Coupling in a twin-core photonic crystal fiber with metallic-coating

Abstract

In this project, we have developed a new kind of twin-core photonic crystal fiber (PCF) coupler device incorporating the plasmonics effect. Due to its stringent excitation criteria, plasmonics has been widely used for high sensitivity measurement and strong field localization. PCFs are a special class of optical fibers with periodic microstructured air holes embedded in a silica background material. These microstructures give us advantages such as great design flexibility, miniaturization and remote sensing capabilities over the conventional fibers. Therefore, we combine the merits of these two by introducing metal materials into the dielectric twin-core PCF and study the plasmonics influence on the coupling characteristics of the core-to-core energy transfer inside the structure. We investigate on different design configurations. The final optimized design structure demonstrates a coupling length reduction of 40 times over the one without metallic coatings, i.e. no plasmonics effect. The highest coupling efficiency can reach up to 73% and the insertion loss is as low as 1.3 dB, which are comparable with the literatures. However, this new type of coupler offers additional advantages of easy fabrication and mass production. The theoretical analysis in this report not only acts as a proof of concept but also leads the further exploration of light-plasmon interaction in general optical fiber devices for a variety of applications across different research fields. To our best knowledge, such a metal coated twin-core PCF coupler is being proposed for the first time. Its coupling characteristics with plasmonics enhancement have not been discussed before.