Plasmonic diffractive patterns in metallic thin films by laser interference

ICSS & EMN Nanoparticles, Donostia-San Sebastián, Spain, May 9-12 2017. -- http://emnmeeting.org/Europe/icss/program/Collective oscillations of electrons in metal nanoparticles in presence of light produce a localized surface plasmon, thus optical response of the nanoparticles is characterized by an enhanced absorption at the plasmon resonance. Plasmonics of metal nanoparticles is an emerging field and the progress in the manipulation and synthesis of these objects in the last years allowed us to apply these optical properties in a great variety of applications from efficient light absorption in solar cells to DNA spectroscopy detection. Today, one of the major challenges is the effective production of surfaces with personalized visual color effects with direct applications in the development of personal identification systems. Laser irradiation of metallic thin films in percolated stage is an efficient and low cost method for the production of metal nanoparticles by fast melting/dewetting process in an easy, large area, single stage, efficient and low cost process. Laser interference is a versatile technique for the production of multidimensional patterned surfaces. When applied to metal films, the spatial modulated laser irradiation induces the periodic dewetting of the metal from the substrate resulting in the formation of nanoparticles at maxima of interference. These nanostructures in the case of Ag and/or Au are optically characterized by their plasmonic resonance in the visible range. Optical plasmonic response of metal nanoparticles depends on shape, composition and number density, and thus optical contrast (diffraction efficiency) between the regions transformed into nanoparticles and non-transformed regions at minima of interference can be tuned. Fig. 1 shows the SEM images of pattern produced by laser interference. In this work we report the production of bimetallic diffractive structures, with different [Ag]/[Au] ratio and different motives within periodicities in the range between 1.7 microns to 6.8 microns. We will present experimental data showing that these regions have different diffraction patterns according with the periodic motives and the plasmonic responses of the nanoparticles.Peer Reviewe