Optimal design and performance study of a low-index-contrast MMI optical coupler

The multimode interference (MMI) coupler is a versatile component for photonic signal processing applications. In present day, research scenarios based on low-index-contrast MMI couplers give more scope of study as it has certain advantages over high-index-contrast MMI couplers. In this work we presented an optimal design for the low-index-contrast MMI coupler. From various possible structures, we considered Silica-on-Silicon based 4×4 MMI coupler. Various techniques such as conventional self imaging, improved self-imaging and Genetic algorithm are used here, with numerical analysis such as mode propagation analysis, beam propagation method for evaluating optimal performance by adjusting the parameters of the structure. The optimum structure is finally selected one from them by comparing the results of these different techniques.