Effect of laser polarization on atomic and ionic emission in laser induced breakdown spectroscopy (LIBS).

Laser induced breakdown spectroscopy (LIBS) has become a proven contemporary workhorse for qualitative and quantitative analysis of materials. Recent developments in LIBS have been limited either to signal enhancement strategies or to advances in data analysis techniques that yield better interpretation of LIBS data. Explorations of the initial laser excitation stage of LIBS remain somewhat restricted. In particular, the influence, if any, of the polarization state of excitation laser remains unexplored to a large extent. The current work addresses this lacuna in knowledge by probing the influence of different polarization states of the excitation laser on LIBS spectra of metallic copper. Specifically, we investigate the behaviour of atomic and ionic emission lines with respect to change in polarization state of the incident laser light; our results show distinct polarization dependence. Our observations open up new opportunities of tackling the problem of relatively faint emissions from ionic species in the plasma by adjusting the polarization state of the laser. Our findings also highlight the urgent need for appropriate theoretical study to be undertaken so that proper insights can be developed into the physics that drive the observations that we report here.