Mode Properties of Flat-top Silver Nano-ridge Surface Plasmon Waveguides

TL;DR

This paper analyzes the electromagnetic properties of flat-top silver nano-ridge surface plasmon waveguides, revealing their mode characteristics, confinement behavior, and dispersion properties, which are crucial for nanoscale photonic applications.

Contribution

It provides detailed calculations of mode distributions, dispersion, and confinement, highlighting the quasi-TEM nature and size-dependent mode behavior of silver nano-ridge surface plasmons.

Findings

Nano-ridge modes are quasi-TEM with minimal longitudinal fields.

Mode confinement increases as ridge width decreases.

Mode approaches wedge plasmon modes with increasing ridge width.

Abstract

We investigate surface plasmon modes supported by flat-top silver nano-ridges. We calculate the mode electromagnetic field distribution, the dispersion curve, the travel range, and the figure-of-merit of the nano-ridge mode. We find that the nano-ridge surface plasmon modes are quasi-TEM modes with longitudinal field components three orders of magnitude smaller than the transverse field components. The quasi-TEM nature of mode profiles reveals that the propagation of free electron oscillations on the top of the nano-ridge contributes mainly to the tightly confined ridge mode. We also find that as the width of the nano-ridge decreases, the ridge mode becomes more tightly confined on the ridge top. As the width of the nano-ridge increases, the nano-ridge mode approaches two decoupled right-angle wedge plasmon modes.