Field-enhanced scanning near-field optical microscopy

This manuscript reviews the principles and recent advances of scanning near-field optical microscopy based on tip-induced field enhancement. These scanning microscopes utilize minute probes to locally enhance an electromagnetic field through a complex interplay between surface plasmon excitation and localization of electric charges by geometrical singularities. The necessary conditions leading to an electromagnetic enhancement will be reviewed, as well as the means to characterize it. A brief account of the theoretical framework will be given, together with applications of the technique ranging from chemical imaging to nanolithography.