Research On Atomic Coherence Effect Based On A Degenerate Two-level Atomic System

The atomic coherence effect is the physical basis of laser birth,it is also an important basis for quantum communication and quantum storage.In recent years,atomic coherence has become an important branch of quantum optics and has been widely studied.Electromagnetically induced coherence and interference effects can be observed in almost all three-level ?-type or V-type structures.When the pump light wave and the signal light wave are under different polarization conditions,the electromagnetically induced coherence and interference effects in the three-level ?-type or V-type structure can also be achieved in a degenerate two-level system.For example,a right-handed polarization pumping light wave and a left-rotating polarization signal light wave are applied to a pair of Zeeman sublevels.The Zeeman level belongs to the ground state and the excited state of a two-level system and can be coherently coupled to the ?-type or V-shaped structure.At present,as an atomic coherence effect,electromagnetic induction gain(EIG)has gained widespread attention.Based on the foundation,the full text first introduced the basic concept and generation mechanism of electromagnetically induced transparent absorption and dispersion characteristics,electromagnetically induced absorption,atomic coherent four-wave mixing process,and reviewed the research progress and application in related directions at home and abroad.Based on this,theoretical and experimental studies of electromagnetically induced gain and four-wave mixing based on a degenerate two-level atom system are development.1)Theoretical and experimental analyses discuss electromagnetically induced gains based on a degenerate two-level atom system.An N-type degenerate two-level atom system is theoretically constructed to analyze the variation curves of the normalized transmission spectrum with the frequency detuning of the signal light passing through the helium atom media and the single photon resonance under different pump light-radiation frequencies.At the center,the Doppler broadening caused by atoms moving at different speeds is different,and the gain peak of signal light varies with ?p.Taking the degenerate two-level structure of Cs atomic momentum Fg=Fe as an example,the characteristics of the gain spectrum are analyzed,and the peaks of signal gain are compared with the pump light power and the temperature change of the Cs bubble.2)The four-wave mixing effect based on the degenerate two-level atom system is studied.The four-wave mixing process with stimulated emission under the transition of degenerate energy level is mainly discussed.In the experiment,the gain of the amplified signal light and the resulting conjugated light spectrum and the characteristics of the variation of the linear shape with signal photon detuning and the distribution of the change with the signal photon detuning are first observed.Using the self-assembling detection technique,we mainly measured the quantum noise correlation characteristics of signal light and conjugate light.We found that signal light and conjugate light are hot light fields,but under different signal-photon detuning,the noise intensity and intensity of the two are that also has certain associated characteristics.In the next step,we will theoretically analyze the quantum correlation characteristics of the stimulated radiation four-wave mixing process in a degenerate energy level system.