Novel applications for laser ablation of photopolymers

Abstract

The ablation characteristics of various polymers were studied at low and high fluences. The polymers can be divided into three groups, polymers containing triazene groups, polyesters with cinnamylidenemalonyl groups, and polyimide (PI) as reference polymer. The polymers containing the photochemically most active group (triazene) are also the polymers with the lowest threshold of ablation and the highest etch rates, followed by the designed polyesters and then PI. The triazene-polymer (TP) was studied at low fluences with additional techniques. UV–Vis spectroscopy and TOF-MS reveal that the triazene-chromophore decomposes also upon irradiation with fluences below the threshold of ablation. At the threshold fluence, a pronounced change is detected, i.e., an approximately 10 times higher decomposition rate. Nanosecond surface interferometry was applied to detect changes of the surface morphology of the TP and PI after irradiation with fluences above the threshold of ablation. In the case of the TP, no swelling of the surface is observed and etching starts and ends with the laser pulse, while a very pronounced swelling is detected for PI. The clear difference between PI and the designed polymers can be explained by a pronounced thermal part in the ablation mechanism of PI, while photochemical activities are more important for the TP. The combination of phase masks and the TP allows an efficient fabrication of three-dimensional topographies using laser ablation. The TP also reveals superior properties for applications in the near-IR. The carbon-doped polymer shows properties that are useful for the application of polymers in laser plasma thrusters for microsatellites.