Excitation of ion acoustic waves by Laguerre−Gaussian laser beams in collisionless plasma: combined effects of self focusing and density ramp

Theoretical investigation has been conducted on the dynamics of ion acoustic waves (IAWs) excited by Laguerre-Gaussian laser beams in plasmas featuring an axial density ramp. The study incorporates an analysis of the impact of self-focusing of the laser beam on the power of the laser-excited IAWs. As the laser beam propagates through the plasma, it triggers the generation of an IAW at the frequency \(\omega_{ia}\) ${\omega }_{\mathit{ia}}$ . This IAW, influenced by the optical nonlinearity of the plasma, becomes nonlinearly coupled to the laser beam. Utilizing variational theory, semi-analytical solutions for the coupled nonlinear wave equations governing the pump wave and IAW have been derived under the W.K.B approximation technique. The findings indicate a significant influence of the self-focusing effect of the pump beam on the power of the IAW.