Propagation distance-resolved characteristics of copper plasma emission induced by axicon-focused femtosecond laser filamentation in air

Abstract

It is well known that Bessel beams have non-diffractive characteristics, which can be generated by Gaussian beams focused by an ideal axicon. In general, the length of filament generated by Bessel beams is longer than that by Gaussian beams and the electron density in the filament generated by Bessel beams is more uniform. This paper experimentally studied the propagation distance-resolved characteristics of copper plasma emission induced by axicon-focused femtosecond laser filamentation in the air. The evolution of the spectral intensity, plasma temperature, and electron density with the filament propagation path was obtained. The experiment results showed that when the base angle of the axicon was 5.0°, the spectral intensity along with the filament propagation path was more stable than that the base angle of the axicon was 0.5°. The changes in the plasma temperature and electron density along the filament propagation path were consistent with the change in the spectral intensity. This work provides a demonstration for the applications of filament-induced breakdown spectroscopy (FIBS), such as long-distance detection.