An ultra-high sensitive plasmonic refractive index sensor using an elliptical resonator and MIM waveguide

In this paper, an elliptical resonator coupled to a straight metal-insulator-metal waveguide through a silicon layer is used for sensing application. The finite-difference time-domain method is used for the numerical investigation of the proposed structure. Such a structure demonstrates a multi resonance mode in the transmission spectrum. Based on the obtained results, the sensitivity can be reached to a value as high as 550 nm per refractive-index unit with a high FOM value of 282.5 RIU-1 around the resonance wavelength of 592 nm. In this structure, in addition to using a high Q-factor resonator, the resonance profile is localized and concentrated on the analyte to achieve an ultra-high sensitive refractive index sensor. Also, the effect of structural parameters on the transmission spectrum is investigated by sweeping them. Taking into account the obtained notable specifications such as ultra-high sensitivity and simplicity of the design and fabrication process, the presented structure can be employed in optical integrated circuits, particularly in high sensitivity sensors.