$\hbox{Au/SiO}_{2}$ Nanoring Plasmon Waveguides at Optical Communication Band

Abstract

We design and investigate plasmon waveguides based on linear arrays of Au nanorings in an SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> = 3 dB/655 nm and gamma <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> = 3 dB/443 nm and group velocities nu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gT</sub> = 0.177c <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and nu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gL</sub> = 0.327c <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> for transverse and longitudinal polarizations, respectively, where c <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the speed of light in a vacuum.