SURFACE-PLASMON ENHANCED LASER-ABLATION OF THIN METAL-FILMS

Surface plasmon enhancement of laser ablation of thin Al films is exam ined with a view to its application in metal film patterning and nano- structuring. Al films, deposited on silica prisms, are first character ized by attenuated total reflection using a broadband UV source and ap propriate interference filter. The films are subsequently subjected to excimer laser radiation of wavelength 248 nm under conditions both of direct incidence from the air side of the film, and of surface plasmo n excitation in which light is incident through the prism at greater t han critical angle. For a given level of ablation damage in a particul ar film the fluence required using the surface plasmon technique is 3- 5 times less than that needed when direct incidence is used. This is r oughly in line with the energy absorbed in the film. From a practical standpoint it is clear that ablation of metal films can be achieved wi th much lower fluences than has hitherto been possible, thus reducing the requirements on laser output and relaxing the power handling const raints on any input optical elements.