Fabrication and comprehensive study of silicon oxynitride based compact directional coupler and multimode interference coupler

Abstract

In this paper a comprehensive study of compact conventional Directional Coupler (DC) and Multimode Interference (MMI) coupler using a numerical model based on Simple Effective Index Method (SEIM) have been presented. The coupling length of the couplers is then compared with the results obtained by using commercially available Beam Propagation Method (BPM) based software with respect to different waveguide separation gap and different coupling gap's refractive indices. The designed couplers are fabricated using SiON as a core and silica as a cladding. It is found both from the experimental and theoretical results that the beat length of conventional MMI coupler is ~ 1.9 times lower than that of conventional DC.