Temporal and Spectral Characterization of Electromagnetic Pulse Emitted From Nanosecond Pulsed Laser Produced Aluminum Plasma

Abstract

The electromagnetic pulse (EMP) emitted from the plasma produced by interaction of 5-ns pulsed Nd:YAG ( $\lambda =532$ nm) laser with the aluminum target was measured. The laser irradiance at the target was varied in the range of $3.12\times 10^{9} - 4.56\times 10^{10}$ W/cm2 and its influence on the temporal and spectral parameters of the EMP was investigated. The EMP starts well after the termination of laser pulse and the duration of EMP is up to several hundred nanoseconds. The EMP start time was found to decrease from approximately 150 to 60 ns with the rise of laser irradiance. The rise time of EMP (~50 ns) does not seem to vary with the laser irradiance. The signal consists of several resonance peaks in the frequency bin of 20–200 MHz, whose intensity also depends on the laser irradiance. The observed dependence of EMP intensity on the laser irradiance and frequency of fundamental-mode emission is compared with the theoretical predictions. The considerable delayed emission of EMP indicates that its origin can be related to the macroscopic charge separation phenomena during the plasma expansion.