Magneto-Optical Thin Films for On-Chip Monolithic Integration of Non-Reciprocal Photonic Devices.

Lei Bi,Dong Kim,Hyun Kim,Peng Jiang,Gerald Dionne,Mehmet Onbasli,Juejun Hu,Caroline Ross

doi:10.3390/ma6115094

Abstract

Achieving monolithic integration of nonreciprocal photonic devices on semiconductor substrates has been long sought by the photonics research society. One way to achieve this goal is to deposit high quality magneto-optical oxide thin films on a semiconductor substrate. In this paper, we review our recent research activity on magneto-optical oxide thin films toward the goal of monolithic integration of nonreciprocal photonic devices on silicon. We demonstrate high Faraday rotation at telecommunication wavelengths in several novel magnetooptical oxide thin films including Co substituted CeO2−δ, Co- or Fe-substituted SrTiO3−δ, as well as polycrystalline garnets on silicon. Figures of merit of 3~4 deg/dB and 21 deg/dB are achieved in epitaxial Sr(Ti0.2Ga0.4Fe0.4)O3−δ and polycrystalline (CeY2)Fe5O12 films, respectively. We also demonstrate an optical isolator on silicon, based on a racetrack resonator using polycrystalline (CeY2)Fe5O12/silicon strip-loaded waveguides. Our work demonstrates that physical vapor deposited magneto-optical oxide thin films on silicon can achieve high Faraday rotation, low optical loss and high magneto-optical figure of merit, therefore enabling novel high-performance non-reciprocal photonic devices monolithically integrated on semiconductor substrates.

Highlights

Nonreciprocal photonic devices, including optical isolators and circulators, are indispensable components in optical communications systems
We review our recent research activities toward monolithic on-chip integration of nonreciprocal photonic devices by developing high figure of merit (FoM) magneto-optical oxide thin films
For films grown on silicon or LSAT substrates, a systematic increase or decrease of the saturation magnetization and Faraday rotation was observed upon Ce4+ or Ga3+ substitution respectively as shown in Figure 4, indicating the strong dependence of the material magnetization on cation valence states

Summary

Introduction

Nonreciprocal photonic devices, including optical isolators and circulators, are indispensable components in optical communications systems. Nonreciprocal photonic devices based on polycrystalline garnet materials have been demonstrated on semiconductor substrates, including waveguide Faraday rotators [32], quasi phase matched magneto-optical waveguides [36,37,38,39] and magneto-optical photonic crystals [40,41,42,43,44,45,46,47]. Polycrystalline garnet films with high enough FoM on silicon, and novel waveguide-based nonreciprocal photonic devices such as optical isolators on a semiconductor substrate, are still challenging goals. We will review our recent research on developing high FoM magneto-optical oxide thin films toward monolithic integration of nonreciprocal photonic devices on silicon. For films grown on silicon or LSAT substrates, a systematic increase or decrease of the saturation magnetization and Faraday rotation was observed upon Ce4+ or Ga3+ substitution respectively as shown, indicating the strong dependence of the material magnetization on cation valence states. Further study on the MO spectroscopy of these films may provide more experimental insights to improve these oxide thin films

Polycrystalline BiYIG and CeYIG Films

A Nonreciprocal Ring Resonator Based Optical Isolator on SOI

Summary