Absorption of high-intensity subpicosecond lasers on solid density targets

The absorption of subpicosecond (∼100 fs) high-intensity (I∼1020--1021 W/cm2) laser pulses normally incident on solid density targets is examined by particle simulations, which include electron scattering. For targets which are overdense by factors exceeding 100, electrons accelerated by the ponderomotive force of the laser couple their energy electrostatically to the ions and the absorption efficiency into the ions scales as I1/2. For example, absorption in a carbon target is only a few percent, but a large fraction of the absorbed energy is transferred to the ions