Label-Free Super-Resolution Imaging of Transparent Dielectric Objects Assembled on Silver Film by a Microsphere-Assisted Microscope

摘要： In optical microscopy, label-free imaging transparent dielectric objects with sub-wavelength features is still a challenge. We propose a method to super-resolution image a label-free transparent periodic object using the microsphere-assisted bright-field microscope. A two-dimensional array of label-free hexagonally close-packed polystyrene (PS) nanoparticles with a diameter of 250 nm assembled on a silver film coated glass slide can be discerned by coupling a classical optical microscope with a 30-μm-diameter BaTiO3 glass (BTG) microsphere. However, when the PS nanoparticle array with the same diameter is assembled on either a glass slide or a high-reflectance dielectric multilayer coated glass slide, it cannot be resolved. We propose that period plasmonic near-field illumination is generated due to the excitation of surface plasmon polarition modes on periodically structured interfaces. More high-frequency information of the object is coupled into the BTG microsphere lens, resulting in the improvement of imaging resolution.