Numerical Investigation of the Ponderomotive Force Effect in an Underdense Plasma With a Linear Density Profile

In this paper, the nonlinear interaction between a high intense laser pulse and an unmagnetized underdense plasma with a linear density profile is investigated. Considering the inhomogeneity of the medium and ponderomotive nonlinearity, the nonlinear dielectric permittivity of the plasma is found. Then, using the dielectric permittivity and Maxwell´s equations, the nonlinear differential equations for the electric and magnetic fields in plasma are obtained. The solution of these equations shows that, by increasing the intensity of laser pulse, the wavelength of oscillations decreases and the electron density profile becomes a highly peaked structure. Finally, it is shown that the amplitude of electron density distribution decreases by increasing the laser wavelength.