Pyroelectric detection of ultraviolet laser ablation products from polymers

Abstract

A simple pyroelectric detector has been constructed and used to measure the ablation velocity for various polymers as a function of laser (248 nm) fluence. The advantage of this approach over other techniques is that a full sampling of the products in the ablation plume is obtained. Results for polymethyl methacrylate (PMMA) ablation can be interpreted in terms of a single explosive decomposition process in which numerous small fragments such as C2, CO, and CO2 propel small segments of the polymer at velocities which are scaled to the square root of their molecular weights. Data for polymide suggest that this polymer is decomposed by laser photons principally into small molecules. The solid carbon that is obtained on ablation in air is probably derived by reactions between carbon clusters. This technique is suitable for the study of the angular distribution of the ejected material which is useful for modeling and in schemes for the deposition of material by laser ablation.