Delocalized Photomechanical Effects of UV ns Laser Ablation on Polymer Substrates Captured by Optical Holography Workstation: An Overview on Experimental Result

Abstract

A brief overview of results from an experimental investigation performed on polymer materials to examine delocalized photomechanical effects generated due to UV laser ablation is provided. Delocalized structural modifications were observed in PMMA, PS by means of optical holographic interferometry. The integrity of samples was examined before and after irradiation in 193 and 248 nm (15 ns) above and below ablation threshold, F = 0.1–1.0 J/cm2. A value of structural continuity was initially determined for each sample by generation of a reference holographic image before irradiation. Microscopic discontinuities were intentionally induced to act as preexistent defects. Sequential holographic recording monitored the growth of morphological alterations according to the number of pulses in the neighbor as well as far from the preexistent discontinuities. The imposed alterations are visually observable at the whole extent of the irradiated sample in distances far off the ablation spot as local cracks and voids. The induced flaws cannot be classified as transient or instantly generated. Fracture follows a long-term emergence and deterioration pattern. Extensively fluctuated long-term effects were also observed in laser-assisted varnish removal of multilayered technical samples simulating Byzantine icons with decrease of effect duration and fluctuation being according to increase in sample homogeneity.