Laser‐beam deflection measurements and modeling of pulsed laser ablation rate and near‐surface plume densities in vacuum

摘要

Quantitative measurements of ablated material from the surface of polyethyleneterephthalate (PET) by 248‐nm excimer laser fluences up to 10 J/cm2 are performed by HeNe laser‐beam deflection in vacuum and by photoacoustic depth profiling in air. HeNe laser‐beam deflection measures the density of gas phase material present in the ablation plume. Photoacoustic depth profiling is a nonintrusive diagnostic that directly measures the etch depths from laser ablation. A hydrodynamic model consisting of a centered rarefaction wave that reflects off the PET surface is shown to describe the laser deflection signals. From these measurements an estimate of the initial temperature of the ablated species is found.