The Properties Of Photonic Crystal Waveguide And The Keeping Wavwform Of Signal Propagation

Slow light is generated because of extremely strong material dispersion in the photonic crystal waveguide(PCW). It can realize optical delay line, optical buffers and data synchronization in all optical communications and information processing systems. However, the slow light region near the photonic band edge is usually accompanied by large group velocity dispersion (GVD) which severely deforms optical pulses and disturbs practical application. So how to reduce or eliminate the group velocity dispersion in the photonic crystal waveguide is very important. We investigate these as follows.Firstly, we optimize the PC W structure and analyze the bit rate of the signal. The slow light and group velocity dispersion properties of 2D triangular lattice photonic crystal line defect waveguide (PCW) with square and circular air-holes are analyzed. Adjusting two rows of the inner-hole adjacent to the waveguide and modifying the waveguide width can bring in low-group velocity and low-dispersion (LVLD) region, in which the group index of the square holes can reach 210 which is far better than the circular-holes. At the same air hole size and waveguide width, the PCW with the square holes supports higher bit rate of the signal almost 35Gb/s. These results provide important theoretical bases for the realization of optical buffering and optical logic devices in all-optical network.Secondly, we study the properties of the guide mode of slot photonics crystal waveguide. These rules perform greatly different from the conventional PCW and provide theoretical evidences for the structure optimization. Moreover, structure optimizations of slot PCW can also be used to compensate dispersion. We design a special structure to avoid the waveform broadening based on slot PCW. Then we calculated the bands model of the conventional PCW and slot PCW respectively. Negative GVD in the slow light region of the slot PCW is used to compensate the positive GVD of the conventional PCW. We designed the proper structure and plotted the waveforms of the light propagation in the PCW. We found that the waveform got broaden firstly for the positive GVD and narrowed down through the slot PCW for the negative GVD. When the energy fades away as the light propagated along the PCW, light can be well coupled into the narrow slot, because of the enhanced interaction between slow light and the low-index wave-guiding materials filled in the slot.Lastly, we numerically investigate the effects of position and radius disorder on the transmission spectrum of 2D hexagonal lattice photonic crystal waveguides (PCW) with different shapes of air-holes, including circular, square and elliptic. The disorder affect the anti-crossing point greatest. For different shapes of air-holes, we find that the square air-holes are more robust against the position disorder, especially in the slow light region. But the circular air-holes are better robust again the radius disorder. These disorders results provide important theoretical instructions for the imperfection during the manufacture possess in the PCWs'experiment and future applications in the optical network.