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Generation of Second Harmonics of q-Gaussian Laser Beams in Collisionless Plasma with Axial Density Ramp
Naveen Gupta and Sandeep Kumar

An investigation on frequency up conversion of laser beam through the phenomenon of second harmonic generation (SHG) in collisionless plasma with axial density ramp has been presented. Variational method has been adopted to find semi analytical solution of the wave equation for the slowly varying envelope of the laser beam. When laser beam with frequency ω0 propagates through plasma it makes the plasma electrons to oscillate at pump frequency ω0. These oscillations of the plasma electrons in the presence of thermal velocity generate an electron plasma wave (EPW) at frequency ω0. The generated EPW beats with the pump beam to produce its second harmonics. By using fluid model of plasma, nonlinear current density for SHG has been obtained. Emphasis are put on investigation of the effect of various laser and plasma parameters on propagation dynamics of pump beam and conversion efficiency of second harmonics.

Keywords: q-Gaussian, Density Ramp, Collisionless Plasma, Self Focusing, Harmonic Generation.