Nanoblocks-enhanced tunable plasmonic sensor based on MIM waveguide with double independent resonators

Abstract

A compact plasmonic sensor structure with silver nanoblocks enhancement is presented. The standard structure is based on the metal-insulator-metal (MIM) waveguide with a silver baffle, an elliptic ring cross cavity and a square frame cavity with a gap. The transmission characteristics of the structure are analyzed by the finite element method. The simulation results show that the structure generates triple Fano resonances. By changing the structural parameters of cavities, there is a good linear relationship between resonance wavelength and the effective length of resonator. Furthermore, the Fano resonances produced by various resonators can be tuned independently by the refractive index of the medium. The standard structure can achieve a sensitivity of 2760 nm/refractive index unit (RIU). By adding silver nanoblocks to the standard structure, the sensitivity of the modified structure reaches 3090 nm/RIU, which is 11.95 % higher than before. In addition, based on the independence of the resonator, the designed structure can realize the simultaneous detection of glucose solution and glycerol. The concentration sensitivities reach 388.7 nm∗ml/g and 403.3 nm∗ml/g, respectively.