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 $\left[\right(1–4\left)\%n_{\mathrm{cr}}\right]$ is studied using multidimensional fully explicit particle-in-cell simulations. The simulations model 80 to 600 fs, 1 μm wavelength pulses in the intensity range of $1.5\times {10}^{17}$ to $3.5\times {10}^{19}$ W/c${\mathrm{m}}^2$. A detailed account is given for the energy lost out of the focal cone due to a combination of collective absorption and scattering losses. The figure of merit for the nonlinear transmission losses of a given pulse length is the amount of Raman forward scattering exponentiation within a Rayleigh length.