Herein, a high-sensitivity multifunctional nanosensor comprising a metal-insulator-metal (MIM) waveguide and an inverted M-type cavity (IMTC) is presented. Fano resonances are generated owing to the interactions between different light pathways. Two contrastive structures are proposed to illustrate that a proper interference area leads to better propagation characteristics. The influence of geometric parameters on sensing properties is studied. Four derived structures are investigated to discuss the main factor for improving sensitivity. The designed structure can detect temperature and NaCl solution concentration with sensitivities reaching 1.444 nm/°C and 6.6 nm/%, respectively. The designed structures can also potentially be applied to other nanoscale devices.

Herein, a refractive-index sensor is theoretically proposed, which comprises metal-insulator-metal (MIM) waveguide and single rectangle cavity without a long side (RCWALS). The propagation characteristics were analyzed by finite element method (FEM). Compared with the contrastive structure, the designed single RCWALS structure has better transmission spectra and stronger resonance and supports Fano resonance. The effects of the structural parameters on sensing characteristics were investigated. Mode 1 of single RCWALS structure has better performance parameter, which is the best sensitivity of 1840 nm/RIU with a figure of merit of 51.11. Additionally, three derived structures are presented, which are composed of MIM waveguide and two RCWALS in different positions. They have lower sensitivity but better figure of merit, and provide more detection positions. The designed structures, which are greatly simple, can potentially apply to nanophotonics.