Study On Surface Plasmon Resonance Sensor Based On Few-mode Multicore Fiber

As a new type of optical fiber,Few-mode multi-core fiber(FM-MCF)has dual functions of space&mode division multiplexing,making it a new sensing medium.Surface plasmon resonance(SPR),as a highly sensitive sensing technology,has become a research hotspot in the measurement of physical,chemical as well as biological parameters.SPR sensors based on FM-MCF are used to measure external physical,chemical and biological parameters.On the one hand,the principle of external parameter sensing in new media is studied,and on the other hand,simultaneous measurement of several different parameters is realized.Therefore,a new seven-core few-mode optical fiber surface plasmon resonance sensor is proposed,and the sensing mechanism of metal thin-layer material induced surface plasmon resonance and gold nanowires induced local surface plasmon resonance(LSPR)are studied.Main work of this paper:1.In order to solve the problems of spectral broadening and low sensitivity of existing optical fiber SPR sensors,a FM-MCF SPR sensor is proposed to simultaneously detect multiple parameters.2.A SPR sensing model based on FM-MCF is established.The effects of residual cladding thickness,film material and transmission mode on surface plasmon resonance(SPR)are simulated and analyzed.When the thickness of the residual cladding is less than 1?m,the leakage evanescent wave can excite SPR very well.When the incident light wave is between 1 300 and 1 800 nm,only LP₀₁ and LP₁₁modes exist in the fiber.SPR can be realized in this band by setting indium tin oxide as surface plasmon material.The simulation results show that the sensitivity of SPR excited by LP₁₁ mode is higher than that of LP₀₁ mode.When 50 nm zinc oxide or 40nm titanium dioxide is used as modulation layer,the SPR peak can be moved to near infrared band and the original refractive index range can be broadened.3.A LSPR sensor model based on FM-MCF with air holes is presented.The effects of the size,shape,placement of single gold nanowires and the arrangement of multiple gold nanowires on the LSPR are studied,respectively.The influence of higher order modes on the sensitivity of LSPR sensors is further discussed.Through parameter optimization,when the diameter of gold nanowires is 150 nm and the distance between nanowires is 5 degrees,LSPR can be activated in the range of600nm and 1300 nm,and the average sensitivity of LP_02y mode is 5114 nm/RIU when the refractive index of the object to be measured is 1.33-1.38,and the maximum sensitivity is capable of reaching 7351.6 nm/RIU.