Scanning near-field optical microscopy of fluorescent polystyrene spheres with a combined SNOM and AFM

We previously developed a scanning near-field optical microscopy (SNOM) by combining SNOM and atomic force microscopy (AFM), i.e. scanning near-field optic atomic-force microscopy (SNOAM). We demonstrated that this combination can be used for fluorescence imaging for a localized nanoarea. In the present work, the combined microscope was further improved by increasing the sensitivity with the aid of an objective lens, a pin hole, and a photon counting system. Performance of the modified combined AFM-SNOM was examined with a test sample which was prepared by spin coating of mixture of fluorescent and non-fluorescent polystyrene beads with polyvinyl alcohol (PVA) on a cover glass. The lateral resolution of the microscope was also examined by measuring a standing evanescent wave, which was formed by reflecting the incident laser beam on a prism.