Quantum Optical Properties In Atom-Optical Cavity Coupling Systems

In recent years,the cavity optomechanical system formed by the coupling of mechanical oscillator and optical cavity has become an ideal platform for people to observe quantum phenomena and test quantum theory.Therefore,cavity optomechanical systems have received extensive attention both theoretically and experimentally.The most basic cavity optomechanical system is a nano-cavity coupled with one of the movable cavity mirrors,and the other cavity mirror is fixed.When a laser beam is used to drive the system,the radiation pressure formed by the reflection of light back and forth in the cavity causes the movable cavity mirror to deviate from the original position,and the change of the cavity mirror position in turn changes the effective length of the optical cavity so that the cavity membrane deviates from its natural frequency,thus altering the intensity of the light.Under the action of the laser,the motion of the cavity mirror interacts with the distribution of the field intensity in the cavity,resulting in some interesting nonlinear optical effects.In this paper,two different cavity optomechanical systems are investigated.In the first two chapters,the optomechanical system of the coupling between an optical cavity containing a second-order nonlinear crystal and a two-level atom is studied;The last two chapters study the same optomechanical system as the first two chapters,but one end of the optical cavity is fixed and the other end can move freely along the cavity axis,which can be regarded as a mechanical oscillator.Both systems are driven by a strong pump beam,a weak pump beam and a weak probe beam.The quantum optical properties in the two systems are studied,including the four-wave mixing effect and the fast and slow light effect,and the differences in the output fields of the two systems are compared and analyzed.Firstly,the four-wave mixing effect in the atom-optical cavity coupling system is studied.The calculation results show that placing a suitable second-order nonlinear crystal in the optical cavity can significantly enhance the four-wave mixing signal.Adjusting the cavity-pump detuning can not only control the intensity of four-wave mixing,but also realize the conversion of single-peak and double-peak.In addition,the cavity decay rate also has an important influence on the regulation of the four-wave mixing intensity.Secondly,the fast and slow light effects in the atom-optical cavity coupling system are discussed.Through the calculation,the transmittance gradually increases with the increase of the second-order nonlinear coefficient,and the fast-light effect and the slow-light effect can be realized by adjusting the second-order nonlinear coefficient.Therefore,the second-order nonlinear crystal not only has an important influence on the fast and slow light,but also can achieve high transmittance.Adjusting the cavity decay rate and the cavity-pump detuning can also achieve fast and slow light conversion and high transmittance.Then,based on the original model,we further explored the four-wave mixing effect in the atom-optical cavity-mechanical oscillator coupling system.According to the research,after adding the mechanical oscillator,the strength of the cavity-mechanical oscillator coupling can be adjusted to obtain strong four-wave mixing strength and control double peaks,and at the same time,the influence of the pump power on the four-wave mixing strength is enhanced.The intensity of four-wave mixing can also be controlled by optimizing the angles and coefficients of the second-order nonlinear crystal,or by adjusting the cavity decay rate and the cavity-pump detuning.Finally,we explore the fast-light and slow-light effects in the atom-optical cavitymechanical oscillator coupling system.According to the research results,it is found that the coupling strength of the cavity-mechanical oscillator plays an important role in regulating the transmittance and the fast light effect.By introducing the mechanical oscillator,the influence of the pump power on the fast light effect is strengthened.In addition,the angle and coefficient of the second-order nonlinear crystal,the cavity decay rate and the cavity-pump detuning also play an extremely important role in adjusting the fast light effect and the transmittance.