RF emissions from laser breakdown of target materials

The detection and analysis of the radio frequency (RF) waves emitted by the nanosecond laser breakdown of atmospheric air and metal (aluminum and copper) targets is presented. The emissions from different target materials were observed to be spectral selective with specific dependence on laser and antenna polarization. From the laser produced plasma (LPP) of atmospheric air, the RF output was found to be increasing with the input laser energy up to certain value, beyond which almost no emission was observed over the frequency range used in this study. This effect is attributed to the modification in the net induced dipole moment due to the multiple plasma sources in the LPP at higher input laser energies. Between the metals studied, RF emissions from copper were relatively higher than that of aluminum because of the better plasma conductivity of copper. Further studies may lead to an efficient technique for standoff material identification from the RF signature peaks.