Research Of Bragg Band Gap And Analysis On The Optical Properties Of Two-dimensional Photonic Crystal Waveguide

Photonic crystals are the dielectric structure of refractive index periodic change in the spatial. When the light propagates in photonic lattices of the periodic arrangement, as the Bragg scattering of medium on the light at different media's interface, light will be modulated to form the band structure and resulted in photonic band gap between the band and the band. Electromagnetic waves are prohibited transmission when its frequency falls into band gap, or monochromatic light is diffracted along the Bragg angle propagation and completely deviates from the original propagation direction to form Bragg band gap. But photonic lattice with the photonic band gap can not effectively control the propagation of the light, we lead into defect in a perfect photonic crystal. When the frequency of light is equal with the photonic gap with defect model, it can be localized and transmit along it. In addition, inducing the photonic lattice by light-wave is the best method of all simple, convenient and low-cost one to investigate the band-gap and band structure. Researching different optical properties of lattice defects is prerequisite which achieves defect states photonic lattice to control light transmission. Therefore, it has played an important role in development and application of photonic lattice to research band gap location, bandwidth and point defects'implantation in the LiNbO3:Fe crystal.In this paper, we firstly investigated that how to find the position of band gap using Fourier transformation method of Amplitude mask in LiNbO3:Fe crystal producing photonic lattice and discussed the factors that affected Photonic bandwidth. Secondly, we broadened photonic band gap. Lastly, we studied how to implant point defects in LiNbO3:Fe crystal and discussed guiding light nature.The work I have accomplished mostly as follows: 1. Using Fourier transformation method of Amplitude mask, we have made one-dimensional photonic lattice in LiNbO3:Fe crystal and measured the band gap which met Bragg diffraction's condition by the transmission efficiency, analyzed the factors of affecting bandwidth in the angle domain.2. On the basis of obtaining band gap position and bandwidth, using Fourier transformation method of Amplitude mask, we discussed band-gap situation which the number of amplitude mask holes increased to five from three under the hole spacing of 6mm. We found the peculiar experimental phenomena:the number of diffraction reached to 4 from 2, so that the Bragg diffraction angle changed to be more, which improved the Bragg diffraction efficiency of the non-parallel light. However, the diffraction is angle separation,Bragg band-gap will be fundamentally broadened if the diffraction becomes angle continuity, which will greatly improve guiding light ability of the photonic crystal fiber. Based on this idea, we realized the widened band gap, using amplitude mask with the 4 holes and 2mm hole spacing. It provides an effective way for increasing the bandwidth. What's more, it plays a very important role in promoting the light energy utilization. That is a innovation in this thesis.3. Using cross phase method, we produced two-dimensional square lattice with point defects. By comparing the different experimental conditions, we found the best conditions for generating defect mode after leading into the point defects and gave theoretical explanation that two-dimensional defect structure localized very strong light wave. Experimental results show that light-wave can be localized by the defect and analyze it can not be ignored to the quality of local light phenomena and the merits of the lattice that irradiation time of defect and lattice, selection of o light and e light and the size of point defects.