Nonlinear absorption of a short intense laser pulse in a nonuniform plasma

The analytical solutions of nonlinear relativistic hydrodynamic equations for inhomogeneous plasmas are considered and the model of laser pulse absorption when the laser and plasma parameters are varied over a wide range of values is developed. The absorption coefficient has a local maxima at an optimal plasma density gradient for the given laser intensity, and that absorption then increases with scale length, in agreement with our particle-in-cell simulation results. The simulations and model have shown that the absorption of the foil target increases with laser intensity because of plasma density deepness and the spreading of the resonant area of laser plasma wave interaction.