Photochemically assisted laser ablation of doped polymethyl-methacrylate

Abstract

Polymethyl-methacrylate doped with organic dye molecules can be photoablated with 308 or 351 nm nanosecond excimer laser pulses. For comparison, pure polymethyl-methacrylate cannot be photoablated at these wavelengths. The definition of the ablation pattern is comparable to the results achieved by the use of 248 nm pulses on pure polymethyl-methacrylate. Etch rates of about 50 μm per pulse can be reached, which is ten times the maximum etch rate of 248 nm pulses. An example of an effective dopant molecule is 1,3-diphenyltriazene. The ablation process is governed by gas production due to laser-induced photodissociation of the dopant. The ablation rate increases with growing laser fluence up to a saturation level, which is approximately proportional to the reciprocal dopant concentration (0.2 to 2 wt%).