Research On Ultrasnsitive Sensor And Optical Force Effect Of Magnetic Nanoparticles Based On Fiber Fabry-Perot Interferometers

Fiber-optic sensors have played an important role in practical project application due to their unique characteristics,such as compactness,immunity to electromagnetic interference and high sensitivity.New materials are invented,which is also an important thing to the progress of human being.Magnetic fluid(MF)is a kind of new nanomaterial,and it has both the fluidity of liquid and the strong magnetism of solid magnetic material.MF has already got application in human health and aerospace technology due to its particular physics character.In the thesis,the study is based on the optical interference technique and waveguide,a refractive index sensor consisted of parallel-connected dual Fabry-Perot interferometers(FPIs)is proposed.The sensitivity is improved through the Vernier effect.The open and closed cavity FPIs are made in two pigtails of an optical coupler and used as the sensing and reference units,respectively.The Vernier effect is realized by superimposing the reflective comb spectra of the dual FPIs,which have slightly different free spectral ranges.The stability,repeatability and temperature response of the sensing structures are investigated.Experimental results indicate that the proposed sensing structure features high sensitivity(30801.53 nm/RIU),good stability,quick and accurate measurement.Moreover,the optical force acting on the magnetic nanoparticles(MNPs)is investigated with magnetic-fluid-filled fiber-optic Fabry-Perot interferometer.The optical force originates from the output Gaussian beam out of single mode fiber.The shift of interference spectra is related with the local refractive index variation in the light path,which is assigned to the optical-force-induced outward movement of MNPs.The influence of MF's viscosity,ambient temperature and external magnetic field on the optical force is also investigated in details.The optical force on the MNPs is found to be repulsive and its magnitude is close to the static magnetic field binding force to MNPs.The movement of MNPs will become much more difficult when increasing the MF's viscosity;and the repulsive movement of MNPs is not affected in 25~55 ?.