Overlapping triangular resonator refractive index sensor based on MIM waveguide for solution concentration detection

Abstract

In this paper, we designed a high sensitivity refractive index (RI) sensor based on metal-insulator-metal (MIM) waveguide coupled overlapping triangular resonator working in the infrared region and having multiple modes. The effects of structural parameters on the transmittance spectra, magnetic fields and sensing inspection are investigated by finite element method (FEM). The results indicate that the sensitivity of the dual-overlapping triangular resonator structure can achieve 2760 nm/RIU with a corresponding figure of merit (FOM) of 65.03 RIU⁻¹ and Q-factor of 64.76 RIU⁻¹ by changing the system structure parameters. In addition, the symmetrical quad-overlapping triangular resonator structure exhibits superior sensing characteristics, delivering a sensitivity of 3330 nm/RIU accompanied by FOM of 68.12 RIU⁻¹ and Q-factor of 67.75 RIU⁻¹. Moreover, the proposed RI sensor demonstrates effective concentration detection capabilities for both glucose and plasma solutions with sensitivities of 0.33 nm/(L/g) and 0.47 nm/(L/g), respectively. Furthermore, the structure maintains high sensitivity across various solution detection applications.