Tapered optical fibers are promising one-dimensional
nanophotonic waveguides that can provide efficient coupling between their
fundamental mode and quantum nanoemitters placed inside them. Here,
we present numerical studies on the coupling of single nitrogen-vacancy
(NV) centers (single point dipoles) in nanodiamonds with tapered fibers.
Our results lead to two important conclusions: (1) A maximum coupling
efficiency of 53.4% can be realized for the two fiber ends when the NV
bare dipole is located at the center of the tapered fiber. (2) NV centers
even in 100-nm-sized nanodiamonds where bulk-like optical properties
were reported show a coupling efficiency of 22% at the taper surface,
with the coupling efficiency monotonically decreasing as the nanodiamond
size increases. These results will be helpful in guiding the development
of hybrid quantum devices for applications in quantum information science.