Coupling of optical far fields into apertureless plasmonic nanofiber tips

This paper reports on the excitation of surface plasmons on gold-coated nanofiber tips by side illumination with a laser beam and the coupling of the surface plasmons to the optical fiber. The measurements show a strong dependence of the coupling efficiency on the incidence angle with a maximum coupling efficiency on the order of a few percent. Moreover, the fiber tip was used as a scanning probe device for measuring the beam waist of a focused laser beam. This work is motivated by the goal to use such plasmonic nanofiber tips in quantum optics experiments with cold atoms.