Apertureless near-field optical microscopy

The physical principles of apertureless scanning near-field optical microscopy (SNOM) are analyzed. The related measurement methods for the obtainment of best resolution performance and artefact suppression are discussed. Exploiting SERS and MEF effects, locally induced by the tip, a-SNOM allows for nanometer scale chemical discrimination based on fluorescence and Raman scattering with unprecedented high sensitivity. The possibility to access the non-linearity regime at the nanoscale, is direct consequence of the development of a-SNOM techniques, which has direct implications both in two-photons photoluminescence (PL) imaging and in near-field optical lithography (NFOL).