Study On Optical Bistable Characteristics Of Quantum-coherently Controlled Multi-level Atomic Systems

Quantum coherence and interference in multi-level atomic systems can bring about many interesting optical phenomenon,such as:electromagnetically induced transparency(EIT),lasing without inversion(LWI),coherent population trapping(CPT),optical bistability(OB)and so on.Because of OB has many potential wide applications in all-optical switches,memories,and optical transistor,many researchers have paid much attention to OB in both the theoretical models and the experiments.Based on electromagnetically induced transparency(EIT),our main work is investigating optical bistability and multistability behaviors in a tripod four-level atomic configuration.The details mainly include the followings.Firstly,we mainly introduce the research review of electromagnetically induced transparency(EIT)and optical bistability(OB)based on quantum coherent.Secondly,we recommend the basic theory of light field interacting with matter,which contains the three basic pictures of quantum mechanics,dipole approximation,probability amplitude equation,rotating-wave approximation,density matrix equation,slowly varying envelope approximation,and the principle of electromagnetically induced transparency(EIT).Thirdly,in the first place,the concept and the mechanism of optical bistability,semi-classical theory of optical bistability are briefly described.Then,based on the principle of electromagnetically induced transparency(EIT),a tripod four-level atom scheme is proposed where the optical bistable(OB)and optical multistability(OM)phenomenon are discussed.It is found that in the tripod four-level atomic system,the energy levels and the applied fields form a loop system,by adjusting relative phase between driving fields we can effectively change coherence of the system,therefore,we can control the appearance of optical bistability and threshold of optical bistability adjusting relative phase.Moreover,adjusting relative phase,we can achieve optical multistability(OM),and switch optical bistability to optical multistability or vice versa.At last,we give a summary of this paper,and prospect the application of optical bistability in future science and reality.