%0 Journal Article
%T Delocalized Photomechanical Effects of UV ns Laser Ablation on Polymer Substrates Captured by Optical Holography Workstation: An Overview on Experimental Result
%A Vivi Tornari
%J Advances in Optics
%D 2014
%R 10.1155/2014/105482
%X 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¨C1.0£¿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. 1. Introduction Irradiation of solid organic material with pulsed ultraviolet laser light of intense power density leads to cold etching or ablative photodecomposition (APD) of the substrate. The APD effect located in the limited region of the laser spot is attributed to local photochemical mechanism causing discrete ejection of target material without altering the adjacent bulk which allows for controlled substrate processing conveniently suited for many applications. The mass ejection and the expansion of high-density plasma though induce a mechanical effect characterized by a recoil pressure and a shock wave propagating inside the solid. The photomechanical effects in contrast to the presented study are mainly reported in literature in concern to the physical processes in the ablated region as influence of pressure versus time. Specifically, laser ablation using 193, 248£¿nm excimer laser radiation is commonly used [1¨C12] in microelectronic industry for etching of polymer substrates and in medical applications for controlled excision of tissue as well as in ophthalmology and in photorefractive surgery for restoring of myopia and has been proved to be a highly
%U http://www.hindawi.com/journals/ao/2014/105482/