Nonlocal response in thin-film waveguides: loss versus nonlocality and breaking of complementarity

TL;DR

This paper explores how nonlocal electron response influences surface-plasmon polariton guiding in various thin-film waveguides, revealing effects on dispersion, loss, and fundamental symmetries.

Contribution

It introduces a hydrodynamic model to analyze nonlocal effects on waveguide dispersion and demonstrates the breaking of waveguide complementarity due to nonlocality.

Findings

Nonlocal effects modify dispersion relations of waveguides.

Nonlocality can increase or decrease propagation losses.

It breaks the complementarity between MIM and IMI waveguides.

Abstract

We investigate the effects of nonlocal response on the surface-plasmon polariton guiding properties of the metal-insulator (MI), metal-insulator-metal (MIM), and insulator-metal-insulator (IMI) waveguides. The nonlocal effects are described by a linearized hydrodynamic model, which includes the Thomas-Fermi internal kinetic energy of the free electrons in the metal. We derive the nonlocal dispersion relations of the three waveguide structures taking into account also retardation and interband effects, and examine the delicate interplay between nonlocal response and absorption losses in the metal. We also show that nonlocality breaks the complementarity of the MIM and IMI waveguides found in the non-retarded limit.