Thermal coupling of pulsed 0.53-pm laser radiation to aluminums in air

Abstract

Experiment and theoretical analysis have been performed to investigate the ther- mal coupling of focused pulsed 0.53-pm laser radiation to aluminum targets irradiat- ed in air. A normal pulsed energy of 0.1J and pulsed duration of lOns (FWHM) are used. The thickness of the experimental aluminum slabs is - 0.5mm. Thermal coupling coefficients are measured for commercial aluminums (as-received, polished, frosted surface). We find low intensity (.S108w/cm2) thermal coupling coefficients of 0.2 for as-received, 0.15 for polished and 0.25 for frosted-surface aluminums. Thermal coupling coefficients of larger than 0.4 were observed with the onset of a surface plasma. After the surface plasma formation, the thermal coupling coefficients fall down with the increasing intensity. Measurements are also presented for the plasma formation threshold above aluminum target irradiated at 0.53-pm. An intensity threshold of 2 X108w/cm2 is indicated for a 10 us laser pulse (FWHM).