Design of a Refractive Index Plasmonic Sensor Based on a Ring Resonator Coupled to a MIM Waveguide Containing Tapered De
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Design of a Refractive Index Plasmonic Sensor Based on a Ring Resonator Coupled to a MIM Waveguide Containing Tapered Defects Mahdiye Rahmatiyar 1 & Majid Afsahi 1
&
Mohammad Danaie 1
Received: 1 May 2020 / Accepted: 15 July 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this paper, a novel nanoscale refractive index sensor topology, which incorporates a ring resonator containing circular tapered defects coupled to a metal-insulator-metal (MIM) plasmonic waveguide with tapered defects, is proposed. For the proposed design, the effect of introduction of defects on transmittance value, shape of magnetic field, and sensor parameters such as sensitivity (S) and figure of merit (FOM) are investigated numerically and simulated using finite-difference time-domain (FDTD) method. By optimizing the ring radius and selecting the appropriate waveguide width, we have achieved a maximum sensitivity of 1295 nm per refractive index unit (RIU) and a fairly high FOM equal to 159.6 RIU−1. The structure can be used as a high accuracy refractive index sensor for refractive indices ranging from 1 to 1.65. Due to the small size, wide detection range, and the high detection resolution of the proposed sensor, it is a good choice for integrated bio-sensing applications. Keywords Sensors . Surface plasmons . Refractive index . Photonic crystals . Ring resonators
Introduction Surface plasmons are electromagnetic waves propagating between metal and dielectric layers [1, 2]. They have found wide applications in non-linear optics [3], biomedical sensors [4], biosensors [5–8], optical and imaging circuits with high precision [9, 10], filters [11], etc. One of the types of plasmonic waveguides suitable for conducting SPPs is the metalinsulator-metal MIM waveguide [12–14]. They can produce a variety of combinations with other structures. They are used in many fields, including chemistry, physics, biology, and optical devices [15, 16]. These structures are often very small in size, which makes them easy to use for integrated circuits [17] and optical circuits [18, 19]; they also need an easy manufacturing process. At the same time, there is the widespread use of these waveguides for design of filters [20],
* Majid Afsahi [email protected] Mahdiye Rahmatiyar [email protected] Mohammad Danaie [email protected] 1
Electrical and Computer Engineering Faculty, Semnan University, Semnan, Iran
optical sensors [21, 22], mode converters [23], modulators [24], switches [25–27], couplers [28], demultiplexers [29–32], optical gates [33, 34], and so on. In the field of sensors, the refractive index (RI) sensors [35–37] resulting from the coupling of the MIM waveguide to the resonators perform very well in selecting the desired wavelength. Their superior parameters such as the sensitivity and accuracy of these structures, as well as their much smaller dimensions compared with other optical sensors, make them popular among researchers. Therefore, the extensive design of sensors including MIM wavegui
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