Spatially and temporally resolved spectral emission of laser-induced plasmas confined by cylindrical cavities

Abstract

Laser-induced plasmas generated on pure copper samples in air with and without the presence of cylindrical cavities were investigated using spatially and temporally resolved spectroscopic measurements. The cylindrical cavities with variable diameters (3, 4 and 5 mm) and variable heights (1, 2, and 3 mm) were fabricated in quartz glass and placed on the sample surface and around the focused laser beam. Compared with plasmas generated without the cavity, the spectral emission intensities of plasmas generated with cylindrical cavities were enhanced after several microseconds, and the enhanced emission regions moved to higher locations above the sample with time. Plasma spatial and temporal emission was influenced by cavity diameter. As the diameter increased from 3 to 5 mm, the spectral emission was enhanced later in time and the enhancement became weaker. Plasma spatial and temporal emission was not significantly influenced by cavity height if the cavity was higher than the vapor plume. Shock wave theory was utilized to explain the observed phenomena.