A Waveguide Port Boundary Condition based on approximation space restriction for Finite Element Analysis

TL;DR

This paper introduces a novel waveguide port boundary condition for finite element analysis that simplifies implementation, reduces degrees of freedom, and enables efficient post-processing, demonstrated through numerical examples and a plasmonic sensor application.

Contribution

It proposes a new boundary condition based on approximation space restriction that enhances finite element analysis of waveguides by simplifying implementation and improving computational efficiency.

Findings

Reduces degrees of freedom at waveguide ports

Enables seamless post-processing of reflected power

Effectively applied to a nanograting plasmonic sensor

Abstract

A Waveguide Port Boundary Condition (WPBC) based on the restriction of the approximation space is presented in the context of Finite Element Analysis. As well as reducing the computational domain in the same manner as the traditional WPBC, the proposed scheme further reduces the degrees of freedom at the waveguide ports, simplifies the implementation and seamlessly provides post-processing results such as the reflected power in each waveguide mode. The boundary condition is thoroughly derived, and numerical examples are used as a support for the discussion on topics such as the needed number of modes to be employed at a waveguide port. Finally, a nanograting-based plasmonic sensor is analysed to illustrate further possibilities of the scheme.