Abstract
Theoretical investigation on optical self action effects of intense q-Gaussian laser beams interacting with collisionless plasmas with axial density ramp has been presented. Emphasis are put on investigating the dynamics of beam width and axial phase of the laser beam. Effect of the ellipticity of the cross section of the laser beam also has been incorporated. Using variational theory based on Lagrangian formulation nonlinear partial differential equation (P.D.E) governing the evolution of beam amplitude has been reduced to a set of coupled ordinary differential equations for the beam widths of the laser beam along the transverse directions. The evolution equation for the axial phase of the laser beam has been obtained by the Fourier transform of the amplitude structure of the laser beam from coordinate space to \((k_x, k_y)\) space. The differential equations so obtained have been solved numerically to envision the effect of laser-plasma parameters on the propagation dynamics of the laser beam.
Highlights
Laser[1] is the one of the most important scientific inventions of the 20th century
Using variational theory based on Lagrangian formulation nonlinear partial differential equation (P.D.E) governing the evolution of beam amplitude has been reduced to a set of coupled ordinary differential equations for the beam widths of the laser beam along the transverse directions
In conclusion we have presented the effects of both ellipticity of the cross section of the laser beam as well as the deviation of amplitude structure from ideal Gaussian profile on its nonlinear propagation characteristics
Summary
Laser[1] is the one of the most important scientific inventions of the 20th century. When laser made its debut, it was referred to as solution in search of a problem. Selftrapping occurs when self-focusing substantially exactly counteracts beam spreading due to diffraction When this happens, the cross section of the light induced channel remains substantially constant with propagation distance over the distance of the self-trapping. The relativistic nonlinearity immediately comes into picture when the power of incident laser exceeds the threshold required for self-focusing and it does not show any transient behaviour In this mechanism optical properties of plasma become a function of intensity of the electromagnetic beam due to change in electron mass when it starts oscillating at a velocity comparable to that of light. The modification of index of refraction occurs due to redistribution of electrons This time electrons migrate from the high intensity regions due to the temperature gradient produced by the laser beam in the illuminated portion of plasma. This paper aims to present theoretical investigation on self action effects of elliptical q-Gaussian laser beam in collisionless plasmas with axial density ramp
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