Imaging properties and phase relations in MMI devices with two-dimensional confinement

The imaging properties and phase relations of MMI devices with two-dimensional (2-D) confinement have been discussed in this paper. The self-imaging effect in 2-D MMI can be regarded as the superposition coupling of two orthogonal and independent one dimension self-imaging effect. Because of the coupling of two orthogonal and independent self-imaging effects and asymmetry structure in three-dimensional waveguide, it is obvious that the imaging characteristic of 2-D confinement MMI devices is provided with asymmetry characteristic. The formalism of 2-D confinement MMI phase relation is presented. The law of the imaging and phase relations depends on the waveguide structure and the propagation distances.