Properties Of The Gap And Slow-light Waveguide Based On Photonic Crystals

With the rapid development of optical communication, increasing numbers of steps in the existing communications network have exposed their bottlenecks, such as the collection and storage of the signals, the signal processing and transmission. In order to solve the bottleneck problem, optical components which are highly integrated and controllable must be needed to replace the existing optoelectronic devices, which puts more requirements on the optical components used in optical communication. Slow-light waveguide based on photonic crystals shows many potential applications in the future all-optical networks, such as the delay for the optical pulses and tunable slow light, the delay of dynamic light pulse or the storage of signals in the field of optical communications. Slow-light technology can be used to signal delay, data cache, exchange and other sectors. Since the concept of photonic-crystal slow-light waveguide has been proposed, it is becoming an active research in the field of optical fiber communication.This article is focused on the issues of the band structures of photonic crystals and the properties of slow-light waveguides. We have designed novel photonic crystals with tunable absolute-photonic gaps. Meanwhile, we have proposed more optimized waveguide structures which show better performance than those demonstrated in references. Besides, tunable slow-light waveguide based on photonic crystal with the infiltration of liquid is studied, too, and the promising future for applications in all-optical networks is introduced. The whole text is organized as follows:In the first chapter the main role of slow light in future communication networks and the methods to obtain slow light are summarized. Moreover, the advantages with their shortcoming shown in the reported works are estimated. At the same time, we have introduced the latest progress on the slow-light waveguides based on photonic crystals and described the purpose and content of this research.The second chapter briefly introduces the concept of a photonic crystal, classification of a photonic crystal and the basic properties such as photonic band gap and photon localization. Based on this, we have forecasted the promising future of applications in future communication networks. Followed by some main methods: such as plane wave expansion method, time-domain finite difference method, the transfer matrix method and the scattering matrix method.In this chapter, based on the plane wave expansion method, we firstly have designed the model of a photonic crystal with crescent-like-shaped cross section. Based on the plane wave expansion method, the band structure is calculated. And we have demonstrated the dependence of the band structure on the distribution angle of the original cell.Based on the optimization for the band structures of photonic crystals, we have studied the slow-light performance of photonic-crystal waveguides with mirror symmetry. Results show that optimizing the distribution angle can modulate the band structure. As a result of this, we can achieve the best slow-light performance by the optimization of the distribution angle.In view of the introduction optimization of a line defect, in Chapter5, we have studied the properties of slow-light waveguide. Numerical results have shown that the slow-light performance of photonic crystals can be improved by optimizing the declination of the first and second row of air holes. Then, according to the coupled mode theory, we have explored the reason that the performance of slow light can be developed by the optimization of the declination.A novel method to control the properties of a slow-light waveguide is proposed. We have studied the dependence of slow-light performance on the temperature of the SL-009liquid crystal. This structure can be used to realize tunable photonic-crystal slow-light devices.