Double-Ring Resonator Plasmonic Refractive Index Sensor Utilizing Dual-Band Unidirectional Reflectionless Propagation Effect


In this manuscript, a plasmonic refractive index sensor with two sequential ring resonators is presented. Due to the dual-band unidirectional reflectionless light propagation phenomena, both the sensitivity and figure of merit are improved. The finite-difference time-domain (FDTD) method is used to simulate the structure numerically. Moreover, the device is investigated analytically, using the coupled-mode theory (CMT). A good agreement between the analytical and numerical results is observed. The proposed device indicates a high sensitivity of ∼1000 nm/RIU, a significant figure of merit of 133 RIU−1, and a large quality factor of 132.8 for sensing different materials with the refractive indices of n = 1, 1.2, 1.3, 1.4, 1.5, and 1.6. Also, the presented structure is investigated as a temperature sensor in which the sensitivity to the temperature changes is obtained as 0.41 nm/°C.

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Data Availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.


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Author information




All authors contributed to the study conception and design. Codes, methods, and analyses were performed by Narjes Amoosoltani. The first draft of the manuscript was written by Narjes Amoosoltani and Kolsoom Mehrabi, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Abbas Zarifkar.

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Amoosoltani, N., Mehrabi, K., Zarifkar, A. et al. Double-Ring Resonator Plasmonic Refractive Index Sensor Utilizing Dual-Band Unidirectional Reflectionless Propagation Effect. Plasmonics (2021).

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  • Refractive index sensor
  • Ring resonator
  • Coupled mode theory
  • Temperature sensor