Metal-Coated Fiber-Optic Platforms for Surface Plasmon Polariton Generation and Interconnection

Abstract

We analyze a novel metal-coated fiber-optic platform for surface plasmon polariton (SPP) generation and interconnection. It is based on a metal-coated angled fiber facet (MCAFF), which enables alignment-free and unidirectional SPP generation from a fiber-optic mode with high conversion efficiency. We verify its functionality by means of both numerical simulation and preliminary experiment. We implement a two-level-thickness (TLT) configuration into the MCAFF to maintain its high optic-to-plasmonic conversion efficiency: The thin metallic layer just above the core region efficiently generates SPPs whilst the thick metallic layer beyond the core region enables its low-loss propagation by diminishing decoupling possibility into the dielectric region. We moreover devise a fiber-in-fiber-out (FIFO) platform that consists of a pair of TLT-MCAFFs. We numerically verify that it can yield more than 60% of FIFO coupling efficiency. We further show that the transmission spectrum of the FIFO-MCAFF is highly correlated with the refractive index of the top layer put on the metallic layer, and that it can be exploited to sensing applications that is required to measure and identify delicate changes in the refractive index of the top-layer material. We expect that the proposed metal-coated fiber-optic platforms will provide an efficient way to SPP generation and interconnection, and also has great potential to be novel sensing platforms for gas- or liquid-phase volatile substance.