# Brillouin-based phase shifter in a silicon waveguide

## TL;DR

This paper demonstrates a broadband 360-degree phase shifter in silicon waveguides using Brillouin scattering and RF interference, enabling practical applications in beam forming and microwave photonics.

## Contribution

The authors present a novel phase enhancement technique that achieves a full 360-degree phase shift in silicon waveguides, overcoming previous gain limitations.

## Key findings

- Achieved a 360-degree phase shift over 15 GHz bandwidth.
- Implemented a phase enhancement factor of 25.
- Enabled practical broadband Brillouin phase shifter for applications.

## Abstract

Integrated silicon microwave photonics offers great potential in microwave phase shifter elements, and promises compact and scalable multi-element chips that are free from electromagnetic interference. Stimulated Brillouin scattering, which was recently demonstrated in silicon, is a particularly powerful approach to induce a phase shift due to its inherent flexibility, offering an optically controllable and selective phase shift. However, to date, only moderate amounts of Brillouin gain has been achieved and theoretically this would restrict the phase shift to a few tens of degrees, significantly less than the required 360 degrees. Here, we overcome this limitation with a phase enhancement method using RF interference, showing a 360 degrees broadband phase shifter based on Brillouin scattering in a suspended silicon waveguide. We achieve a full 360 degrees phase-shift over a bandwidth of 15 GHz using a phase enhancement factor of 25, thereby enabling practical broadband Brillouin phase shifter for beam forming and other applications.