Design Of Refractive Index Sensor And Polarization Beam Splitter Based On Micro-Structure Optical Fiber

Because the structure of micro-structure fiber can be adjusted flexibly,it shows a series of excellent optical characteristics.With the improvement of manufacturing technology and research of micro-structure optical fiber,the research and design of various optical devices using micro-structure optical fiber has become a hot spot.At present,a series of devices based on micro-structure fiber have been reported,such as filters,sensors,wavelength converters,etc.In this thesis,a surface plasmon resonance(SPR)refractive index sensor and a polarization beam splitter based on micro-structure fiber are designed,respectively.The research contents and innovative achievements of this thesis are as follows.1.Design of micro-structure optical fiber refractive index sensor based on the SPR effectThe coupling and sensing characteristics of micro-structure fiber SPR sensor are investigated by full-vector finite element method.In order to enhance the strength of SPR,a kind of groove structure on the surface of D-shaped micro-structural fiber is designed,and a layer of metal is coated on its surface to form the surface plasma wave between the metal and analyte.In order to enhance the birefringence of the structure,two small holes are added in the core region of the designed micro-structure fiber.In order to achieve the higher sensitivity to the analyte with different refractive indices,the designed micro-structure fiber SPR sensor is simulated,and-dual-band measurement is carried out.The proposed micro-structure fiber SPR sensor achieves the maximum wavelength sensitivity of 2000 nm/RIU and 4000 nm/RIU in dual-band range of 0.75 to 1.0?m and 1.2 to 2 ?m,respectively.2.Design of the dual-core micro-structure fiber polarization beam splitter based on the coupling mode theoryThe coupling and propagation characteristics of the polarization beam splitter are investigated by using the full-vector finite element method.A polarization beam splitter is proposed,where the three layers of elliptical air holes are introduced to adjust the birefringence of the dual-core micro-structure fiber.The evolution process of the x-pol and y-pol polarized light in the cores A and B of the polarization beam splitter is simulated by using three-dimensional beam propagation method,and the correctness of the design scheme is verified.The simulation results show that when the fiber length is 254 ?m,the designed polarization beam splitter can achieve the complete beam splitting at wavelength 1.55 ?m.When the extinction ratio is below-20 dB,the bandwidth of the polarization beam splitter is 48 nm,covering the whole C band.The designed polarization beam splitter can be used as an important optical component in the laser and sensing systems.In this thesis,the flexible structure characteristics of micro-structured fiber are used to explore its applications in refractive index sensor and polarization beam splitter,and the micro-structured fiber refractive index sensor and polarization beam splitter are designed and investigated.The related research results can provide important reference value for the realization and application of integrated and high-performance micro-structure fiber devices.