  We demonstrate how optical nanofibers can be used to manipulate and probe
single-atom fluorescence. We show that fluorescence photons from a very small
number of atoms, average atom number of less than 0.1, around the nanofiber can
readily be observed through single-mode optical fiber under resonant laser
irradiation. We show also that optical nanofibers enable us to probe the van
der Waals interaction between atoms and surface with high precision by
observing the fluorescence excitation spectrum.
