Collisionless absorption of femtosecond laser pulses in plasmas by nonlinear forces

Abstract

A mechanism has been discussed before by Dragila and Hora where very short laser pulses in a homogeneous plasma can be absorbed without collisions by the action of time dependent nonlinear forces. The resulting absorption lengths are of interest for the study of femtosecond neodymium glass laser pulses or the sub-picosecond carbon dioxide laser pulses which are now available. A mathematically more rigorous treatment of this problem is presented where a nonlinear differential equation is derived for the general solution in the approximation of Klima and Petrzilka. The ordinary differential equation can be solved exactly. With reasonable initial conditions, the solutions are similar to those of Dragila and Hora and are evaluated numerically for cases of experimental interest.