Study On The Properties Of Defect Modes In Photonic Crystals

Photonic crystal is an artificial material, and will play important role in optical communication systems in the future. The researches about photonic crystals could be generalized into two aspects: theoretical analysis and experimental test. In both of the two fields, the most important things are to analyze the properties of photonic crystal band gaps and defect modes. The photonic crystal defect modes have got more attention because of their extensive applications. As we have improved and controlled the electric conductivity of semiconductors by inducing impurities into them, we could improve and control the photonics movement in the photonic crystals by adding defects into the photonic crystals. Although the final purpose is to experimentally realize the right defect import, the precondition for achieving the goal is to have reliable theory for supporting. In this dissertation it is theoretically discussed that the defect modes change with the structure parameters of the photonic crystal varying. For one-dimensional photonic crystals are easily to fabricate and analyze, and at the same time, many conclusions from one-dimensional photonic crystals are valid or helpful for higher dimensional photonic crystals, this dissertation has choose one-dimensional photonic crystal as analysis object.The main contents of this dissertation are as following:1. Study on the properties of band gaps and defect modes in one-dimensional photonic crystals containing double-negative and single-negative materials. Negative- refractive index materials have got intensive attention in recent years, not only because they have many optical advantages (for example, they could form perfect lens) but also the photonic crystals containing negative index material could have many new and useful properties (for example, omnidirectional band gaps). There have been many researches about photonic crystals with negative index material, but none of them has touched on the photonic crystals composed of double-negative and single-negative materials. So in this dissertation, we have discussed the properties of band gaps and defect modes in one-dimensional photonic crystals containing double-negative and single-negative materials, and compared the results with that obtained in other researches. We have found that the new band gaps have the similar properties with those of zero-n gap and zero-?eff gap. The defect modes in the new gaps have very narrow transmission peaks, and the regular pattern of defect mode wavelength changing with the defect layer thickness adjusting is different from that happening in ordinary photonic crystals.2. Study on the optical sensing properties of the defect modes. Both the gap lateral and the defect mode location would change with the structure parameter of photonic crystal varying, and based on the law, we could obtain the information about the structure parameter variation by purposely observing the defect mode change. In this dissertation, by analyzing the regular pattern of defect modes changing with the defect layer thickness and refractive index, we have found the defect modes in one-dimensional ternary photonic crystals have higher sensitivity than the gap lateral for sensing the change of defect layer. What is more, by analyzing the regular pattern of defect modes changing with the defect layer thickness and refractive index, we have found the defect modes in the photonic crystals composed of double-negative and single-negative materials have higher sensitivity than the defect modes in one-dimensional ternary photonic crystals.3. Study on the bistability properties of the photonic crystals containing two nonlinear defect layers. Nonlinear optics is different from linear optics, for example, the refractive index of nonlinear material could be related to the field intensity ( Kerr effect), and so the incident intensity and the transmission intensity would have a nonlinear relationship in the photonic crystals containing nonlinear materials(optical bistability effect). In all discussions about optical bistability, the lower bistability threshold is used to be research hotspot. In this dissertation, we first analyzed the relationship between threshold and structure parameter in the photonic crystals containing only one nonlinear defect layer, and then discussed the relationship between threshold and structure parameter in the photonic crystals containing two nonlinear defect layers. The results have shown that the structure with two nonlinear defect layers has lower threshold than the structure with only one nonlinear defect layer. On the other hand, there are plentiful phenomenons about the bistability effect chaning with the structural parameter varying in the photonic crystal with two nonlinear defect layers, and we have analyzed these special bistability effects in details. 4. Study on the properties of slow wave structures realized in one-dimensional photonic crystals. Slow wave structures have been extensively discussed in recent years because of their huge application values in the optical storage, optical switch and etc. Usually the couple resonator optical waveguides in two-dimensional photonic crystals are used to realize the slow wave structure, however, we could slow down the light velocity by introducing periodic defect layers in one-dimensional photonic crystals. In this dissertation, we have analyzed the slow wave structures in one-dimensional photonic crystals, mainly discussed the regular pattern of guiding bands and group velocity changing with the defect layer adjusting, as well as the results of guiding bands and group velocity changing with introducing another new defect layer into the structure.