A six-port circulator based on multimode interference

摘要

As a key nonreciprocal device, the optical circulator builds optical links to several terminals in a circulating manner. The waveguide-type circulator with port count more than four has not been discussed, mainly due to the strict phase matching and adjustment. In this paper, a six-port optical circulator is proposed by introducing the nonreciprocal phase shifts (NPS) into a 3×3 multimode interference coupler. The structure with Ce:YIG material bonded to SOI waveguide is employed to illustrate the implementation and do the device simulation. There is no complex phase matching in the whole design. Good performance can be expected with the present fabrication techniques. This design scheme can also be easily generalized to the circulators with even more terminals.