Direct measurement of propagation losses in silver nanowires

We demonstrate a simple, direct measurement of propagation losses in single silver nanowires. Using a waveguiding nanoscale fiber taper for highly efficient launching, propagation surface plasmon polaritons are excited in the silver nanowire with high efficiency. The output intensity as light radiation at the end of the nanowire is quantified with high accuracy and repeatability. A typical propagation loss of 0.41 dB radicalmum (for 633 nm light) in a 260 nm diameter silver nanowire is obtained, which suggests that the propagation loss of a single silver nanowire could be lower than previously reported experimental results and should be much lower than those obtained by theoretical calculations.