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

Wei Yan,Weihao Yang,Shuyuan Liu,Lei Bi,Yan Zhang,Yucong Yang,Shuang Xia,Jun Qin,Longjiang Deng,Tongtong Kang

doi:10.1364/optica.408458

Abstract

Optical isolators and circulators are important components for photonic integrated circuits. Despite significant progress on silicon-on-insulator (SOI) platforms, integrated optical isolators and circulators have rarely been 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 MO thin film deposition. We successfully grow high-quality MO garnet thin films on SiN with large Faraday rotation up to - − 5900 d e g / c m . We show superior MO figure of merit (FoM) of MO/SiN waveguides compared to that of MO/SOI in an optimized device design. We demonstrate transverse magnetic (TM)/transverse electric (TE) mode broadband and narrowband 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 1570.3 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.

Highlights

Optical isolators and circulators are key components in photonic integrated circuits (PICs).They prevent the reflected light from adversely affecting the lasers and the optical system [1]
High performance, monolithically integrated optical isolators and circulators for both TE and TM polarizations on silicon nitride (SiN) have been experimentally demonstrated in this report
Ce1.4Y1.6Fe5O12 thin films are deposited on SiN with high Faraday rotation up to -5900°/cm at 1550 nm

Summary

Introduction

Optical isolators and circulators are key components in photonic integrated circuits (PICs). For MO isolators based on the nonreciprocal-phase shift (NRPS) effect, the low refractive index of SiN leads to much lower NRPS compared to SOI waveguides [28], placing significant challenges for fabricating a high performance MO optical isolator device on SiN. The much higher insertion loss of these devices compared to their counterparts on SOI was due to the relatively low magneto-optical effects of the Ce:YIG thin film, as well as the non-ideal device geometry It is still uncertain whether a high-performance optical isolator can be integrated on SiN. SiN isolators maintained a relatively stable operation wavelength within the temperature range from 20 °C to 70 °C, showing a small wavelength drift within 4 nm This value is smaller compared to a drift over 6 nm for SOI devices from 20 °C to 60 °C [46], due to the larger thermo-optic coefficient of Si (1.8×10-4/K) [48].

Conclusion

Findings

Methods