Study of highly sensitivity metal wires assisted photonic crystal fiber based refractive index sensor
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Study of highly sensitivity metal wires assisted photonic crystal fiber based refractive index sensor Umang Ramani1 · Hemant Kumar1 · Bipin K. Singh2 · Praveen C. Pandey1 Received: 22 June 2020 / Accepted: 20 November 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this paper, a photonic crystal fiber (PCF) sensor based on surface plasmon resonance is proposed for refractive index (RI) sensing with improved sensitivity and resolution. In this design, solid core PCF with three layers of holes is used. Instead of a coating metal layer, we have used two metal wires at both sides of the outside layer of fiber to originate surface plasmon resonance for detection of RI of analyte effectively. Design and analyses have been performed by a Full vectorial finite element method (FV-FEM). Metals Cu, Au, and Ag have been used as plasmonic materials that exhibit higher wavelength sensitivity 7300 nm/RIU, 6200 nm/RIU, and 6100 nm/RIU, respectively. For Cu metal, we observe maximum amplitude sensitivity 597 RIU−1 with higher resolution 1.36 × 10–5 RIU for refractive index of range 1.31–1.36. However, the average sensitivity for Cu, Au, and Ag are 4320 nm/RIU, 4275 nm/RIU, and 3950 nm/RIU, respectively. The effect of air holes along with metal wires for sensitivity is also investigated. In results, copper has provided better sensitivity as well as resolution for a long-range analyte for this proposed RI sensor. Keywords Photonic crystal fiber · Finite element method · Surface plasmon resonance · Sensitivity
1 Introduction A new technology based on surface plasmon resonance (SPR) has achieved rapid development in the last decades. Recently, SPR based optical fiber sensor has been attracted to 2 and also some toxic gases like NH3, H2S (Mishra et al. detect gases like Cl, H 2, and N 2014). It has also been used to analyze the quality of food, its composition, and the concentration of components (Malinin et al. 2012), biological materials, and toxic metals detection (Lee et al. 2009). In 1968, Andreas Otto devised a prism coupling setup based on attenuated total reflection (ATR) that enables the coupling of surface plasmon waves with the evanescent wave (Otto 1968). Kretschman modified such a device with a coated metal layer on the prism base. A metal layer is in direct contact with the dielectric medium of the * Praveen C. Pandey [email protected] 1
Department of Physics, Indian Institute of Technology (BHU), Varanasi 221005, India
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Department of Physics, University of Mumbai, Mumbai 400098, India
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smaller refractive index (Sharma et al. 2007). P-polarized light incident on the prism-metal interface through the prism at an angle greater or equal to θATR , the evanescent wave is procreated at the interface. Excitation of surface plasmon takes place at the same frequency for that propagation constant of the evanescent wave corresponds with that of surface plasmon. This method is suitable for SPR sensing, but
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