Mid-Infrared Resonant Ablation of PMMA

Laser ablation proved to be a reliable micro-fabrication technique for patterning and structuring of both thin film and bulk polymer materials. In most of the industrial applications ultra-violet (UV) laser sources are employed, however they have limitations such as maintenance costs and practical issues. As an alternative and promising approach, mid-infrared resonant laser ablation (RIA) has been introduced, in which the laser wavelength is tuned to one of the molecular vibrational transitions of the polymer to be ablated. Consequently, the technique is selective in respect of processing a diversity of polymers which usually have different infrared absorption bands. In this paper, we present mid-infrared resonant ablation of PolyMethyl MethAcrylate (PMMA), employing nanosecond laser pulses tunable between 3 and 4 microns. This RIA nanosecond laser set-up is based on a commercial laser at 1064 nm pumping a singly resonant Optical Parametric Oscillator (OPO) built around a Periodically-Poled Lithium Niobate (PPLN) crystal with several Quasi-Phase Matching (QPM) periods. RIA has been successfully demonstrated for structuring bulk PMMA, and selective patterning of PMMA thin films on a glass substrate has been implemented.