WIDE-ANGLE COUPLING TO MULTIMODE INTERFERENCE DEVICES - A NOVEL CONCEPT FOR COMPACTING PHOTONIC INTEGRATED-CIRCUITS

Extremely compact multi-mode interference (MMI) devices using central wide-angle coupling of input and output waveguides are proposed. It is shown that MMI can be used to change the propagation direction of lig ht without the need for corner mirrors or bent waveguides. The concept can also be used for very compact power splitters which are even smal ler than conventional MMI power splitters. Coupling between waveguides at wide angles is discussed and a number of regularities are found. T he results can be useful for the design of more compact integrated cir cuits by a reduction of the number of bent waveguides which usually ta ke up the: largest part of the area of a photonic integrated circuit.