Investigation On Storage And Retrieval Of Weak Ultraslow Optical Solitons In Cold Atomic Media

With the development of human society, science and technology, people have put forward higher and higher requirements on high speed, efficiency and fidelity of information processing and transmission. The technology of magnetic information memorizing cannot satisfy the need of growing high-speed updating society. The scientists have shifted their focus to the research of the light memory, because of the high propagating speed and containing many information as one of the best information carriers. Recently the storage and retrieval of the light pulse via EIT is one of important, active and front research topics between light and quantum information processing.Electromagnetically induced transparency is based on the multiple-level quan-tum system where the controlling field is imported for a quantum interference effect and the implement of probe light field which excited quantum destruc-tive interference of the double paths in resonant medium, which eliminate the absorption of probe light field. EIT can greatly change the dispersion character-istic of the medium and enhance Kerr nonlinear effect, which have opened up a new way for nonlinear optics, especially the research of the nonlinear optics and their application under the weak light. Meanwhile EIT also provides the brand new technology for the precision manipulation of the atomic, molecule and pho-ton, for precision spectrum and precision measurement, for the processing and transmission of the light and quantum information.Up to now, the domestic and overseas research institutions have made great progress in the storage and retrieval of light pulse via EIT, but all these researches of light memory are based on the linear light pluses. Because EIT takes place in the resonant medium system between the light and quantum emitter(i.e. atom, molecule, quantum dot), there is great dispersion effects in EIT medium, which can result in the deformation and information’s loss of the pulse in the process of propagation. This is an urgent problem to realize the storage and retrieval of the light pulse with stable propagation, high efficiency, and high fidelity. The aim of this academic dissertation is to propose solutions of high efficiency and fidelity light memory via EIT. So the research method is using the Kerr nonlinearity of system to balance the dispersion effect, then we can get the stable weak ultra-slow soliton. At last, the high efficiency and fidelity storage of light pulse can be realized in multiple-level atomic system. In this paper, the research work mainly focuss on the following two aspects:1. The research on the weak ultra-slow soliton and their storage and retrieval in Ladder-type cold atomic system. Based on Maxwell-Bloch equations of the resonate interaction of the light and atom, we derive a nonlin-ear equation governing the evolution of probe field envelope with the singular perturbation theory. Then we prove that there is a balance between dispersion and nonlinearity in theory analyse and numerical simulation, and show that op-tical solitons with ultraslow propagating velocity and extremely low generation power can be created in the system. Furthermore, with Runge-kutta numeri-cal method, we demonstrate that such ultraslow optical solitons can be stored and retrieved by switching off and on a control field based on Maxwell-Bloch equations. The results show that the weak ultra-slow soliton can be stored and retrieved in ladder-type cold atomic system, and their storage and retrieval has high efficiency and fidelity. Last, we give a simple theory explanation analyzing the Maxwell-Bloch equations. This raises the possibility of realizing and applying the storage and retrieval of light and quantum information.2. We propose a theory scheme to realize storage and retrieval of weak ultra-slow vector optical soliton in a coherent atomic system working at the condition of double electromagnetically induced trans-parency. Firstly, Based on the Maxwell-Bloch equation of the system, which under consideration is a cold, lifetime-broadened four-level atomic gas with a tri-pod configuration, we drive the nonlinear equations of the two component of the probe filed and get many solutions of vector soliton with with the singular per-turbation theory. This coupled optical solitons not only have ultra-slow, almost same propagating velocity, but also have generation power. Then the storage and retrieval of weak ultra-slow vector optical soliton can be researched with the Runge-kutta numerical method based on Maxwell-Bloch equation. The result- s show that the weak ultra-slow soliton can be stored and retrieved with high efficiency and fidelity in four tripod-type cold atomic system. At last, The two component of light memory can be generalized to (N+1)-pod type cold atomic system. The result show that it is possible to achieve a memory of N-component optical soliton in a (N+1)-pod system (N>2) via EIT. The results reported here may have proposed the theory basis for of two (bit) or more component (bits) of light information memory with high efficiency and fidelity in.The theoretical research results proposed in this academic dissertation have a reference value and significance not only on the development of the weak non-linear optical theory and deep exploration of the physical effects, but also on the practical application and the experimental study of the processing and transmis-sion between the light and quantum information.