A novel, to the best of our knowledge, nanosensor based on a metal-insulator-metal
waveguide coupled to a double ring resonator is proposed. The spectral
characteristics are studied by finite element method, and a Fano
resonance (FR) formed by the interference of the narrowband mode and
the broadband mode is discovered. After analyzing the effects of
structural parameters on the transmission characteristics, the
structure is further optimized by adding a rectangular cavity inside
the ring cavity. The maximum sensitivity reaches 1885 nm/RIU with the
figure of merit (FOM) of 77. Additionally, a tunable multiple FR
system is realized through the derivative structure, which leads to
the splitting of the resonance mode and produces two new narrowband
modes. Their formation mechanism and performance are studied through a
normalized magnetic field distribution and transmission spectrum. The
designed structure with excellent performance can discover significant
applications in the future nanosensing domain.
Herein, a novel nanosensor consisting of a ring resonator with two rectangular stubs and a metal–insulator–metal waveguide with two triangular stubs is proposed. By adopting the finite element method, a Fano resonance is found in the transmission spectrum, which results from the coupling between the discrete narrowband mode and the continuous wideband mode. The physical mechanism is analyzed by the normalized magnetic field distribution, and the effects of structural geometric parameters on the transmission characteristics are studied carefully. The results demonstrate that the maximum sensitivity could reach 2660 nm RIU−1 with the corresponding figure of merit of 66.5. The applications of the structure for hemoglobin concentration detection and temperature measurement are discussed, and the sensitivity of the two applications can reach up to 2.524 nm·l g−1 and 0.831 nm °C−1, respectively. The proposed structure with extremely high sensitivity and compactness can provide an excellent case for designing high-performance integrated plasmonic devices.
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