Research On Nonlinear Optical Transmission Characteristics Of Multi-level Atoms And Atom-like Systems

Laser has become an indispensable tool for studying nonlinear optics because of its high brightness,high directivity,high monochrome and high coherence.The interaction between laser field and matter can induce quantum interference between different excitation paths of optical response.This quantum interference can change the absorption,dispersion and nonlinearity of the medium,which results in a series of novel optical effects such as electromagnetic induced transparency(EIT),enhancement of the Kerr nonlinear,coherent population trapping(CPT),lasing without inversion(LWI),vacuum induced coherence effect(VIC).Nonlinear optical properties based on quantum coherence control have very important research value and application value in quantum optics,nonlinear optics and quantum optical communication,and have become a hot research topic in recent years.In this paper,the nonlinear optical phenomena such as four-wave mixing(FWM),optical soliton and optical bistability(OB)in multilevel atomic and atomic-like systems are studied by using the semiclassical theory of the interaction between light and matter.1.A five-level asymmetric semiconductor double quantum wells system with resonant tunneling effect is proposed to study four-wave mixing process.The results show that a four-wave mixing generation field can be obtained by using two continuous-wave control fields and a weak pulse pump field in the system.Four-wave mixing process could be enhanced by resonant tunneling in such a quantum well scheme with low-pump wave intensities,thus improving the conversion efficiency of four-wave mixing.Especially for small propagation distances,a significant enhancement of four-wave mixing conversion efficiency can be achieved.2.We investigate the generation and propagation of optical solitons in a triangular quantum dot molecules scheme based on the tunneling induced transparency(TIT).In this system,the pump field is replaced by electron tunneling coupling,which can be modulated by the gate voltage.Double TIT windows appear due to the destructive quantum interference induced by the interdot tunneling coupling.Self-Kerr nonlinearity can compensate the group velocity dispersion,then slow optical solitons can be realized.Most importantly,our structure can provide two tunneling channels to support the propagation of slow optical solitons under the appropriate parameters.3.A theoretical scheme is proposed to investigate the formation of three coupled slow temporal vector optical solitons in a seven-state atomic system.By solving the probability amplitude equations describing the atomic response and the Maxwell equations under the slowly varying envelope approximations,we can obtain three-coupled nonlinear Schrodinger equations governing the evolution of the three polarization components of the probe field.Because of the quantum destructive interference caused by three strong continuous wave control fields,the absorption of the three components of the weak probe field is greatly suppressed while the large nonlinearity is obtained to balance the group-velocity dispersion,which ensure the formation of three coupled slow temporal vector optical solitons.In addition,the atomic system allows the existence of various types of three coupled vector temporal solitons,such as bright-bright-bright,bright-dark-bright,dark-dark-dark and bright-dark-dark vector temporal solitons.4.Optical bistability behavior of a four-level asymmetric semiconductor quantum wells system interacting with a degenerate probe field and a control field in a unidirectional ring cavity is studied.The results show that the emergence and disappearance of optical bistability can be effectively controlled by adjusting the strength of Fano interference,and the threshold and hysteresis cycle of bistability can be controlled by changing the intensity of control field.The results also show that the system exhibits optical multistability in a certain range of the frequency detuning of control field,and switching between optical bistability and multistability can be controlled by adjusting the frequency detuning of the control field.