Rapid super-resolution imaging of sub-surface nanostructures beyond diffraction limit by high refractive index microsphere optical nanoscopy

Sub-surface nanostructures cannot be observed by scanning electronic microscopy or standard scanning probe microscopy. They are also outside the resolution limit of standard optical microscopes. In this paper, we demonstrate super-resolution imaging of sub-surface nanostructures beyond the optical diffraction limit. Sub-surface Blu-ray recorded data structures (100–200 nm) have been observed directly with submerged microsphere optical nanoscopy (SMON) using TiO2–BaO–ZnO glass microspheres (refractive index=2.2) of 60 µm diameter immersed in water coupled with a standard optical microscope. Theoretical analysis of the imaging phenomena was carried out by the characteristics of electrical field Poynting vectors and photonic nanojets.