Surface scattering and band gaps in rough waveguides and nanowires

TL;DR

This paper investigates how boundary roughness in waveguides and nanowires affects their transmission and band gaps, using microwave experiments and a novel surface scattering theory that accounts for the surface gradient.

Contribution

It introduces a new scattering mechanism based on the squared gradient of surface profiles and validates the theory with experimental and numerical results.

Findings

Surface roughness significantly influences transmission properties.

The squared gradient scattering mechanism accurately predicts experimental results.

Boundary profile design can control transmission and band-gap properties.

Abstract

The boundaries of waveguides and nanowires have drastic influence on their coherent scattering properties. Designing the boundary profile is thus a promising approach for transmission and band-gap engineering with many applications. By performing an experimental study of microwave transmission through rough waveguides we demonstrate that a recently proposed surface scattering theory can be employed to predict the measured transmission properties from the boundary profiles and vice versa. A new key ingredient of this theory is a scattering mechanism which depends on the squared gradient of the surface profiles. We demonstrate the non-trivial effects of this scattering mechanism by detailed mode-resolved microwave measurements and numerical simulations.