Subwavelength plasmonic liquid sensor using Fano resonance in a ring resonator structure

Abstract A plasmonic Metal-Dielectric-Metal waveguide-based sensor with a radius of 0.44 μm is designed by generating Fano resonance in the device which consist of a gap in the main waveguide which acts like a Fabry-Perot structure and a micro ring resonator coupled to the main waveguide. The increased sensitivity of 1200 nm/RIU is achieved by optimizing the device parameters for different kind of liquids. Finite Element Method is used for complete study of the design. For analyzing the transmission modes in plasmonic systems, the normalized Electric Field distributions are calculated. Effect of different gap sizes, different coupling distances between ring & main waveguide and effect of different radius of ring on transmission and sensitivity of device for different liquids is also investigated. A large tunability of 740 nm in Fano peaks is achieved by changing the radius of the ring. The device results are useful in designing nanoscale and highly sensitive sensors for different liquids.