In the present paper, self-focusing of laser beams in relativistic plasmas is studied by the moment theory approach. The equilibrium beam radius of the self-trapped laser beams is also derived. Results are compared with the paraxial ray theory. It is observed from the analysis that at higher intensities, the equilibrium beam radius increases in case of the paraxial ray theory, whereas it becomes independent of the beam intensity in case of the moment theory. Analysis also confirms the role of relativistic electrons travelling with the light pulse in (3D PIC) simulation studies.
This paper presents an investigation of self-focusing of Gaussian laser beam in collisional plasma and its effect on second harmonic generation. Due to non-uniform heating, collisional non-linearity arises, which leads to redistribution of carriers and hence affects the plasma wave, which in turn affects the second harmonic generation. Effect of the intensity of the laser beam/plasma density on the harmonic yield is studied in detail. We have set up the non-linear differential equations for the beam width parameters of the main beam, plasma wave, second harmonic generation and second harmonic yield by taking full non-linear part of the dielectric constant of collisional plasma with the help of moment theory approach. It is predicted from the analysis that harmonic yield increases/decreases due to increase in the plasma density/intensity of the laser beam respectively.
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