A technique that allows direct optical imaging of nanostructures and determines quantitatively geometric nanofeatures beyond the classical diffraction limit by using high-refractive index glass microspheres is introduced. The glass microsphere is put on a nanostructure that is immersed in oil and collects the sample's near-field evanescent wave and transforms it into a propagating one, thereby generating a magnified image in the far-field which is recorded by a conventional oil-immersion microscope objective. Experimental results on nanostructures demonstrates a resolution of similar to lambda/4-lambda/7, where lambda is the illumination wavelength, by using a 60 mu m glass microsphere and a normal wideband halogen lamp as illumination source. A two-dimensional numerical study of the light propagation through a glass microsphere using finite element method (FEM) is performed, providing key insight into the microsphere's superior imaging capability. (C) 2015 Elsevier B.V. All rights reserved.
Demetri Psaltis, Carlo Gigli, Niyazi Ulas Dinç, Yang Li
Adrien Charles-François Raymond Descloux