Abstract
Herein, a nanosensor structure is proposed, which comprises metal-insulator-metal (MIM) waveguide with stub and circular ring cavity with a stub (CRCS). The phenomenon of Fano resonance appears in the transmission spectrum, which is formed by interaction between the narrowband mode of CRCS and broadband mode of stub on bus waveguide. The influence of geometric asymmetry on mode splitting of Fano resonance was discussed. The mode splitting of Fano resonance can vastly improve figure of merit (FOM) with a sight decrease of sensitivity. The best performance of the refractive-index nanosensor is attained, which is 1420 nm/RIU with a high FOM of 76.76. Additionally, the application of designed structure on temperature sensing was investigated, which has sensitivity of 0.8 nm/°C. The proposed structure also possesses potential applications on other on-chip nanosensors.
Highlights
Surface plasmon polaritons (SPPs) are charge-density waves, which greatly decay in the direction vertical to the metal-dielectric interface so that they are largely trapped on the interface [1,2]
Fano resonance [20,21,22,23,24,25] is observed in plasmon coupled structures, which is generated by the interference between narrowband mode and broadband mode
In this paper, when the proposed structure serves as a refractive index sensor, its sensitivity can reach 1420 nm/RIU with an figure of merit (FOM) of 76.76
Summary
Surface plasmon polaritons (SPPs) are charge-density waves, which greatly decay in the direction vertical to the metal-dielectric interface so that they are largely trapped on the interface [1,2]. Metal-insulator-metal (MIM) waveguides, a kind of SPPs-based waveguides, have remarkable properties, for instance, easy manufacture, smaller dimension, stronger localized field confinement, shorter transmission length, and low propagation loss [29,30,31]. Yan et al [16] presented coupled structure of notched ring cavity and MIM waveguide with stub, whose sensitivity is 1071.4 nm/RIU with an FOM of 14.29. Wang et al [14] designed a nanosensor with sensitivity of 680 nm/RIU and FOM of 8.68, which comprises an analogy T shape cavity and MIM waveguide. In this paper, when the proposed structure serves as a refractive index sensor, its sensitivity can reach 1420 nm/RIU with an FOM of 76.76. A nanosensor structure is proposed, which comprises a MIM bus waveguide with stub and a circular ring cavity with a stub (CRCS). When the blood samples fill into the CRCS, the designed structure can act as a biosensor to detect the concentration of the hemoglobin level in the blood group
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