Propagation losses in gold nanowires

We report direct measurement of propagation losses in single gold nanowires around visible and near-infrared bands. By directly measuring the propagation-distance-dependent output of the nanowire via fiber-taper-assistant near-field-coupling technique, we obtain a typical loss of 0.89 dB/µm at 785-nm wavelength in a 210-nm-diameter gold nanowire. We have also investigated the dependences of propagation losses on the nanowire diameter and light wavelength, and shown that the propagation loss is averagely increased with decreasing diameter and wavelength. Our results from direct measurements offer an unambiguous loss information of gold nanowires, as well as a helpful reference for gold-nanowire-based plasmonic circuits and devices.