On-chip Ce:YIG/Si Mach-Zehnder optical isolator with low power consumption.

The integrated optical isolator is an essential building block in photonic integrated chips. However, the performance of on-chip isolators based on the magneto-optic (MO) effect has been limited due to the magnetization requirement of permanent magnets or metal microstrips on MO materials. Here, an MZI optical isolator built on a silicon-on-insulator (SOI) without any external magnetic field is proposed. A multi-loop graphene microstrip operating as an integrated electromagnet above the waveguide, instead of the traditional metal microstrip, generates the saturated magnetic fields required for the nonreciprocal effect. Subsequently, the optical transmission can be tuned by varying the intensity of currents applied on the graphene microstrip. Compared with gold microstrip, the power consumption is reduced by 70.8%, and temperature fluctuation is reduced by 69.5% while preserving the isolation ratio of 29.44 dB and the insertion loss of 2.99 dB at1550 nm.