Mass Spectrometry of Organic Compounds Produced by Femtosecond Laser Ablation of Polymers

Femtosecond laser ablation is currently used to process various materials made of metal and ceramic. This technique has been applied to a polymer material to make narrow through-holes in electric circuit boards and to manufacture fine medical components as well. In this study, we focused the second harmonic emission (515 nm) of a femtosecond ytterbium (Yb) laser (120 kHz) onto the surfaces of several organic polymers under an ambient atmosphere and monitored the chemical species ablated from the surface by mass spectrometry using the fifth (206 nm) and fourth (257 nm) harmonic emissions of the Yb laser as the ionization source. As a result, highly unsaturated linear molecules such as polyenes/polyynes with many double and triple bonds were observed on the mass spectra measured for a linear saturated polymer such as polypropylene and also for aromatic polymers such as polyethylene terephthalate and polycarbonate. These results were in striking contrast to the data obtained using the second harmonic emission (532 nm) of a subnanosecond Nd:YAG laser for ablation, in which aromatic compounds were mainly observed even from a linear saturated polymer.