Deep-UV microsphere-assisted ultramicroscopy

Microsphere-assisted ultramicroscopy is a powerful, yet simple, technique to visualize nanometric-scale objects with visible light. In this method, dielectric microspheres are placed in contact with the nanoscale objects, so that the spheres experience object´s optical near-fields. The mechanism of imaging is still debated in the literature; however it is likely to involve surface plasmon resonances in metallic nanostructured objects, whispering gallery modes in dielectric microspheres and other factors. In this work we extended this technique from visible to deep-UV range. It is shown that imaging of nanoplasmonic structures at the wavelength of 248 nm can be achieved with ~ 55 - 60 nm resolution, far beyond the diffraction limit. These results could shed light on the mechanism of super-resolution imaging by microspheres and further advance this technology for practical applications.