Nonlinear Optical Effects In A Quantum Dot-cavity Coupling System

In recent years,the nonlinear optical effects in the cavity optomechanical system has attracted widespread attention from scientific researchers,and some gratifying results have been achieved.Typical cavity optomechanical system is composed of an optical cavity and a mechanical resonator.Generally,one side of the optical cavity is fixed,and the other side of the cavity mirror can vibrate along the cavity axis.Under the action of optical radiation pressure,the movable cavity mirror is simple harmonic vibration can be serving as a mechanical resonator.When the optical cavity is driven by a beam of laser,the cyclically vibrating light field in the cavity will generate radiation pressure on the mechanical resonator,causing the vibrator to deviate from its equilibrium position,so that the effective length of the cavity and the resonance frequency of the cavity will also change.This dynamic coupling causes a series of interesting optical effects.In this article,the quantum dot is trapped into the optical cavity,and a weaker pump light is applied to the quantum dot to form a quantum dot-cavity coupling system.The optical cavity is driven by a strong pump light and a weak probe light together.In the quantum dot-cavity coupling system,some nonlinear optical effects are discussed in detail,including optical bistability,four-wave mixing effect,and fast light and slow light effects.First,this paper studies the optical bistability effect in the quantum dot-cavity coupling system.The influences of the quantum dot-cavity coupling strength,the Rabi coupling strength,the quantum dot-pump detuning,the pump power and the cavity decay rate on the optical bistability are discussed in detail.Numerical calculation results show that when there are no quantum dot in the system,that is,when the quantum dot-cavity coupling strength is zero,not optical bistability occurs in the system;when the interaction between the cavity and the quantum dot is considered,optical bistability occurs in the system as the coupling strength between the quantum dot and the cavity gradually increases,and the bistable region gradually widens.At the same time,the study found that the coupling strength between the quantum dot and the cavity also affects the pump power threshold,as the coupling strength decreases,the threshold of the pump power is also reduced.By adjusting these parameters in the system,not only can the bistable behavior of the system be turned on or off freely,but also the range of the optical bistable area and the threshold of the pump power can be effectively controlled.Based on the optical bistable behavior in this system,an optical bistable switch can be realized,which has potential applications in quantum information processing.Secondly,the four-wave mixing effect in the system is discussed.The calculation results show that when the quantum dot-cavity coupling strength is greater,the system can generate a stronger four-wave mixing signal,and the greater the quantum dot-cavity coupling strength,the stronger the four-wave mixing strength of the system output;it is found that the four-wave mixing intensity can be effectively enhanced by selecting the optimal Rabi coupling strength and pump power;in addition,the cavity-pump detuning amount can be used to effectively control the intensity and peak position of the four-wave mixing.The results obtained in this research have potential applications in the fields of quantum optics and quantum information science.Finally,the fast light and slow light effects in quantum dot-cavity coupling system are discussed.In this system,by changing the quantum dot-cavity coupling strength,the conversion of fast light and slow light can also be achieved,but also converted.The calculation results show that in quantum dot-cavity coupling system,the Rabi coupling strength,the quantum dot-pump detuning,the pump power,and the cavity decay rate all play an important role in controlling the group delay time of the probe light.