  We demonstrate a simple and high-performance laser-assisted technique for
silver nanoring fabrication, which includes the ablation of the Ag film by
focused nanosecond pulses and subsequent reactive ion polishing. The nanoring
diameter and thickness can be controlled by optimizing both the pulse energy
and the metal film thickness at laser ablation step, while the subsequent
reactive ion polishing provides the ability to fabricate the nanoring with
desirable height. Scattering patterns of s-polarized collimated laser beam
obliquely illuminating the nanoring demonstrate the focal spot inside the
nanoring shifted from its center at a distance of ~ 0.57Rring. Five-fold
enhancement of the photoluminescence signal from the Rhodamine 6G organic dye
near the Ag nanoring was demonstrated. This enhancement was attributed to the
increase of the electromagnetic field amplitude near the nanoring surface
arising from excitation of the multipole plasmon modes traveling along the
nanoring. This assumption was confirmed by dark-field back-scattering spectrum
of the nanoring measured under white-light illumination, as well as by
supporting finite-difference time-domain simulations.
