Study On Refractive Index Sensor Based On MIM Waveguide

Surface plasmon Polaritons(SPPs)is a special electromagnetic wave formed by the interaction between light and free electrons of metal surface.It propagates along the metal-medium interface and decays exponentially in the direction perpendicular to the metal-medium surface.Therefore,SPPs is localized at the metal-medium interface.Since SPPs can break the optical diffraction limit,reduce the size of optoelectronic device and improve optical integration effectively,it has a good application prospect in lithography technology,photoelectric detection,micro-nano sensing and so on.Among them,the metal-dielectric-metal(MIM)waveguide structure based on SPPs is widely used in the design of sensors,filters,optical switches and other micro-nano devices due to its small size and simple structure.In this paper,two kinds of micro-nano sensors based on MIM structure are proposed,and the transmission characteristics and sensing characteristics of the micro-nano sensors are discussed.The main contents of this paper include:1.A micro-nano sensing structure based on MIM with triple rectangle structure is proposed.The transmission characteristics and sensing characteristics are analyzed by finite element method.It is found that the resonant peak will shift to a certain extent with the change of the structural parameters,and the detection sensitivity will also change accordingly.When the number of coupling rectangular cavities is increased from two to three,the resonant wavelength in the transmission spectrum changes from1853 nm to 1905 nm,and the refractive index sensing sensitivity of the structure will increase from 2000 nm/RIU to 4325 nm/RIU,realizing the high sensitivity sensing effect.2.A small size micro-nano sensor based on MIM trapezoid and T structure is designed.It is found that the transmission characteristics of the structure can be effectively improved by adding small metal nanorods in the electric-field concentrated area to exert certain influence on the electric field,and the resonant wavelength and refractive index sensing sensitivity increase with adding of the number and size of the metal nanorods.When three square metal nanorods with 30 nm side length are added,the resonant wavelength in the transmission spectrum changes from 1548 nm to 3167 nm,and the sensitivity of the structure will also increase from 1520 nm/RIU to 5720nm/RIU.Furthermore,when the nanorods are designed to be rectangular,the tunable filtering function can be realized in a certain range by controlling the position and angle of the metal nanorods.The research work in this thesis has certain reference value for the design and research of micro-nano optical sensors and the realization of highly sensitive refractive index sensors.