Multimode interference structures – properties and applications

The aim of this paper is to present operating principles and properties of multimode interference (MMI) structures and their basic applications in optoelectronic circuits. We discuss the principles of direct, mirrored and multiple image formation for the general and restricted interference. We also show the possibility of self-imaging effects in gradient index waveguides. Based on the above, we present MMI applications in splitters and couplers N×M technology of different configurations, Mach–Zehnder interferometers (MZI) and phase shifters.