ANOMALOUS ABSORPTION AND SCATTERING OF SHORT-PULSE HIGH-INTENSITY LASERS IN UNDERDENSE PLASMAS

The propagation of short-pulse lasers through several Rayleigh lengths of underdense plasma [(1-4)% n(cr)] is studied using multidimensional fully explicit particle-in-cell simulations. The simulations model 80 to 600 fs, 1 mu m wavelength pulses in the intensity range of 1.5 x 1 0(17) to 3.5 X 10(19) W/cm2. A detailed account is given for the energ y lost out of the focal cone due to a combination of collective absorp tion and scattering losses. The figure of merit for the nonlinear tran smission losses of a given pulse length is the amount of Raman forward scattering exponentiation within a Rayleigh length.