Wideband optical logic gates based on a 3×3 multi-mode interference coupler

In this paper, an all-optical logic gate with multiple functions and asymmetric structure is theoretically designed and simulated using a silicon on insulator (SOI)-based multimode interference (MMI) coupler. By switching the optical signal to different input waveguide ports, the device can function as an OR, NOT, NAND, or NOR gate simultaneously or individually. Simulation results by using three-dimensional beam propagation method (3D-BPM) incorporated with effective index method (EIM) show that these logic gates can operate with low loss in a wide wavelength band as much as 100 nm. It is a kind of promising device for applications on the next-generation high-speed, compact logic circuits, ultrafast signal processing as well as future silicon photonics-based integrated circuits.

I. Introduction

All-optical logic gates have attracted considerable research interests because of their numerous potential applications in optical signal processing systems, such as addressing and data encoding, or optical label recognition for optical switching [1]. Such logic gates become more important to cope with the ever-increasing bandwidth requirements of information signal processing systems for the future high-speed data computation and ultra-high capacity optical communications [2] [3]. The present data and signal processing is limited to the low speed of electronic logic circuits due to the presence of optical-to-electrical and electrical-to-optical conversions. This trend urges the development of highly-efficient, all-optical logics which could operate at high speed, wideband and low loss to avoid inefficient, low-speed optical-electrical-optical processes.