Research On D-Type Fiber SPR Sensor Based On Grating Structure

The sensor fabricated by the combination of the fiber and surface plasmon resonance（SPR）technology has the characteristics of lightness,no marking,strong anti-interference ability and high sensitivity,which can be widely used in many fields such as biomedical,aerospace and petroleum industry.D-shaped fiber can be well combined with SPR technology due to its unique structure,which enhances the coupling between the core mode and the surface plasmonic mode,so as to improve the performance of the sensor.In this thesis,starting from different types of fiber,plasmon material selection and micro-structure design,several D-shaped fiber SPR sensors with grating structure are designed,in order to enhance the performance of the sensor.The model of D-shaped fiber SPR sensor is established by COMSOL Multiphysics simulation software based on finite element method,and its numerical analysis is carried out.The research results of this thesis are as follows:1.Firstly,a D-shaped fiber SPR sensor with platinum（Pt）grating based on single-mode fiber is designed.The effects of different combinations of Pt grating,alumina（Al₂O₃）film and graphene on the performance of the sensor are analyzed respectively.The results show that the addition of graphene and Al₂O₃layer can enhance the nearfield electric intensity of the Pt grating,thus improving the sensing performance.In particular,the figure of merit（FOM）of the designed sensor can be consumedly improved by the Al₂O₃-graphene-Pt grating hybrid nanostructure,up to432 RIU^-1,and it also has a maximum sensitivity of 11252 nm/RIU in the refractive index range of 1.33-1.41.2.In order to obtain the high sensitivity sensor,photonic crystal fiber（PCF）is replaced of single-mode fiber,and a D-shape fiber SPR sensor with Pt grating based on PCF is designed.The influence of the relevant parameters of air hole and grating on the performance of the sensor are analyzed respectively.Compared with the D-shaped single-mode fiber SPR sensor with Pt grating,the sensitivity of the sensor is obviously improved.The results show that the maximum sensitivity of the sensor is18700 nm/RIU in the refractive index range of 1.30-1.36.3.A D-shaped SPR sensor with gold（Au）grating base on PCF by using titanium dioxide（TiO₂）material is designed.The results show that after adding TiO₂material,the purpose of improving the sensitivity of the sensor can be achieved.Rabi-like splitting is realized by the introduction of a small air hole in the fiber,and a clear bimodal phenomenon is obtained in the near infrared band to achieve the dual-band detection,thus increasing the practicability of the sensor.Moreover,the influences of structural parameters for sensor are also analyzed systematically.Simulation results show that the two peaks have different refractive index detection ranges are 1.30-1.39 and 1.30-1.36 respectively,and their maximum sensitivity reach11400 nm/RIU and 26700 nm/RIU respectively.