# Towards Topological Protection based millimetre wave devices

## TL;DR

This paper demonstrates a modal launcher and a topological contra-directional coupler for millimetre wave devices, enabling better interaction of topological modes with trivial modes in microwave range.

## Contribution

It introduces a modal launcher for topological metawaveguides and demonstrates a topological contra-directional coupler, advancing topological protection in millimetre wave devices.

## Key findings

- Negligible reflection interface between topological and conventional waveguides
- Successful demonstration of a topological contra-directional coupler
- Enhanced interaction of topological modes with trivial modes

## Abstract

Feasibility of Topological Metawaveguides supporting helical propagation in the microwave range has been recently proven. The advantages of unidirectional propagation supported by such waveguides however can only be exploited in real devices if topological modes are endowed with the capability to interact within themselves as well as with trivial modes. Here we show a modal launcher to interface a topological metawaveguide with conventional circular waveguides with negligible reflection and we exploit the properties of coupled topological modes to show a proof of concept of a topological contra-directional coupler.