title: Extraneous self-imaging phenomenon with weak-guiding condition.
abstract: We discuss a self-imaging phenomenon in a multimode interference (MMI) coupler. From experiment, different self-images, which are undefined in MMI theory, are observed. These undefined self-images are named "extraneous self-images" (Ex_SIs) for convenience. To estimate the applicability of the Ex_SIs, the characteristics of both the single self-image (0 dB self-image, 0 dB SI), which is defined in MMI theory, and the Ex_SI are compared and analyzed through simulation and experiment. The results show that the Ex_SI has an imaging period that is the same as the 0 dB SI and that the excess loss and the extinction ratio of the Ex_SI improve more than that of the 0 dB SI as the imaging period increases.
authors: Communications Research Laboratory, Division of Electronics and Computer Engineering, Hanyang University, Seongdong-Gu, Seoul Korea. holyhjk@hanyang.ac.kr
authors: Jong-Kyun
authors: JK
authors: Hong
authors: Sang-Sun
authors: SS
authors: Lee
authors: Seung-Dae
authors: SD
authors: Lee