Three-dimensional photography and reconstruction of jets and droplets ejected from the surface of excimer laser ablated molten polyethylene-glycol 1000

Abstract

Solid debris, namely particles, produced during pulsed laser deposition procedures significantly reduces the quality and homogeneity of the deposited thin layers. Using a liquid target the occurrence of the solid debris was completely avoided; however, molten droplets were observable on the thin-film surfaces resulting in quality deterioration in this case, too. Several methods have already been suggested to eliminate these but the efficiency of these procedures is not excellent, because the droplet ejection processes are not completely described yet. Molten polyethylene-glycol (PEG) 1000 (Tm=70 °C) was ablated by an ArF excimer laser and a time-resolved investigation of jet and droplet developments was performed using a fast photographic arrangement. The applied fluence range was 0.8–8.8 J/cm2. For a three-dimensional reconstruction the exposing dye laser beam was divided into three parts and directed onto the irradiated part of the surface of the PEG sample from three different directions. Three video cameras facing the exposing light took concurrent shots of the process. Transmissive pictures of the ablated material were taken within a 50–1500 μs range of delay. The three-dimensional reconstruction of the ejected jets and droplets was performed based on the recorded three concurrent photographs. Results were in co-relation with ejections seen in the original snapshots and accurately dimensioned to the object appearing on them.