# Helical transport in coupled resonator waveguides

## TL;DR

This paper demonstrates a novel design for coupled resonator waveguides that leverages pseudospin-momentum locking to significantly enhance disorder resistance, improving waveguide robustness and phase preservation.

## Contribution

It introduces a synthetic pseudospin-momentum coupling in CROWs, enabling disorder-resistant transport through pseudospin-momentum locking and bulk wave optimization, offering an alternative to topological edge states.

## Key findings

- Order of magnitude increase in Anderson localization length.
- Rapid saturation of wavepacket purity loss in disorder.
- Enhanced phase preservation before Anderson localization.

## Abstract

We show that a synthetic pseudospin-momentum coupling can be used to design quasi-one-dimensional disorder-resistant coupled resonator optical waveguides (CROW). In this structure, the propagating Bloch waves exhibit a pseudospin-momentum locking at specific momenta where backscattering is suppressed. We quantify this resistance to disorder using two methods. First, we calculate the Anderson localization length $\xi$, obtaining an order of magnitude enhancement compared to a conventional CROW for typical device parameters. Second, we study propagation in the time domain, finding that the loss of wavepacket purity in the presence of disorder rapidly saturates, indicating the preservation of phase information before the onset of Anderson localization. Our approach of directly optimizing the bulk Bloch waves is a promising alternative to disorder-robust transport based on higher dimensional topological edge states.