Fundamental Study of Pulse Length Dependency for Laser Ablation and Melt Formation

Pennsylvania State Univ University Park, University Park PA

Investigators

Abstract

The research objective of this award focuses on the interaction between ultra-short laser pulses and materials and seeks to test the hypothesis that the target material?s electrons are accelerated into the material during ultra-short laser pulse irradiation resulting in an energy deposition thickness that is dependent on the laser pulse duration and energy. For an ultra-short laser pulse with large energy, it is postulated that this depth exceeds the optical absorption depth resulting in an observably thick melt layer and fast drilling rate that significantly exceed predictions of the current models. Further, if necessary, modifications to the electron acceleration mechanism may be proposed in order to achieve higher accuracy from numerical simulations. The numerical model will be verified by performing drilling with laser pulses ranging from 100 femptoseconds to 10 nanoseconds. The drilling depth and melt thickness will be measured and compared to results from simulations that use ponderomotive force as the electron acceleration mechanism. The drilling depths will be measured using surface profilometer methods and the melt thicknesses will be measured using electron backscatter diffraction and the transmission electron microscopy. The results of this research will benefit industrial laser applications and advance the science of laser-matter interaction. If successful, a theoretical model will provide accurate predictions of drilling depth and melt thickness across a broad range of interaction parameters extending from ultra-short pulse lasers to long-duration pulse and continuous wave lasers using fundamental principles of physics. In the long-term, the results of this research will benefit areas of laser system manufacturing, industrial laser applications, and contribute to education on electromagnetic wave interaction with matter.