Comparison of the ablation behavior of polymer films in the IR and UV with nanosecond and picosecond pulses

Experiments are performed to compare the ablation behavior in the IR and UV spectral regions of a doped standard polymer, PMMA, and a specially tailored photopolymer, i.e., a triazene copolyester, to elucidate the underlying mechanisms. The results are discussed in light of current theories about photochemical and photothermal pathways of ablation. Further experiments are performed with nanosecond and picosecond pulses to study the impact of pulse length on the material. From the failure to induce ablation in the IR by doping the specialty polymer with an optical molecular heater we conclude that etching in the UV of this compound is mainly governed by a photochemical process. This result is contrasted by successful ablation of doped PMMA in the IR via a thermal unzipping mechanism. With respect to practical applications, the results show convincingly that the presence of an absorbing chromophore in the polymer is a prerequisite for achieving high-resolution structuring, since molecular absorption is required for an efficient distribution of incorporated photonic energy.