The Research Of Mechanism And Experiment For Surface Plasmon Resonance Sensor Based On Tilted Fiber Bragg Grating

TFBG (tilted fiber Bragg grating) and FBG (uniform fiber Bragg grating) are both belong to short period fiber gratings, the difference between them is that the grating plane of TFBG is not parallel to the cross-section of the fiber but is tilted by an angle. This unique structure of TFBG make it can couple the core mode to a series of contra-propagating cladding modes which can be used to excite surface plasmon wave. In this thesis, the transmission characteristics of the light wave mode in TFBG is analysised by the mode coupling theory firstly, deduced to the universality equations which be able to explain the mode coupling theory, and on this basis to establish the TFBG transmission model to analyze the sensitivity for the change of structure, temperature and the external refractive index. For the unique structure of TFBG, it is very suitable to be used as an optical couple device for a fiber optic SPR sensor.Surface plasmon resonance (SPR) sensor is a kind of optical transducer. It is based on the principle that the propagation constant of the surface plasmon wave propagating at the interface of a metal film and a dielectric is very sensitive to the Surrounding-medium Refractive Index (SRI). Commercialized SPR sensors based on bulk optical device such as prism have been available long ago. The research focus of SPR sensors now is to realize the miniaturization and microminiaturization of the SPR sensor system by utilizing optical waveguide as the couple device. This thesis proposed a new design of fiber optic SPR sensor based on tilted fiber Bragg grating (TFBG) after a comprehensive review of previous research work on the relative subject.The proposed TFBG-SPR sensor was fabricated by coating the cladding surface of TFBG with a gold film of which the thickness is about50nm. The cladding modes that fulfill some particular conditions will excite surface plasmon resonance at the gold-dielectric interface and lose their energy, and the energy loss will cause a change in the transmission spectrum of TFBG-SPR sensor. By interpreting the spectrum of TFBG-SPR sensor we can deduce the characteristics of the dielectric at the gold surface, and this is the sensing principle of TFBG-SPR sensor. Compared with the former SPR sensors based on fiber optic devices, the TFBG-SPR sensor does not require a modification of the fiber structure thus makes the manufacture process easier as well as maintains the robustness of the sensor.The steps of how to produce the TFBG-SPR sensor is detailed described in this thesis, then the TFBG-SPR biosensor was verified by series of experiments, and the application of the sensor is verified in practice.