Observation of the resonantly enhanced resolution of imaging of fluorescent nanospheres due to their coupling to the metallic nanoplasmonic arrays

Virtual imaging through dielectric microspheres is shown to possess the resolution beyond the classical diffraction limit, but the factors responsible for such resolution are debated in the literature. In this work, we experimentally demonstrated an important role of spectral overlap between the emission band of a fluorescent (FL) object and the spectral peak of localized surface plasmon resonance (LSPR) in the underlying metallic periodic nanostructure. As an object, we used green and blue FL nanospheres placed at the top of Au and Al arrays with different periods. It is shown that the maximal resolution beyond the diffraction limit can be achieved in confocal microscopy of green (blue) FL nanospheres at the top of Au(Al) arrays. Our results provide the first direct evidence for the critically important role of resonant coupling of emission of point-like objects to LSPRs in the underlying nanostructure for achieving the super-resolution.