High-sensitivity refractive index sensors based on Fano resonance in the plasmonic system of splitting ring cavity-coupled MIM waveguide with tooth cavity
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A metal–insulator–metal (MIM) waveguide with tooth cavity-coupled ring splitting cavity is proposed. Transmission characteristics and refractive index sensitivity are investigated by using finite-element method. A Fano-like line is observed in the transmission spectrum, and it is caused by the coherent superposition of the narrow discrete and wide continuous states. A maximum sensitivity of 1200 nm/RIU is achieved based on the Fano resonance effect when the air in the MIM waveguide and cavity is replaced by an insulator with a different refractive index. In addition, the derived structures of the plasmonic system are studied, and multiple Fano-like resonances are observed in the transmission spectrum. The effects of the structural parameters of plasmonic system on the Fano resonance are also investigated.
This work was sponsored by the National Natural Science Foundation of China (Grant no. 61605177), the National Science Fund for Distinguished Young Scholars (Grant no. 61525107), the Fund for Shanxi “1331 Project” Key subjects construction (1331KSC), the Natural Science Research Foundation of Shanxi Province, China (Grant No. 201701D121065), and the Open Project Fund of Science and Technology on Electronic Test and Measurement Laboratory (Grant no. ZDSYSJ2015003).
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Conflict of interest
The authors declare no conflict of interest.
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