Bending loss analysis of multiple-slot waveguide microrings

Bending efficiency of three-dimensional bent multiple-slot waveguides are studied applying a combined method of effective-index and modified transfer-matrix methods. The effects of asymmetric structure (in which the widths of inner and outer strips are unequal), asymmetric slots (slots with different widths), and asymmetric middle strips (middle strips with dissimilar widths) on the bending efficiency are investigated. We show that the bending efficiency can be improved through the use of asymmetric structures and asymmetric middle strips. The bending efficiency of different slot waveguides (up to quintuple-slot structure) is compared. We reveal that although in general, single-slot waveguide provides the lowest bending loss for the same waveguide parameters; it is possible that multiple-slot waveguide can present a lower bending loss than the single-slot one.