Optical Solitons In Electromagnetically Induced Transparency Media Of Untracold Atoms

Since entering the information age, the requests of information processing become higher and higher with the growing amount of information. Traditional information processing methods have gradually approached the physical limitation. So, it is the inevitable trend in information research to search for new information processing methods. With the significant advantage such as large information capacity, strong anti-interference ability and so on, optical soliton communication is considered as the preferred new approach of information processing. However, at present, most of optical soliton generation is based on traditional optical media. In traditional optics, the resonance media which can excitated significant nonlinear optical effect, go with the light loss for the strong resonance absorption of medium. And the non-resonant media can only excitated weak nonlinear, although the absorption is weak. So, in order to obtain optical soliton, high-intensity light source is needed. However, the thermal effect, cause by high-intensity light source, is not favorable to miniaturization and integration of information processing devices. In recent years, considerable attention has been paid to the study of electromagnetically induced transparency (EIT) medium based on quantum coherence. The main contribution is that significant nonlinear optical effects can be obtained, and the strong resonance absorption of medium can be inhibited. Therefore, it provides a possible way to resolve the problem mentioned above. Simultaneity, how to form optical soliton is also an interesting topic in EIT media, using the significant nonlinear optical effects in it to balance the dispersion (diffraction) effects. In recent studies, ones find there is a new type optical soliton in EIT media. It can occur under weak light condition and it's velocity lower than the vacuum speed of light several orders of magnitude. These results opened up a new field in researching the nonlinear optical properties in EIT media. It only consider single signal light propagate in one-dimensional EIT medium in the most of previous studies. Nevertheless, in the most practical condition, there are several optical fields propagate simultaneity or in high-dimensional media.In our paper, based on semi-classical theory, we study the dynamics of optical solitons in EIT media of untracold atoms, by using a multiple-scale method and numerical simulating method. We obtained a series of interesting results. The paper is arranged as follows: In chapter 1, the concept and classification of optical soliton are introduced at first. Then, we expound the basic principle of EIT and some study situation related to this thesis such as the ultraslow propagation property, the resonantly large nonlinearity enhancement, and so on. The main research contents, methods and significance of our thesis are shown at last.The most of previous studies only consider light propagate in one-dimensional EIT medium. But the fact is that light propagate in the high-dimensional one. Thus, we study the dynamics of the (2+1)-dimensional spatial optical soliton in a high-dimensional three-levelΛ-type atomic system via EIT media in chapter 2. The result shows the optical soliton is not stable, and can evolved with time into a ring dark soliton.In most cases, multi-beam signal light propagate in the same media simultaneity. The nonlinear propagation properties of two probe fields which propagate simultaneity in one system is studied in chapter 3. We show that a two-component SOS can be produced under the condition of a rather low input power. Meanwhile, by numerical simulating the interaction between them, we obtain that whether through repulsive or attractive interaction or elastic or inelastic collision, the energy transfer between the two SOSs are correlated with their phase shift.For an optical field is a vector field, in chapter 4, the scheme of five-level V-type atomic system via EIT is proposed with the aim of studying temporal ultraslow vector optical solitons (USVOS). We have demonstrated that the temporal USVOS can propagate stability. The results also show the collision characteristics between them are correlated with their phase shift and incident angleFinally, we give a simple summary about our study. And a further investigation about this frontier area of research is discussed.