Sagnac interference in integrated photonics for reflection mirrors, gyroscopes, filters, and wavelength interleavers

TL;DR

This paper reviews the development and implementation of integrated Sagnac interferometers in photonics, highlighting their advantages, recent device realizations, and applications in reflection, gyroscopes, filters, and wavelength interleavers.

Contribution

It provides a comprehensive overview of integrated Sagnac interferometers, comparing them with other photonic devices and presenting recent experimental results.

Findings

Successful realization of Sagnac devices in integrated photonics

Enhanced stability and reduced footprint compared to traditional methods

Demonstrated applications in gyroscopes, filters, and wavelength interleavers

Abstract

As a fundamental optical approach to interferometry, Sagnac interference has been widely used for reflection manipulation, precision measurements, and spectral engineering in optical systems. Compared to other interferometry configurations, it offers attractive advantages by yielding a reduced system complexity without the need for phase control between different pathways, thus offering a high degree of stability against external disturbance and a low wavelength dependence. The advance of integration fabrication techniques has enabled chip-scale Sagnac interferometers with greatly reduced footprint and improved scalability compared to more conventional approaches implemented by spatial light or optical fiber devices. This facilitates a variety of integrated photonic devices with bidirectional light propagation, showing new features and capabilities compared to unidirectional-light-propagation devices such as Mach-Zehnder interferometers (MZIs) and ring resonators (RRs). Here, we present our latest results for functional integrated photonic devices based on Sagnac interference. We outline the theory of integrated Sagnac interference devices with comparisons to other integrated photonic building blocks such as MZIs, RRs, photonic crystal cavities, and Bragg gratings. We present our latest results for Sagnac interference devices realized in integrated photonic chips, including reflection mirrors, optical gyroscopes, basic filters, wavelength (de)interleavers, and optical analogues of quantum physics.