A Fundamental Limit on Propagation Loss of Waveguides with Subwavelength Mode Size

TL;DR

This paper establishes a fundamental limit on the trade-off between mode confinement and propagation length in waveguides, extending the diffraction limit concept and providing a benchmark for plasmonic material performance.

Contribution

It introduces a generalized trade-off relation for waveguide modes and a material loss merit factor to optimize plasmonic waveguide design.

Findings

Lower bound on propagation loss for subwavelength waveguides

Generalized diffraction limit for guided modes

Material loss merit factor for comparing plasmonic materials

Abstract

A fundamental trade-off relation between the cross sectional confinement and propagation length of an arbitrary mode of a general waveguide is presented. This limit is a generalization of the well-known diffraction limit for guided modes. The results provide a lower bound on propagation loss of plasmonic waveguides which are attractive for their deep subwavelength mode dimensions. We also introduce a material loss merit factor that sets a criterion for comparing different plasmonic materials for achieving the best trade-off between confinement and loss.