Design of multimode interference coupling structures for photonic integrated circuit applications

In photonic integrated circuits, coupling structures with polarization independence and low insertion loss between their access ports and optical fibers are increasingly becoming critical. Multimode interference (MMI) based couplers have these properties in addition to possessing good fabrication tolerance and stable splitting ratio. Symmetrical excitation of the multiple ports plays a significant factor that determines these structures for use in interferometric sensor applications. Studies on back reflected properties of these devices help in the analysis and understanding of their functions and are also addressed in the context of their suitability for sensor applications.