Analysis of a Single Solid Core Flat Fiber Plasmonic Refractive Index Sensor
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Analysis of a Single Solid Core Flat Fiber Plasmonic Refractive Index Sensor Moutusi De 1 & Christos Markides 2 & Vinod Kumar Singh 1 & Christos Themistos 2 & B. M. A. Rahman 3 Received: 18 December 2019 / Accepted: 19 March 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this article, a single solid core flat fiber (SSCFF) refractive index sensor based on surface plasmon resonance (SPR) is proposed and analyzed numerically using the finite element method (FEM). The proposed flat fiber consists of a single array of five circular holes. Among them the central hole is made of GeO2-doped silica which is forming the core. Other holes are filled with air and situated symmetrically on both sides of the central solid core. The upper flat surface of the fiber is coated with a thin plasmonic gold layer which is protected by an active titanium dioxide layers. Analyte is situated on top of these layers. The wavelength interrogation technique is applied to study the coupling characteristics between the core-guided mode and the surface plasmon mode as well as for the refractive index measurement. Numerical analysis results show that this sensor is able to detect high refractive index analytes from 1.49 to 1.54 with a good linear response. Additionally, the dependence of surface plasmonic resonance wavelength on analyte refractive index is studied. The maximum wavelength sensitivity of this sensor is found to be 4782 nm/RIU with a high resolution of 2.09 × 10−5 RIU. The effects of different structural parameters on loss spectrum are studied in detail to optimize this SSCFF structure. In comparison to traditional PCF, this SSCFF structure is fabrication complexity free as well as a suitable candidate for developing portable devices and high refractive index analyte sensors, particularly chemical and protein sensors. Keywords Optical sensing . Photonic crystal fiber . Refractive index sensor . Surface plasmon . Finite element method
Introduction The exponentially increasing demand for portable highly sensitive sensors has given a new boost to the development of surface plasmon resonance (SPR)–based sensor technology. The SPR is a unique phenomenon in which electromagnetic wave is trapped between a single metal-dielectric interface. Also, energy is transferred from p-polarized light to free electrons at metal-dielectric interface via evanescent waves. SPR takes place at a particular frequency when the frequency of propagating light matches with the oscillating frequency of free electrons at the metal-dielectric interface. Then, surface
* Moutusi De [email protected] 1
Department of Physics, IIT (ISM) Dhanbad, Dhanbad, India
2
Department of Electrical Engineering, Computer Engineering and Informatics, Frederick University, Nicosia, Cyprus
3
Department of Electrical and Electronic Engineering, City University of London, London, UK
plasmon wave (SPW) propagates along the metal-dielectric interface [1, 2]. The nearby environment influences this trapped electromagnetic wave as
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