The effect of the non-relativistic ponderomotive force in the interaction of an intense laser pulse with isothermal and non-isothermal underdense collisional plasmas is studied. In this work by considering the ohmic heating of plasma electrons and the ponderomotive force, the nonlinear dielectric permittivity of the plasma medium is obtained and the equation of electromagnetic wave propagation is solved. It is shown that due to the effect of the ponderomotive force in both isothermal and non-isothermal plasmas, the increasing of laser pulse intensity leads to the steepening of the electron density profile and the narrowing of electron bunching. Since the ponderomotive force modifies the electron density and temperature distribution, the spatial damping rate of laser energy and the absorption coefficient are obtained in the collisional regime of isothermal and non-isothermal plasmas. It is shown that in these plasmas, the amplitude of the electric field is increased by increasing laser pulse energy while their wavelength is decreased. Furthermore, by increasing laser pulse intensity, the absorption coefficient is decreased strongly.
Laser–plasma interaction studies in the context of shock ignition: the regime dominated by parametric instabilities