Photonic Crystal Characteristics Of The Space Optical Communication Applications

Photonic crystals are artificial structures in which the dielectric constant changes periodically. Photonic band gap is the distinct character of photonic crystal. Since the discovery of photonic crystal more than decades ago, the research on them has made rapid and steady progress. They have great charming characteristics compared with the traditional material, which may eventually pave the way for the next generation optical communication systems.With the development of the free space optical communication (FSO), they have strong requirement for the miniature of communication system. The requirement will be satisfied effectively if we make use of the photonic crystal in the process of designing the communication system.In our study, the characteristic of photonic crystal are studied by means of plane wave method (PWM), finite different time domain (FDTD) and transfer matrix method (TMM).The research on the application of the FSO has been done.The density of mode for HML structure with N periods is derived. Comparing with the transmission spectrum which got owing to TMM, used the TMM, we get the conclude that the one-to-one correspondence between the density of mode and the transmission spectrum. Optimize designed holophote in 1D photonic crystal for the wavelengthλ= 860nm has been done.The 2D photonic crystal band gap structures are derived and analyzed using PWM. The general computational routines are programmed to calculate photonic crystal band gap using MATLAB. The influence of changing lattice structure, permittivity and filling contrast for photonic crystal band gap has been researched. The defect model and the band structure with the point defect and line defect of 2D photonic crystal are discussed.The plane wave expansion (PWE) method was used to get the three dimensional band diagram and equifrequency surface (EFS). From the EFS, the maximum flatness half width (MFHW) and its position were got. The relation between MFHW and filling fraction P_f , dielectric ratioε_b/ε_a are given in order to get the optimal structure we employ in this paper. Optimize designed super-collimation in 2D photonic crystal for the wavelengthλ= 860nm has been done.