Near-field optics: Direct observation of the field enhancement below an apertureless probe using a photosensitive polymer

We report the direct observation of the optical near-field enhancement at t he nanometric extremity of a metallic probe for apertureless scanning near- field optical microscopy. Our approach consists in making the "snapshot" of the spatial distribution of the optical intensity in the vicinity of the p robe end via a photosensitive polymer. This distribution is coded by polyme r surface topography which is characterized in situ by atomic force microsc opy using the same probe. Results clearly reveal nanometric dots correspond ing to local field enhancement below the tip end. The field enhancement is shown to be crucially dependent on the polarization state of the incident l aser beam as well as the tip material and geometry. The experimental result s are found to agree with the results of preliminary calculations. This exp eriment both constitutes a useful tool for investigating field enhancement below apertureless probes and has potential applications in nanophotolithog raphy. (C) 2001 American Institute of Physics.