Laser polymer ablation threshold lowered by nanometer hot spots

A polymer film doped with sensitizers was investigated after undergoing photothermal ablation when the sensitizers absorbed intense near-IR optical laser pulses. The sensitizers used, which efficiently converted optical energy into heat, comprised of near-IR absorbing molecules of the dye IR-165 and nanoparticles of graphite. This was undertaken to determine whether the larger diameter graphite hot spots could lower the ablation threshold. Results showed that the mechanism of ablation in dye-doped films was almost totally due to bulk thermal decomposition after the temperature became spatially uniform. In films doped with graphite nanoparticles, ablation at a significantly lower threshold was almost totally due to local thermal decomposition around the larger graphite hot spot.