Design And Wideband Slow Light Property Of Asymmetric Photonic Crystal Waveguides

The integration of optical devices is one of the inevitable trends of optical network development. In the achievement of optical network, optical buffering and all-optical signal processing are two critical technology. In recent years, with the development of research in slow light, slow light is considered to be a n effective solution to achieve optical buffering and all-optical signal processing. The results of slow light research tell us that the light pulse will be compressed during the transmission. Meanwhile, the light energy is increased and the corresponding linear and nonlinear optical effects are enhanced. Among the different solutions of achieving slow light, Photonic Crystal Waveguides(PCWs) have its advantages of small volume, high density integration, a large band width and low dispersion. Those advantages make PCW the best choice to achieve slow light.In this thesis, I start from the basic concept of photonic crystal and introduce the corresponding electromagnetic theory and numerical simulatio n methods. Then I design two new structures of photonic crystal waveguide and analyze their performance of slow light and dispersion detailedly. The full text of our research is as follows:Firstly, I deeply discuss the slow light theory and summarize the previous research results about slow light in photonic crystal waveguide. Based on traditional photonic crystal of circular air hole, through shifting two rows of air holes adjacent to the waveguide selectively, a new kind of asymmetric photonic crystal waveguide is obtained. I use a plane wave expansion(PWE) method to calculate the band structure o f this new asymmetric waveguide and analyze the dispersion characteristics. Four different structures of photonic crystal waveguide are achieved with large bandwidth and low dispersion. For those four structures, the average group indices of 41, 50, 68 and 114 are obtained with bandwidth over 12.3nm,11 nm,7.8nm and 4.7nm, respectively. The corresponding GBP indices are above 0.30 for all of the four structures. The low dispersion slow light propagation is confirmed by the simulation of temporal pulse-width spreading with the 2D finite difference time domain(FDTD) method. The corresponding results coincide with the previous prediction of PWE method. The low dispersion characteristics are also confirmed by the minimal pulse broadening in the time domain.Secondly, I discuss the Slotted Photonic Crystal Waveguides(SPCWs), which is widely researched recent years, and compare the slow light performance of different slotted photonic crystal waveguides. Then I design a new type of SPCW, in which the symmetry is broken by selectively shift two rows of air holes adjacent to the slot. Six different structures with wideband slow light are obtained. For the W1 mode slow light, the average group indices of 47,67 and 130 are obtained with bandwidth over 7.2nm,4.8nm and 2.3nm, respectively; For the slot mode slow light, average group indices of 42,55 and 108 are obtained with bandwidth over 6.2nm,5.6nm and 2.2nm, respectively. The corresponding results of the time domain simulation coincide with the previous prediction of PWE method. The low dispersion characteristics are also confirmed by the minimal pulse broadening in the time domain.