Design of a multi-bits input optical logic device with high intensity contrast based on plasmonic waveguides structure

Optical logic devices are the fundamental building blocks for optical computing. In this paper, a compact optical logic device based on plasmonic waveguides is designed and investigated numerically. The proposed structure consists of ring resonators coupled to a metal-insulator-metal(MIM) waveguide. The finite-difference time-domain (FDTD) simulation and coupled-mode theory (CMT) analysis both reveal that typical plasmon-induced transparency (PIT) phenomena can be observed when the refractive index of the rings is changed. Based on the proposed structure, 2 bits and 3 bits input optical logic devices with high intensity contrast ratio (ICR) are devised and demonstrated, while the output logic states “1” and “0” are represented by the high and low levels of optical power. By changing the incident light at different wavelengths, the proposed structure can implement the two basic functions of logical operation: AND gate and NOR gate. The proposed devices are suitable for on-chip optical computing and can also be used in wavelength division multiplexing (WDM) systems.