Application Research Of Complex Defect Structure Of Two-dimensional Photonic Crystal In Terahertz Band

In this thesis,aiming at the existing shortages of meeting the requirements of the functional devices by using the defect structure of 2D photonic crystal,we derive and analyze the the photonic crystal band gap characteristic based on the principles of the band gap of photonic crystal.Further more,we calculate the relationship between the structure parameters and the band gap characteristic of typical square lattice and triangular lattice for 2D photonic crystal,and then the basic principles of choosing parameters in the design of 2D photonic crystal devices is proposed.We work over and compare the relationships between variety of defect structures and the THz functional devices,and then we design a 2D photonic crystal waveguide,a 90° bended waveguide,a T-shaped power divider,a directional coupler and different filters.The fuctuation of the coupling directivity in the whole band is less than ±0.5dB for the directional coupler and the bandwidth is 22.6%for the band pass filter,which are realized based on two special designed defect structures.Two different types of Photonic Crystal Fiber(PCF)made of polymer are researched based on the requirements of transmission and radiation.A 0.6THz photonic crystal fiber antenna is realized based on the single-mode resonance of the PBG-PCF,whose aperture efficiency can reach 73.6%.The suspended hollow-core PCF is designed based on the Total Internal Reflection(TIR),and then the wide band transmission character in THz band is demonstrated by designing and simulating some fibers working in different frequency bands.In addition,a waveguide-fiber coupler is proposed,which effectively solves the problems of coupling and connecting between the fiber and THz waveguide devices.The samples of the THz 2D photonic crystal devices and the polymer PCF are fabricated and measured.We fabricate the THz 2D photonic crystal waveguides and filters,which verify the theoretical calculation and analysis.Systematic study of the fabrication technology of the THz polymer PCF is carried out.We propose the improved method for the drawing process,fabricate the samples of the PCF,and build multiple THz test systems to complete the measurement.The 0.3THz PCF with standard waveguide port is realized for the first time and the minimum measured loss is 6.37dB/m,which lays the foundation for the further application of PCF.