Spatio-temporal characterization of ablative Cu plasma produced by femtosecond filaments.

We present the spatial and temporal characterization of the copper (Cu) plasma produced by the femtosecond laser filaments. The filaments of various lengths and intensities were generated with the aid of three different focusing lenses. Further, the filamentation induced breakdown spectroscopy (FIBS) measurements were carried out for each filament at three different positions along the length of the filament. The filaments were spatially characterized by estimating the plasma temperature and electron density. Our investigation has demonstrated that the centre of the filament is the best to obtain a maximum signal. Both the spectral line intensity and their persistence time are highest for the center of the filament. The enhanced persistence and the scalability of the spectral line intensity tested across different focusing geometries can boost the application of this technique in various fields.