Effect of laser polarization on atomic and ionic emissions in Laser-Induced Breakdown Spectroscopy (LIBS)

Laser-Induced Breakdown Spectroscopy (LIBS) is attracting a great deal of interest in qualitative and quantitative analysis of materials. Close observation reveals that developments in the science that underpins LIBS as an analytical technique are limited to either signal enhancement strategies or newer data analysis techniques that facilitate better interpretation of raw LIBS data. Developments related to the excitation part of LIBS have been restricted to the effects of laser beam characteristics or the effect of ambient experimental conditions. The influence, if any, of the polarization state of the excitation laser has largely remained unexplored. We address this lacuna by probing the influence of different polarization states of the excitation laser on LIBS spectra of metals (copper and silver) and non-metals (polyethylene) by analyzing the polarization-dependent behavior of both atomic and ionic emission lines. Our observations open the possibility of tackling the problem of relatively faint emissions from ionic species in the plasma by appropriately manipulating the polarization state of the incident laser beam; this may lead to easy-to-implement improvement in the performance of LIBS instruments. Graphical abstract