A High Sensitivity Index Sensor Based on Magnetic Plasmon Resonance in Metallic Grating with Very Narrow Slits

The index sensing characteristics of metallic deep gratings are numerically investigated. The concept is based on magnetic polariton resonance, which is very sensitive to changes in the refractive index of the surrounding medium. We numerically demonstrate that the sensitivity and figure of merit of the magnetic plasmon mode can be tailored by adjusting the depth and width of the slits. The highest sensitivity of 1542 nm per refractive index unit with a good figure of merit of 12.3 is obtained. The angle-insensitive property with a high signal intensity of this system could be useful for the future design and application of wide-range sensitive plasmonic index sensors.