Bend loss in surface plasmon polariton band-gap structures

Using near-field optical microscopy, we investigate propagation of surface plasmon polaritons (SPPs) excited in the wavelength range of 720–830 nm at a corrugated gold-film surface with areas of 200-nm-wide and 45-nm-high scatterers arranged in a 410-nm-period triangular lattice containing line defects with double bends. We find that, for ∼2-μm-wide line defects and the wavelength of ∼740 nm, the double bend losses for bend angles of 15° and 30° are below 2 and 10 dB, respectively. Our data indicate that the bend loss increases approximately quadratically with the bend angle. We also demonstrate splitting and combining of two SPP line-defect modes in a 20-μm-long Y junction.