Research On Nonlinearity Enhancement With Electromagnetically Induced Transparency

Since the first ruby laser being invented in 1960,nonlinear optics,an emerging discipline comes to our sights.More and more optical phenomenon relies on the nonlinear optics,such as optical rectification,the generation of higher harmonic,optical frequency mixing,self-focusing and the squeezed state of optics.All of them speed up the development of nonlinear optics.Moreover,a batch of new technologies are on the way,for example nonlinear laser spectroscopy and optical bistable effect.Electromagnetically induced transparency,an important quantum coherence effect,attract numerous researchers,since it was found.Because of the unique properties of absorption and dispersion,Electromagnetically induced transparency plays an important role in many physical problems.In addition,the application in the field of light stop refresh people's perceptions gradually.At the same time,the phenomenon in all-optical medallion,photon congestion,mechanical oscillator,etc,are also concerned.Because of the electromagnetically induced transparency effect,under the condition of weak light to have nonlinear enhancement is becoming possible.Various nonlinear enhancement scheme has been put forward.How to get a higher order nonlinear coefficient and how to get nonlinear enhancement under the condition of weak power with the absorption even vanished,become the research hot spot.In this paper,based on the work about electromagnetically induced transparency and enhancement and modification of the nonlinearity in our group,we made a theoretical and experimental research about fifth-order nonlinearity in a ? type three level system.Comparing the fifth-order nonlinear coefficient with and without atomic coherence,we find the atomic coherence can surely have an impressive effect on enhancement of high order nonlinearity.On the experiment,we set up the experimental platform,and the fifth-order nonlinear coefficient is measured using the method of cavity transmission spectrum,which have a good agreement with the theoretical calculation.What is more,we put forward a five level atom system,in which we can get a high nonlinear coefficient without absorption.The research can provide more innovative ideas in getting high order nonlinear coefficient and all-optics switch designing.