Inter-dot Tunneling-controlled Dynamical Behaviors Of Optical Solitons In Three Quantum Dots EIT Medium

Global IP(Internet Protocol)traffic has increased dramatically over the past two decades.Cisco predicts that the global optical network will carry data traffic of 4.8Zettabyte(ZB)per year by 2020,nearly tripling from 1.7 Zettabyte in 2017.Therefore,it is urgent to solve the problem of communication capacity in communication equipment.Optical fiber communication system based on optical solitons is considered as an important means to realize ultra-long distance high-speed communication due to its high information carrying capacity,high fidelity and low relay.The propagation of optical solitons through the nonlinear interaction between light and matter is one of the important means of optical information.EIT(electromagnetically induced transparency)is considered to be an ideal optical soliton carrier due to its excellent nonlinear effect in weak light.However,the cold atomic EIT medium faces many obstacles in practical application because of the difficulty in gas medium integration,the difficulty in precise control of properties and the low temperature.Along with the development of semiconductor technology,semiconductor quantum dots is considered in the practical application by producing EIT effect is one of the ideal vehicle for the realization of optical soliton,not only because it has similar to cold atomic discrete energy levels,but also because of increasingly mature semiconductor technology allows by changing the experiment conditions to obtain qualified quantum dots,even by using a single quantum dots made by means of arrangement,stack the mutual coupling between quantum dots to obtain the required properties.Therefore,it is of great significance to study the regulatory effect of quantum dots on optical solitons for the high-speed development of optical communication in the future.The structure of the paper is as follows:In the first chapter,the research background of quantum dots is summarized,including the preparation method of quantum dots in experiment and related research in theory.Then the research on optical solitons in quantum dot EIT medium is briefly summarized.Finally,the basic theory and research method are introduced.In the end,the main research content and research results are briefly introduced.When the distance between quantum dots is small and under the condition of applied voltage,quantum dots are easy to form quantum dot molecules through the coupling of inter-dot tunneling.In the second chapter,we construct a four-level"?"-type three-quantum-dot molecule,and study the influence of inter-dot tunneling intensity on soliton propagation behavior by using the multi-scale method.The results show,when Te₃=0 meV,with the increase of Te₂,the group velocity of the soliton first increases then it decreases,and the amplitude of the soliton gradually increases from 0.Secondly,with Te₃=0.5 meV the group velocity first it increases then decreases with the increase of Te₂,but the peak value when Te₃=0.5 meV is one tenth of the peak value when Te₃=0 meV,and the amplitude of the soliton gradually decreases.Thirdly,the group velocity first increases then decreases with the increase of Te₂,and the peak value is slightly smaller than of Te₃=0.5 meV when Te₃=1meV,and the soliton amplitude first increases then decreases.Finally,the amplitude of the soliton increases then decreases with the increase of Te₂,and the inflection point moves slightly to the left when Te₃=1.5 meV.Then,in chapter 3,we construct a five-level M-type three-quantum-dot model:it consists of a beam of weakly linearly polarized light split into left-handed and right-handed polarized light under the action of a parallel magnetic field,and then interacts with the three-quantum-dot to form the model.Then the propagation behavior of the soliton in the system is analyzed by the multi-scale method,and it is proved that the system can form a vector optical soliton with stable propagation.When the initial phase difference is 0,periodic elastic collisions occur between the two soliton components.Increasing the inter-dot tunneling strength will increase the collision period of the soliton.When the initial phase difference is??/4??/2 and ?,the two soliton components show repulsion,and increasing the inter-dot tunneling strength increases the repulsion force between the solitons.Finally,we summarize the influence of inter-point tunneling in the EIT medium on the dynamical behavior of solitons,and look forward to the future work of inter-point tunneling in quantum dot molecules in the field of optical soliton communication.