Abstract

In an underdense plasma formed by an ultrashort pulse the initial density and magnetic field are determined by above threshold ionization. In the absence of internal plasma fields the average electron energy is a function of the laser wavelength and polarization of the light while the magnetic field results from the current imposed in the plasma when many circularly polarized photons are absorbed. In this manner, otherwise inaccessible plasma conditions can be obtained. A simple model of above threshold ionization is used to obtain quantitative predictions. We will also describe experiments confirming the model.

© 1989 Optical Society of America