Design of transverse electric ring isolators for ultra-low-loss Si3N4 waveguides based on the finite element method

In this Letter we present the design of a novel (to our best knowledge) integrated TE isolator realized using ultra-low-loss Si(3)N(4) waveguides. The device is made of two straight waveguides coupled to an array of ring resonators including a Ce:YIG garnet grown on their internal side. The analysis demonstrates advantages in loss, isolation, and passband width as the number of rings is increased.