Research On Optical Bistability And Multi-stability Of Diamond-germanium Vacancy Color Center By Quantum Coherence

The quantum coherence effect induced by laser,which could dramatically changes the dispersion,absorption and nonlinear characteristics of the medium,has important influence in the nonlinear optics,laser physics and quantum optics fields.Optical bistability(OB)has attracted many researchers due to its potential wide applications in optical transistors,photoelectric conversion,storage elements,all-optical switches and logic circuits in recent years.In this paper,optical bistability and optical multistability(OM)behaviors are investigated theoretically in a four-level N-type diamond Germanium-Vacancy(GeV)color center scheme immersed in a unidirectional ring cavity based on electromagnetically induced transparency(EIT)under the semi-classical theoretical background of the light-matter interaction.The paper is mainly divided into the following parts:In the first part,the research background and current situation of optical bistability are introduced,firstly.Then,the research progress of optical properties of Ge vacancy color center system is introduced in detail.This may be helpful to the realization of optical bistability due to the excellent optical properties of Ge vacancy color centers and the non-linearity of single photon level.In the second part,the theoretical basis of the light-matter interaction is introduced.Especially,the physical methods and principles used in the research process of this paper are discussed in detail,including rotating-wave approximation,slow varying envelope approximation,probability amplitude method,density matrix method,theory of light evolution in atomic media and electromagnetic induced transparency.In the third part,the basic principle and classification of optical bistability are introduced,firstly.Then the mechanism of quantum coherent induced optical bistability is discussed in detail.This paper mainly describes our research work:Optical bistability and multistability induced by quantum Coherence in diamond germanium-vacancy color centers.The fourth part summarizes the research content,and the prospect of future scientific field theory and application of optical bistability and multi-stability in gennanium vacancy color center are made.The main results of our work are as follows:It is found that OB behavior is very sensitive to the system parameters,such as the detunings of probe and coupling fields,and the intensities of coupling fields as well as the density of GeV centers,and the thresholds of OB can be controlled via changing these parameters.In addition,we can switch OB to OM by adjusting the intensity of control field and the density of GeV centers or vice versa.The innovation of this paper:This work is of great significance.Compared with other diamond vacancy color centers in the past,the optical properties of germanium vacancy color centers have more advantages.Our study results are not completely consistent with the results of previous optical bistability research schemes in N-type atomic systems.A detailed and accurate data scheme is given for the experimental conditions of realizing optical bistability and multistability and their manipulations.The manipulation of the number density of germanium vacancy on optical bistability and multistability is also discussed,which will provide some theoretical guidance for the researchers to select better nonlinear materials when realizing the application of optical bistability correspondence in the future.