Pulse Length Dependent Laser Ablation of Polymers

Abstract

Laser ablation of polyimide (PI) and polymethylmethacrylate (PMMA) at 248 nm with pulse lengths varied over six decades, from 200 fs to 250 ns, is presented. In order to obtain the desired pulse lengths in the femto- and picosecond range, the chirped 500 fs pulses of a hybrid dye-excimer laser system were modulated by a stretcher/compressor setup, mainly consisting of a pair of parallely mounted holographic reflection gratings with adjustable spacing, that introduces a defined group delay dispersion. Ablation was performed in vacuum with a mask projection setup.