-focusing effect and reduces the threshold power requirement for soliton formation. The waveguide that is embedded in the photorefractive crystal leads to the trapping of low power solitary wave which otherwise would not have formed spatial solitons at this low power in this material. The minimum requirement of power for self-trapping in the material decreases with the increase in the value of waveguide co-efficient. The existence of bistable states has also been predicted.
