Waveguide integrated high performance magneto-optical isolators and circulators on silicon nitride platforms

TL;DR

This paper demonstrates high-performance magneto-optical isolators and circulators integrated monolithically on silicon nitride platforms, achieving record Faraday rotation, high isolation, and low insertion loss, suitable for photonic integrated circuits.

Contribution

It introduces the first monolithic integration of MO isolators on SiN with record performance, using standard foundry processes and high-quality MO garnet films.

Findings

Record high Faraday rotation of -5900 deg/cm on SiN

Achieved 28 dB isolation ratio at 1570.2 nm

Low insertion loss of 1 dB and temperature stability

Abstract

Optical isolators and circulators are indispensable for photonic integrated circuits (PICs). Despite of significant progress in silicon-on-insulator (SOI) platforms, integrated optical isolators and circulators have been rarely reported on silicon nitride (SiN) platforms. In this paper, we report monolithic integration of magneto-optical (MO) isolators on SiN platforms with record high performances based on standard silicon photonics foundry process and magneto-optical thin film deposition. We successfully grow high quality MO garnet thin films on SiN with large Faraday rotation up to -5900 deg/cm. We show a superior magneto-optical figure of merit (FoM) of MO/SiN waveguides compared to that of MO/SOI in an optimized device design. We demonstrate TM/TE mode broadband and narrow band optical isolators and circulators on SiN with high isolation ratio, low cross talk and low insertion loss. In particular, we observe 1 dB insertion loss and 28 dB isolation ratio in a SiN racetrack resonator-based isolator at 1570.2 nm wavelength. The low thermo-optic coefficient of SiN also ensures excellent temperature stability of the device. Our work paves the way for integration of high performance nonreciprocal photonic devices on SiN platforms.