Research Of The Characteristics Of Polarization Splitters Based On The Photonic Crystal Fiber

With the rapid development of artificial intelligence,big data and cloud computing,optical fiber communication technology plays an increasingly important role in information transmission.At present,the communication technology is moving towards high speed and high capacity,and the all-optical network becomes the key to solve the network security and satisfy mass information transmission.High-performance optical devices are needed for the high-capacity and ultra-high-speed all-optical network.As one of the important devices,the polarization splitter plays an important role in the construction of all-optical networks.Based on this background,this thesis carries out the research work.The unique and flexible design characteristics of photonic crystal fiber provide a solid foundation for optical devices with special properties,such as high birefringence,which makes the photonic crystal fiber polarization splitter is superior to the general optical fiber polarization splitter.In this thesis,high-performance polarization splitter is realized based on the photonic crystal fiber.By using the full vector finite element method,three different structures of polarization splitter are optimized and the performances are simulated and analysed.The main contents are as follows:(1)A polarization splitter based on silica is proposed and its cladding air holes are arranged in square structures.The length of the splitter is changed by coating gold film with the central air hole.The finite element method is used to simulate the structure and the capability of the polarization splitter is studied when the parameters take different values.By optimizing the structural parameters,a polarization splitter with excellent performance is designed.At the incident wavelength of 1.55μm,the polarization splitter with ultra-short length of 90.3μm and ultra-high extinction ratio of 135.1878 d B can be obtained.(2)A polarization splitter with chalcogenide glass as background material is designed.The cladding air holes are composed of lattice with different vertical spacing.A dopant is introduced into the central air hole to tailor the coupling characteristics,thus changing the coupling length.The effects of different parameters on the performance are investigated by the finite element method.The optimal length of the beam splitter is70.5μm,the extinction ratio is-96.1448 d B and the absolute extinction ratio is greater than 20 d B with the corresponding bandwidth 80 nm.It is concluded that the polarization splitter has good performance by discussing the fault-tolerant ability in the fabrication process.(3)Still the chalcogenide glass is used as background material,and a polarization splitter is proposed whose air holes with different sizes are arranged in hexagonal shape,and the elliptical air hole is introduced to obtain high birefringence.The structure is analyzed by the finite element method.The polarization splitter achieves an ultra-short length of 63μm,a high extinction ratio of 106.10 d B,and the bandwidth of 80 nm when the extinction ratio is greater than 20 d B.Meanwhile,the fault-tolerant ability is also discussed.The PCF polarization splitter can find good applications in optical communication and optical sensing areas because of its ultra-short beam length,high extinction ratio and large bandwidth.