Collisionless absorption of femtosecond laser pulses in plasmas by nonlinear forces

A mechanism for the collisionless absorption of femtosecond laser pulses in plasmas by nonlinear forces has been discussed by Dragila and Hora (1982). Here, a mathematically more rigorous treatment of the problem is presented, based on an exact solution to the nonlinear differential equation of Klima and Petrzilka (1978). On the basis of the analytical treatment, the variation of absorption length with the peak intensity of a neodymium glass laser pulse (wavelength = 1.06 microns) is computed for different pulse lengths in plasmas with densities of 90 and 99 percent of the critical density, respectively. The computed results are given in graphic form.