Study On Optical Response And Quantum Entanglement Based On Cavity Optomechanical System

As an interdisciplinary subject of quantum optics and mechanics,cavity optomechanical has attracted extensive attention.It has been widely used in various experiments due to its advantages such as scalability,high sensitivity and the ability to demonstrate quantum phenomena in macroscopic scale.With the help of optomechanical interaction,cavity optomechanical systems can produce many macroscopic quantum effects,such as optomechanically induced transparency,optomechanical entanglement,ground state cooling and squeezed state preparation of the oscillator,etc.As two important parts of the macroscopic quantum effect,optomechanically induced transparency and optomechan-ical entanglement have been widely studied.Optomechanically induced transparency is caused by quantum interference in the cavity field photon transition path with the same anti-stokes sideband path and frequency,which results in the weakening of the absorption ability of the system to the weak probe field.Optomechanical entanglement is a nonlocal and nonclassical relation between two or more quantum systems,and it is a mechanical property of the relation between subsystems or degrees of freedom in quantum systems.They have been widely used in many fields,which include optical routing,optical switch,optical frequency comb,fast-slow light effect,and high precision measurement.Optomechanically induced transparency provides an effective scheme for the conversion of classical and quantum information and it is also very important for the storage of optical information.In this thesis,we mainly investigate the optical response of cavity optomechaincal system on probe output field and the optomechanical entanglement between mechanical resonator and optical cavity.Initially,we study various characteristics of the probe output spectrum in the hybrid optomechanical system,including the normal mode splitting,the conversion between absorption and amplification behaviors,and the multi-optomechanically induced trans-parency and absorption effects based on the cavity optomechanical system.We discuss the effect of each subsystem on the normal mode splitting behavior and explain the linear variation of the distance between absorption peaks.In an experimentally feasible parame-ter mechanism,we find three critical points between absorption and amplification.Based on the first critical point,we study the effect of two-level atomic ensemble on absorption and amplification.The interaction between optical cavity mode and atomic ensemble not only splits the absorption peak,but also realizes the transition between absorption and amplification effect.In addition,the one-to-one correspondence location relations between the transparency dip and absorption peak for the double optomechanically in-duced transparency-like and optomechanically induced absorption-like,respectively,are also investigated.We conclude that the positions of absorption peaks and transparent dips induced by the interaction between the optical cavity mode and the two-level atomic en-semble are independent of the coupling strength,while which is linearly related to detuning parameter.In addition,we also use multi-energy level atomic ensemble to achieve the phenomenon of optomechanically induced transparency and optomechanically induced absorption.This provides a possibility to realize the optical frequency comb in the hybrid optomechanical system.In the following,we study entanglement characteristics of blue detuning mechanism in double cavity optomechanical system.It is well known that the optomechanical en-tanglement in the blue detuning mechanism has not attracted enough attention due to the limitation of system instability.The stability region of the system can be found in the red-detuning regime,because the red detuning laser can transfer the mean phonon number in the mechanical oscillator into the optical cavity mode,which achieves the cooling of mechanical oscillator.On the contrary,in the blue detuning mechanism,the entanglement cannot be realized due to system instability.In our system,by using the auxiliary optical cavity mode in red detuning mechanism,the stability of optomechanical system in blue detuning mechanism is achieved,so as to realize the optomechanical entanglement in the blue detuning mechanism.