Design and numerical analysis of extreme sensitivity refractive index sensor based on cavity resonance mode with strong electric field

Relatively simple structures are necessitated for achieving high-performance refractive index sensors. Herein, we propose a less sophisticated sensing platform based on a thin metal film resonance cavity. A super-strong electric field in an analyte medium is formed via multi-wave interference, and the effective refractive index of the cavity mode strongly depends on the refractive index of the tested medium. In a relatively ideal situation, the sensitivity and maximum figure of merit of our device can reach 1,456,700 nm/RIU and 1,234,500 /RIU, respectively, which are both much higher than those of most sensing methods. This sensor shows great potential for low-cost sensing with high performance in biological or chemical sensing. Moreover, the cavity resonance configuration with high quality and strong electric field is versatile and may facilitate conventional surface plasmon resonance sensors in enhancing the strength of the detection field. Moreover, it can be applied to integrated optics and high-resolution spectroscopy.