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

Hyuntai Kim,Yoonchan Jeong

doi:10.1109/jqe.2020.2968854

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.

Highlights

S URFACE plasmon polaritons (SPPs), a group of collectively oscillating electrons at a dielectric-metal interface, have been extensively studied thanks to their extraordinary physical characteristics and their high-end applications [1]–[8]
To justify how surface plasmon polariton (SPP) are generated under the metal-coated angled fiber facet (MCAFF) scheme, we have performed numerical simulations based on the finite element method (FEM: COMSOL Multiphysics®)
The TLT-MCAFF configuration dramatically helps suppress the SPP decoupling loss, so that we have numerically verified that an optimized TLT-MCAFF parameterized with t1 = 20 nm and t2 = 80 nm can yield SPP coupling efficiency of up to 72.93% at the distance of 5 μm from the center of the core of the MCAFF

Summary

INTRODUCTION

S URFACE plasmon polaritons (SPPs), a group of collectively oscillating electrons at a dielectric-metal interface, have been extensively studied thanks to their extraordinary physical characteristics and their high-end applications [1]–[8]. As their wavenumbers are invariably larger than their free-space counterparts, SPPs are normally generated by means of very special coupling techniques [1], [2]. These conventional SPP-coupling schemes inevitably have considerable limitations in terms of compactness, flexibility, efficiency, controllability, etc. Extending our numerical model to a dual-fiber platform, we rigorously characterize a novel fiber-in-fiber-out (FIFO) platform for plasmonic interconnection and sensing

GENERATION OF SURFACE PLASMON POLARITONS

Numerical Simulations

Experimental Proof-of-Principle Test

TWO-LEVEL-THICKNESS MCAFF

Findings

CONCLUSION