Microring-Based Optical Isolator and Circulator with Integrated Electromagnet for Silicon Photonics

In this study, we present optical isolators and circulators fabricated by bonding cerium-substituted yttrium iron garnet (Ce:YIG) on silicon microring resonators. A novel integrated electromagnet is fabricated by depositing a metal micro-strip on the bonded chip. We experimentally prove that it can be efficiently used to control the magnetic field needed to induce the nonreciprocal phase shift effect in the Ce:YIG. The fabricated devices exhibit extremely small footprint (<70 mu m) and can be packaged, eliminating the need of a large size permanent magnet. A large optical isolation of 32 dB and 11 dB is measured for the isolator and the circulator, respectively. Moreover, a two microring solution is also investigated to provide larger bandwidth and higher isolation. The proposed approach represents a promising solution for large-scale integration of nonreciprocal components in silicon photonics.