Transient reflectivity behavior of pure aluminum at 10.6 μm

Abstract

Time-resolved measurements of specular reflectivity of polished pure aluminum surfaces subjected to intense 10.6-μm pulsed-laser radiation in vacuum are reported. A sharp decrease in reflectivity to an anomalously low value (35%) was observed midway in the pulse followed by nearly complete recovery of full reflectivity near the end of the pulse. The peak-power-density threshold for this phenomenon was found to agree with the intrinsic surface melt threshold as determined from numerical heat-transfer calculations and microscopic examination of the samples.