| Multi-core micro/nano fiber is a kind of fiber waveguide with a cladding diameter of micron or nanometer.Owing to the strong evanescent field,it is very sensitive to the change of external parameters.Compared with common optical fiber sensors,the sensors based on multi-core micro/nano fiber have advantages as follows: high sensitivity,small size,multi-parameter detection,easy coupling with other optical waveguide devices,etc.This type of sensor has been paid more and more attention to the sensing applications of refractive index(RI),temperature,stress,acoustic wave,electric current,magnetic field and biochemistry.Therefore,the research on multi-core micro/nano fiber sensor has important theoretical value and practical significance.In this paper,the sensing characteristics of refractive index and temperature based on multi-core micro/nano fiber sensing structure are analyzed.The refractive index and temperature sensing characteristics of Mach-Zehnder interferometer(MZI)and Michelson interferometer(MI)based on multi-core micro/nano fiber are experimentally verified,which lays a theoretical foundation for the double parameter measurement and biosensor technology of multi-core micro/nano fiber.The main research contents of the paper are as follows:Firstly,the waveguide coupling characteristics and optical field characteristics of multi-core micro/nano fibers are analyzed by finite element method.Meanwhile,the propagation constants and coupling coefficients of double core fiber(DCF)and three core fiber(TCF)are calculated.Further more,the optical field characteristics,evanescent field ratio,refractive index and incident light wavelength characteristics of multi-core micro/nano fiber are calculated by optical software.The preparation process of multi-core micro/nano fiber is introduced.Secondly,based on the eigen equation of 2-Dimensional optical waveguide mode,refractive index sensitivity and temperature sensitivity of double core and three core micro/nano fibers are simulated and analyzed.MZI and MI based on multi-core micro/nano fiber are proposed.The refractive index and temperature characteristics of MZI and MI are verified experimentally.The experimental results are analyzed and high sensitivity refractive index and temperature sensing can be realized.Thirdly,according to the requirements of dual parameters sensing,MZI based on three-core micro/nano fiber cascaded with fiber Bragg grating(FBG)and FBG cascaded with MI based on three-core micro/nano fiber are proposed,which can realize the simultaneous measurement of refractive index and temperature.The refractive index characteristics and temperature characteristics of these two fiber sensing structures are tested.The experimental results verify the feasibility of using three-core micro/nano fiber for double parameter measurement.Finally,on the basis of the biological detection principle of the nanofilm modified three-core micro/nano fiber sensing structure,a three-core micro/nano fiber sensing structure based on 3-aminopropyltriethoxysilane(APTES)is proposed by the coupling characteristics of amino silane.The detection of the rabbit Ig G biomolecules is successfully achieved.The experimental results verify the feasibility of label free biosensor using three-core micro/nano fiber. |
