Power splitting ratio couplers based on MMI structures with high bandwidth and large tolerance using silicon waveguides

We show that it is possible to obtain 2 × 2 couplers based on multimode interference (MMI) structures with nineteen new power-splitting ratios by cascading three or four MMI couplers. The other aim of this study is to use silicon waveguides, that are compatible with the existing CMOS (Complementary Metal-Oxide-Semiconductor) fabrication technology, for designing the proposed devices. The proposed MMI couplers with new power splitting ratios have simple geometries and low losses. These MMI couplers can offer valuable new possibilities for designing MMI waveguide-based photonic integrated circuits such as all-optical interconnects, microring resonators, clock distribution, Mach Zehnder Interferometer based on MMI couplers and other all-optical processing applications. The transfer matrix method (TMM) and modified effective index method (MEIM) along with the support of the 3D Beam Propagation Method (3D BPM) are used to optimize the proposed devices.

► This paper presents a new method for realizing new power splitting ratios based on MMI couplers.
► The new effective index method is applied to convert 3D structure into 2D structure.
► New MMI structures with new power splitting ratios can be useful for microring resonator based devices.
► Insertion loss, fabrication tolerance in width, length and positions of the access waveguides have been carried out.