All-Dielectric Refractive Index Sensor Based on Multiple Fano Resonance with High Sensitivity in the Long-Wave Infrared Region

Abstract

In this paper, we propose an all-dielectric metamaterials structure which contains four asymmetric square holes in the unit cell to design a high-sensitivity refractive index sensor in the long-wave infrared region. Theoretical analysis of the electromagnetic field distributions shows that the four transmission dips originate from magnetic dipole, electric quadrupole and Toroidal dipole. And its position can be tuned by adjusting different geometric parameters, which can optimize the structure to obtain a narrower linewidth to improve the performance of the sensor. Finally, we evaluate the performance of the structure as refractive index sensor by changing the refractive index of the tested substrate. The results show the refractive index sensor has high sensitivity in the long-wave infrared region: the highest sensitivity is 2803 nm/RIU and the figure of merit will reach up to 350.