Optical near-field enhancement around lithographic metallic nanostructures using an azo-dye polymer: direct observation and realization of sub-wavelength complex structures

Abstract : We report on the direct observation of optical near-field enhancement around metallic nanoparticles. We used an easy to set up approach which consists in irradiating a photosensitive azo-dye polymer film spin-coated on metallic nanostructures. Photoinduced topographical modifications of the polymer film surface are characterized after irradiation by atomic force microscopy (AFM). Comparisons between AFM images and numerical simulations show that these photo-induced topography agrees with the near-field intensity distribution around the nanostructures. The possibility of generating complex structures is demonstrated.