Research On Characteristics Of Thermophonon Flux In Coupled Optomechanical System

In recent years,the cavity optomechanical system which couples the optical mode with the macroscopic mechanical oscillator motion mode has attracted extensive attention.Various macroscopic quantum phenomena,such as quantum optomechanical entanglement,quantum coherence of mechanical oscillator and ground-state cooling of mechanical motion mode,have been studied in detail.At the same time,the cavity optomechanical system is also used to explore the transformation of mechanical motion mode from classical property to the quantum region.It is noted that the mechanical oscillator is always coupled with the dissipative environment,which makes the study of energy flow from the thermal environment of the mechanical oscillator to the coupled cavity optomechanical system also of great significance.Based on the proposed two kinds of hybrid cavity optomechanical systems,this paper studies the steady-state thermophonon flux from the ambient heat source to the coupling system.Furthermore,we explore the relationship between the ground-state cooling of mechanical oscillator motion mode and the characteristics of thermophonon flux.The paper mainly includes the following two parts:In the first part,the steady-state thermophonon flux is studied in a double-cavity optomechanical system.The system consists of two optical cavities and a mechanical oscillator.In the research,we find that the direction and magnitude of the thermophonon flux in the system can be controlled flexibly by coupling an active cavity with gain to the passive cavity.In particular,the injected squeezing vacuum can reverse the nonequilibrium characteristics of the system and change the thermophonon flux from positive to negative.We also investigate in detail the influence of the driving power and the photon tunneling strength on the flux,which can widen the energy transfer channel of the system.In the second part,the steady-state thermophonon flux and ground-state cooling characteristics are studied in the cavity optomechanical system including degenerate optical parametric amplifier and atomic quantum vacuum force.The system consists of a suspended graphene sheet,a single atom,a degenerate optical parameter amplifier and an optical cavity.The degenerate optical parametric amplifier can greatly enhance the nonlinear optical effect in the cavity optomechanical system.We found that the cooling characteristics of the graphene oscillator and the amplitude of the thermophonon flux can be flexibly controlled by changing the vacuum coupling strength between trapped atom and nearby graphene sheet.In addition,we also find that the maximum thermophonon flux always corresponds to the minimum effective phonon number of graphene sheet,which benefits from the optimal thermophonon transport of the system.These system optimization characteristics are helpful to the design of cavity optomechanical system and its application in quantum optics and quantum information.