Magneto-optical Control And Its Application In Cavity QED Systems At Room Temperature

Cavity quantum electrodynamics(Cavity QED),mainly focus on the researches of the interaction between light field and atoms in a confined space.With the development of cavity quantum electrodynamics,cavity quantum electrodynamics systems are widely applied to quantum information and quantum physics,such as quantum entanglement,quantum states preparation,quantum communication,quantum measurement and so on.People study dynamics of cold atoms in a quantum cavity by using laser cooling technology.The laser cooling technology has such extremely stringent requirements for temperature that people gradually pay attention to room-temperature cavity QED system.In such condition atoms exhibit thermal motion,accompanied by obvious Doppler effect.Further researches show some ways to eliminate the Doppler effect.Combining them with magneto-optical rotation theory,we can construct a new cavity quantum electrodynamics system which can be used in not only weak magnetic detection but also the ultranarrow bandwidth optical filter.In this paper,we mainly introduce two specific cavity-atom systems respectively based on two different mechanisms.One is cavity electromagnetically induced transparency(EIT)mechanism,the other is active Raman gain(ARG)mechanism.Under the EIT mechanism,we propose a cavity QED system with two-photon Doppler-free configuration for weak magnetic field detection with high sensitivity at room temperature.Owing to the destructive interference induced by the control and driving fields,two transparency channels are opened.The Faraday rotation within two transparency channels can be used to detect weak magnetic field with high sensitivity at room temperature.The sensitivity with single photon and multiphoton probe inputs are analyzed under realistic experimental conditions.With single photon measurement,our numerical calculations demonstrate that the sensitivity with 3.8nT/(?)and 6.4 nT/(?)could be achieved.When we measure the magnetic field with multiphoton input,the sensitivity can be improved into 76.7 fT/(?)and 256.1 fT/(?).Comparing with previous weak magnetic detection with cold atoms,we find that weak magnetic detection at room temperature will obtain widely broader application.However,the EIT mechanism has some inherent drawbacks.Firstly,the EIT system is not able to eliminate completely the absorption in medium.Secondly,the probe field not only can be affected by a temperature-related Doppler effect but also faces significant attenuation or distortion under the room temperature.Thirdly,due to the ultraslow propagation,optical response time becomes longer.These drawbacks limit the potential applications of EIT system.However,ARG-based scheme can avoid these drawbacks.We study the three-level atom-cavity coupling system at room temperature based on ARG mechanism.We find the linewidth of cavity transmission spectrum is narrower than that based on EIT mechanism,and the transmission ratio of cavity is greater than 1.It means that detecting light obtains great amplification.The resonance absorption of detection light and the attenuation in medium are eliminated.In the system based on ARG scheme,the probe field avoids being affected by a temperature-related Doppler effect.Under the ARG mechanism we can obtain larger Faraday rotation angle than that of the EIT scheme.In addition we can change some physical quantities by adjusting the Rabi frequency of the control field and the physical quantity g(?)of cavity-atom system.Because of so many advantages of the active Raman gain scheme,it is applied to extensive field.For example,active Raman gain effect can produce great influence on optical soliton propagation;achievements of optical bistability and optical bistability in the medium based on active Raman gain;utilizing ARG scheme to adjust the self-steepening effect of optical pulse;taking advantage of active Raman gain mechanism to obtain great Kerr nonlinear effect and so on.ARG system also plays a great role in some weak light detection.The nonlinear effects of ARG system is widely used in optical quantum storage,quantum computing,weak light fast soliton,ultrafast optical soliton,nonlinear optical devices and so on.