Abstract
A finite-difference-time-domain (FDTD) approach is undertaken to investigate the extraordinary optical transmission (EOT) phenomenon of Au circular aperture arrays deposited on a Bragg fiber facet for refractive index (RI) sensing. Investigation shows that the choice of effective indices and modal loss of the Bragg fiber core modes will affect the sensitivity enhancement by using a mode analysis approach. The critical parameters of Bragg fiber including the middle dielectric RI, as well as its gap between dielectric layers, which affect the EOT and RI sensitivity for the sensor, are discussed and optimized. It is demonstrated that a better sensitivity of 156 ± 5 nm per refractive index unit (RIU) and an averaged figure of merit exceeding 3.5 RIU−1 are achieved when RI is 1.5 and gap is 0.02 μm in this structure.
Highlights
Surface plasmon resonance (SPR) is the resonant oscillation of free electrons excited by light at the metal/dielectric interfaces [1]
We report a novel device, which is composed of Au aperture arrays directly fabricated on the core-cladding Bragg (C-C Bragg) fiber facet and it is applied as an optical sensor based on extraordinary optical transmission (EOT)
We suggest that C-C Bragg fiber is the optimal structure
Summary
Surface plasmon resonance (SPR) is the resonant oscillation of free electrons excited by light at the metal/dielectric interfaces [1]. Over the past few years, many fiber-based SPR sensors have been reported, including SPR sensor configurations with multimode, single mode, and D-shaped fibers coated with a thin metallic layer [9,10,11] These kinds of sensors require a complex manufacturing process, and their sensing performances are not good. There have been many successful attempts to realize SPR based EOT sensors in optical fibers facet [12,13,14,15,16] These early proposals offer preliminary designs with little theoretical or experimental evidence to show that the sensing performance of optical fiber sensors would be enhanced by a metallic nanostructure.
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