Giant near-field optical enhancement with subnanometer tip-sample distance sensitivity

Summary form only given. In a recent paper, A.V. Bragas et al. (1998) have shown a giant optical field enhancement (more than 1000) at the tip-sample junction of a scanning tunneling microscope. The magnitude of the field enhancement obtained is larger than expected from abundant calculation performed for different tip-sample geometries. In this work it is shown that when the metallic tip is approached to a sample to subnanometer distances, and it is shone with light, the field enhancement at the tip is increased by a resonant mechanism, yielding light scattering signals extremely sensitive to the tip-sample distance. Experimental results indicate subnanometer sensitivity, and a model is given consistent with the results.