Triple narrow-spectrum enhanced multiparameter sensor based on asymmetric MIM waveguide for gas and liquid sensing

In this paper, an enhanced multiparameter sensor based on a metal–insulator-metal (MIM) waveguide structure with surface plasma polarization is proposed. We initially establish a coupling model consisting of a bus waveguide containing a barrier, and E-shaped and rectangular resonant cavities. It can generate asymmetric triple Fano resonance and achieve independent tuning of the resonance peaks by adjusting the geometrical parameters of the structure. By further analyzing this structure, it breaks the symmetry in the x-direction. The results show that the complexity and structural response time of the asymmetric structure in the X-direction increases considerably, and the transmittance appears to decrease significantly. This proposed waveguide structure is also applied in refractive index sensing with a maximum sensitivity of 2465.3 nm/RIU and a high linear correlation between the resonance wavelength and refractive index. The sensitivity of the structure for glucose solution and blood plasma reached 0.3238 nm∙L/g and 0.243 nm∙L/g, respectively, and the detection of methane was realized by covering a methane-sensitive membrane in the cavity of the structure with a sensitivity of −12.017 nm/%. The proposed method provides an important approach for designing nanodevices with narrow spectral enhancement and multiple channels. It can be applied to medical tests, optical sensing, and gas–liquid detection.