Spiral surface plasmon modes inside metallic nanoholes

Abstract

Spiral surface plasmon (SSP) modes that propagate inside a silver (Ag) nanohole are investigated by performing both simulations and theoretical analyses. The SSP modes are formed by a linear combination of two rotating SP eigenmodes of the Ag nanohole in the fast-wave branch. Inside a uniform Ag nanohole, the handedness and the number of strands of the SSP modes are determined by both the component SP eigenmodes and their rotation directions. The spiral pitch of the SSP mode increases with the nanohole radius for a fixed wavelength and is inversely related to the incident wavelength for a fixed nanohole radius. Inside a tapered Ag nanohole, the spiral pitch decreases with the reduction of nanohole radius. However, the azimuth-integrated field energy density increases to a maximum value and then falls. For a tapered Ag-clad fiber capped by a tapered Ag nanorod, the SSP mode reverses its handedness when it passes through the fiber-nanorod interface. Furthermore, using this composite structure, the field energy density of SSP mode that arrives at the tip of the tapered nanorod is largely increased.

Conversion of a Helical Surface Plasmon Polariton into a Spiral Surface Plasmon Polariton at the Outlet of a Metallic Nanohole

“…The size-dependent color filter of a two-dimensional (2D) nanohole array in a metal film for light transmission was discovered by Ebbesen’s experiments. − In the past decades, the related issues have been extensively studied. − The phenomena are found to be related to a surface plasmon polariton (SPP) propagating along nanoholes in a metal film. − On the one hand, Shin et al found that the HE 11 mode is the dominant propagating mode in a nanohole of a thick Ag film . On the other hand, the SPP at the interface of a metal film induced by a transmission light via a metallic nanohole has been studied. − For example, Yin et al used near-field scanning optical microscopy (NSOM) to measure an SPP originating from a nanohole at the upper interface of Au film irradiated by a linearly polarized (LP) light at the lower side .…”

A transversely localized light in a waveguide: the analytical solution and its potential application

“…(see [28] and references there). The developed nanooptics increases an interest to the theory of a light in the planar waveguides characterized by various geometry and material properties [24,26,[29][30][31][32][33][34][35][36]. Now the researchers need to use the numerical methods providing only numerical data of the calculations restricted by the concrete physical and geometrical parameters of the planar waveguides.…”

“…The existing theoretical approaches permit only the approximate solutions of the transcendental equation in three limiting cases: i) near cuttoff, ii) at short-wave limit Lω/c ≫ 1, and iii) in the strongly asymmetrical case (see, for example [22]). While the nanowaveguide structures characterized by the intermediate sizes (Lω/c ≤ 1) are studied only by the numerical methods [22,43] (see also recent works [24][25][26][27][29][30][31][32][33][34][35][36]).…”

“…metal insulator metal waveguide with bends [24], as a part of split-ring resonators [25], as a subwavelength hole in a thick screen [26], or as an approximation model for V-groove waveguides [27]), waveguide arrays, etc (see [28] and references there). The developed nano-optics increases interest in the theory of a light in the planar waveguides characterized by various geometry and material properties [24,26,[29][30][31][32][33][34][35][36]. Now, researchers need to use numerical methods for the study of light propagation in such waveguides.…”

“…The existing theoretical approaches permit only the approximate solutions of the transcendental equation in three limiting cases: (i) near cuttoff (ck z n ω ), (ii) at short-wave limit L c 1 / ω (ck z n ω ), (iii) in the strongly asymmetrical case (see, for example, [22]). While for the nanowaveguide structures with the practically used sizes (ck z n ω ∼ ), the equation ( 2) is now studied only numerically [22,43] (see also recent works [24][25][26][27][29][30][31][32][33][34][35][36]). Therefore, in this work we develop another theoretical approach.…”