Au/SiO2 Nanoring Plasmon Waveguides at Optical Communication Band

We design and investigate plasmon waveguides based on linear arrays of Au nanorings in an SiO₂ host for use in an optical communication band (lambda ~ 1550 nm). Nanoring particles have better tunability and can achieve more laterally compact waveguides, compared to their solid counterparts, such as nanospheres and nanodisks. Three-dimensional simulations employing the finite-difference time-domain algorithm are used to determine the set of geometrical parameters attaining localized surface plasmon resonance at 1550 nm. It is found out that, in the SiO₂ host, Au nanorings attain LSPR at 1550 nm with a 175-nm inner diameter, a 35-nm height, and a 30-nm thickness. It is shown that linear chains of Au nanorings can transport the electromagnetic energy at 1550 nm, with transmission losses gamma_T = 3 dB/655 nm and gamma_L = 3 dB/443 nm and group velocities nu_gT = 0.177c₀ and nu_gL = 0.327c₀ for transverse and longitudinal polarizations, respectively, where c₀ is the speed of light in a vacuum.