Controlling The Group Velocity Based On Nondegenerate Two Wave Coupling Like Mechanism

Controlling the group velocity is now a frontier of modern optics, the essence of which is the dispersive control. It is not only to help us to understand the characteristics of material, but also has much value for practical applications such as nonlinear effects enhancement, all-optical buffer and so on. Based on the work of M. S. Bigelow et al and G. Q. Zhang et al, the self-induced subluminal and superluminal light propagation were realized in ruby crystal experimentally and the nondegenerate two-wave coupling like mechanism (NDTWC-like) was proposed, with which the experimental results were explained. Based on the experimental work on ruby crystal, we speculated that the material with the nondegenerate two-wave coupling (NDTWC) process could be used to control the group velocity with the NDTWC-like mechanism. After that, the self-induced subluminal and superluminal light propagation was also achieved in rhodamine 6G-doped polymethyl methacrylate (R6G-doepd PMMA) with the NDTWC-like mechanism. We found that R6G-doped PMMA can be used as one of the good substitutes of ruby crystal to control the group velocity and confirmed the former suspicion that the material with the NDTWC process could be used to control the group velocity with the NDTWC-like mechanism. The main contents of the thesis are presented as following:1. In the chapter one, firstly, the basic concepts of the group velocity are introduced in general; secondly, the methods of controlling the group velocity are summarized; and then the significance of controlling the group velocity is introduced; finally, the applications such as all-optical buffer, nonlinear effects enhancement are introduced with great emphasis.2. In the chapter two, the work of M. S. Bigelow et al and G. Q. Zhang et al are introduced as background, respectively. Based on their work, the self-induced subluminal and superluminal light propagation in ruby crystal were observed by modified experimental setup and the work that controlling the group velocity in ruby crystal had been completed. The NDTWC-like mechanism was proposed to explain the experimental results and proved experimentally in ruby crystal. Because the physics essence of NDTWC-like mechanism and NDTWC mechanism is the same, we suspected that the material with the NDTWC process could be used to control the group velocity with the NDTWC-like mechanism.3. In the chapter three, the disadvantages of ruby crystal to control the group velocity were analyzed, and we made the R6G-doepd PMMA which was used as a substitute of ruby crystal. After getting the basic properties of this material, we proved the existence of NDTWC mechanism in the material, we experimentally observed the self-induced subluminal and superluminal light propagation, and presented the connection between the time delay and the modulation frequency. The contrast experimental results between the R6G-doepd PMMA and the pure PMMA supported our former suspicion that the material with the NDTWC process could be used to control the group velocity with the NDTWC-like mechanism.4. In the chapter four, the work was summarized. Based on what we achieved, firstly, we presented the further research plan of the NDTWC-like mechanism, and then the further research plan of controlling the group velocity in the total field.