Anomalous absorption of high intensity subpicosecond laser pulses

Abstract

When very intense laser radiation is incident on a sharply bounded overdense plasma, strong energy absorption can be accounted for by the electrons that are drawn into the vacuum and sent back into the plasma with velocities on the order of the quiver velocity. The absorption process takes place on the time scale of the laser light cycle and no corona or underdense plasma need be present. The validity of this mechanism is confirmed through 2 1/2 ‐dimensional particle‐in‐cell (PIC) simulations in the case of a two‐pump system. From these simulations the presence of strong average magnetic fields is also noted, even without the presence of a thermal gradient, because of the average current of electrons drawn from the overdense plasma.