Near-Field Optical Properties of Super-Resolution Near-Field Structures

Abstract

Super-resolution near-field structures, glass/SiN(170nm)/Sb(15nm) /SiN(20nm) and glass/ZnS-SiO₂ (20nm)/AgO_x (15nm)/ZnS-SiO₂ (20nm), have been studied by a tapping-mode tuning-fork near-field scanning optical microscope in transmission mode. Both propagating and evanescent field intensities were found at the focused spots of the surface of the super-resolution near-field structure. Images of the near-field intensity gradients at different excited laser powers showed that the area of the static evanescent intensity could be stably controlled. The enhancement of the near-field intensity, and the reduction of the focused spot through super-resolution near-field structure, glass/SiN(170nm)/Sb(15nm)/SiN(20nm) or glass/ZnS-SiO₂ (20nm)/AgO_x (15nm)/ZnS-SiO₂ (20 nm) have been directly observed in the near field. The near-field interactions of the 15 nm Sb and AgO_x Layers have been investigated, respectively, and the localized surface plasmons excited at the focused laser spot were shown to be the key sources of the strong enhancement in the near field.