The Effect Of The Auxiliary Cavity On The Spectrum Of Fluctuation Of Cavity And Optical Power Spectrum In Cavity Optomechanical System

Cavity optomechanical system is a new system which is used to study the interaction between cavity and mechanical resonator.In the cavity optomechanical system,optical cavity will generate radiation pressure on the mechanical resonator,which leads to the mechanical resonator can be manipulated.In this thesis,we study the spectrum of fluctuation and the optical force spectrum formed by the radiation pressure exerted by the optical cavity on the resonator.Up to now,the spectrum of fluctuation and the optical force spectrum of the standard single-cavity optomechanical system have been studied by many scientists.We will discuss the standard single-cavity optical power system coupled with an assisted cavity,the changes of optical force spectrum can be explained by the spectrum of fluctuation of the optical cavity,and then interpreting cooling mechanism of mechanical resonator in different assisted cavity systems.First of all,when the assisted cavity is a passive cavity,the optomechanical system is under the unresolved-sideband limit.Firstly,when considering that the coupling between the two cavities is strong,according to the two-photon resonance phenomenon of the spectrum of fluctuation of optical cavity,the phenomenon interprets that the optical power spectrum splits to a valley when an auxiliary cavity is added in the optomechanical system at the two-photon resonance,the force of the optical cavity exerting on the mechanical resonator is weakened,and the energy of the mechanical resonator can be continuously transmitted to the optical cavity,then leaked out from the optical cavity to achieve the cooling the mechanical resonator.Secondly,when the assisted cavity is an active cavity,the optomechanical system is also under the unresolved-sideband limit.Firstly,when considering that the coupling between the two cavities is strong,observing the fluctuation of spectrum at the weak gain rate,due to the two-photon resonance,the spectrum line splits.When the gain rate is increased,the coupled active cavity enhances the anti-Stoke process,which can improve the cooling process and suppress the heating process in the optical power spectrum.Coupling an active cavity has a positive effect on the cooling the mechanical resonator.Finally,when the coupling between the two cavities is weak,regardless of whether the auxiliary cavity is a passive cavity or an active cavity,the double-cavity optomechanical system can be equivalent to a single-cavity optomechanical system,it is impossible to cool the mechanical resonator.