One-dimensional simulations of ultrashort intense laser pulses on solid-density targets

Presented are simulations in one dimension of laser pulses with a pre-ionized thin target. The duration of the laser pulse is between 10 and 200 fs, the laser power is between 1018 and 1022 W/cm2, and the wavelength is 400 nm. The targets were foils of either aluminum at normal density, or in a few cases plastic (chemical formula CH) at a density of 1.1 g/cm3, and varied from 20 to 4000 nm in thickness. The simulation results show that at these intensities the absorption mechanism for a normally incident pulse changes to a collisionless mechanism first proposed by Kruer and Estabrook [W. L. Kruer and K. Estabrook, Phys. Fluids 28, 430 (1985)]. Use of a thin target ensures that the energy imparted to the electrons will be electrostatically transferred to the ions rather than transported for large distances into the target.