Laser Generated Magnetic Pulses: Hot Electron Propagation in Conducting and Dielectric Material

We report experimental evidence of electrostatic inhibition of fast electrons, generated in a highly resistive material upon irradiation with an intense ultra-short ($10^{16} W/cm^{2}$, $100 fmsec$) laser pulse. The experiment involves measurement of temporal evolution of self-generated magnetic pulses using pump-probe polarimetry. A comparison is made between the temporal behaviour of magnetic pulses generated with Aluminum and Glass targets. It is found that in contrast to Aluminium, self-generated magnetic pulse decays much faster in glass. This is attributed to the absence of return shielding currents in glass, which results in build up of electrostatic field, which in turn inhibits the movement of fast electrons. Fitting of experimental measurements using a one dimensional model, yields estimate of conductivity of Aluminium and glass, and penetration depth of hot electrons in these materials.