Analysis of the fully destructive interference of overlapping-images in MMI couplers

Abstract

Based on self-imaging effect and overlapping-imaging properties of multimode interference couplers, the phenomenon of fully destructive interference of overlapping-images in MMI couplers is revealed, for the first time. The condition for overlapping-image fully destructive interference is derived. From the point of view of overlapping-image fully destructive interference, we explain the paired interference and the symmetric interference. The expressions of the positions and number of output images for two especial overlapping-images are also given. We prove that this kind of phenomena exists not only in the paired interference and the symmetric interference by way of an example. The influence of the positional number on the fully destructive interference images is also analyzed. And the guided-mode propagation analysis method is used to confirm the analytical results.