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1

Enhanced resonant second harmonic generation in plasma based on density transition

Kant N., Thakur V.

Nukleonika

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2015

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Vol. 60, No. 2

355--360

EN

Resonant second harmonic generation of a relativistic self-focusing laser in plasma with density ramp profile has been investigated. A high intense Gaussian laser beam generates resonant second harmonic beam in plasma with density ramp profile. The second harmonic undergoes periodic focusing in the plasma channel created by the fundamental wave. The normalized second harmonic amplitude varies periodically with distance and attains maximum value in the focal region. Enhancement in the second harmonic amplitude on account of relativistic self-focusing of laser based on plasma density transition is seen. Plasma density ramp plays an important role to make self-focusing stronger which leads to enhance the second harmonic generation in plasma.

2

Ponderomotive self-focusing of a short laser pulse under a plasma density ramp

Kant N., Saralch S., Singh H.

Nukleonika

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2011

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Vol. 56, No. 2

149-153

EN

The ponderomotive self-focusing of a short laser pulse in an underdense plasma under a plasma density ramp is analyzed. The pulse may acquire a minimum spot size due to the ponderomotive self-focusing. Beyond the focus, the nonlinear refraction starts weakening, and the spot size of the laser pulse increases, resulting in an oscillatory self-focusing and defocusing behavior of the beam with the propagation distance. In order to minimize the defocusing, we introduce a localized upward plasma density ramp. Due to the upward plasma density ramp, the laser beam retains a minimum spot size. Self-focusing becomes stronger with a mild ripple as the propagation distance increases. The conditions for the ponderomotive self-focusing for suitable parameters of the laser beam and the plasma are determined. The plasma density ramp of the considered type may be observed in gas jet plasma experiments.

3

Soliton pairing of two coaxially co-propagating mutually incoherent 1-D beams in Kerr type media.

Medhekar S., Sarkar K. R., Paltami P. P.

Optica Applicata

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2007

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Vol. 37, nr 3

243-259

EN

In this paper, we have developed a theory (using parabolic equation approach) of coupled propagation of two coaxially co-propagating and mutually incoherent bright 1-D beams in Kerr type media. We have provided a detailed account of the propagation behavior and condition of formation of spatial soliton pairs for various coupling coefficients ( = 1, 2/3, 2) when wavelengths and widths of the beams are the same/different. We have also identified conditions for a distinct type of coupled propagation. Our simple and straightforward theory presents many features of co-propagating beams which are in agreement with the features reported earlier using coupled nonlinear Schrödinger equation (NLSE). The paper adds to the understanding of coupled propagation by revealing many additional features not reported earlier.

4

Beam switching at a nonlinear-linear interface

Nasalski W.

Journal of Technical Physics

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2000

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Vol. 41, no 3

201-218

EN

Reflection of a beam incident front a nonlinear Kerr medium at a nonlinear-linear dielectric interface is analysed for incidence close to the critical angle of total internal reflection. The problem is formulated and solved within the frame of a reduced variational technique. The solution obtained is interpreted in terms of aberrationless effects of nonlinear propagation and nonspecular effects of nonlinear reflection. A bistable switch in the reflected beam power, waist position and diameter, as well as in the beam ais direction, is demonstrated. A position of a bistable loop indicates that the nature of the switch is qualitatively different from that predicted by the plane wave analysis. It is shown that these differences result from self-focusing of the incident and reflected beams, their mutual cross-phase modulation and large nonspecular deformations of the reflected beam.