Study On Cooling Of A Mechanical Oscillator In A Coupled Cavity Optomechanical System

Cavity optomechanics is a new subject which studies the coupling interaction between mechanical and optical degrees of freedom.The interaction between the resonator and mechanical oscillator can be reflected by the cavity optomechanical system.At present,cavity optomechanics has evolved into a fast developing and highly focused frontier research field.The research in this field is closely related to optics,quantum physics,nanoscience,quantum informatics and other fields.Because of its irreplaceable unique advantages and application value in modern quantum science and technology such as precision measurement and highly sensitive sensing,it has always been the focus of research.In recent years,with the development and progress of semiconductor,laser technology,nanotechnology and material processing technology,the oscillator of the optomechanical system is gradually miniaturized,which provides an effective platform for observing the quantum effect and realizing the quantum manipulation of the quantum system.Through the coupled interaction between the optical cavity and the mechanical oscillator,many interesting nonlinear quantum optical phenomena can be observed in the cavity optomechanical system,such as optical bistability,optomechanically induced transparency,manipulation and preparation of quantum entangled states of the mechanical oscillator.However,due to the low frequency of the mechanical oscillator itself,it is easy to be excited and generate thermal noise under the influence of the external environment,which hinders our observation of the quantum effect.Therefore,cooling the mechanical oscillator has become the primary subject in our study of the cavity optomechanical system.Recently,scientists have made endless researches on the cooling of mechanical oscillators.In addition to the influence of the thermal noise of the coupling environment heat reservoir,the heating of the system caused by the quantum reaction force and the internal dissipation of the system itself will hinder the cooling of mechanical oscillators.Therefore,it is of great significance to further optimize the cooling effect on the basis of mechanical oscillator cooling.The main research contents of this paper are as follows:We mainly study the cooling of the mechanical oscillator in the coupled cavity optomechanical system including optical parametric amplification(OPA crystal).Two simple Fabry-Perot cavities interact with each other through linear coupling,and the mechanical oscillator and OPA crystal are coupled with only one of the cavity field modes.We first derive the quantum Langevin equation from the dynamic evolution equation of the system and the total Hamiltonian of the theoretical model.Using the average fluctuation theory,we can obtain the linearized quantum Langevin equation and transfer it from the time domain to the frequency domain.Then we derive the position fluctuation spectrum and momentum fluctuation spectrum of the mechanical oscillator,and obtain the expression of its temperature.Finally,we discuss and analyze the influence of different parameter coefficients on the cooling effect of mechanical oscillator.Our work provides a method and idea for cooling the mechanical oscillator in the compound cavity optomechanical system,and breaks certain restrictions,which is conducive to studying the quantum behavior of macroscopic objects at a deeper level,and has certain reference value for quantum information processing and quantum communication research.