Study On The Ground State Cooling And Optics Manipulation In Optomechanical Systems

Cavity optomechanics could be used to realize the precise optical manipulation of mechanical resonators and the regulation of light by mechanical resonators,and therefore,it provides a unique platform for a variety of applications,including preparation of nonclassical mechanical states,observation of the boundary between classical physics and quantum physics,precision measurement,sensitive sensing,and quantum information processing.Ground state cooling is key for these applications in cavity optomechanical systems,meanwhile the system regulation on optical effects,such as Kerr nonlinearity and induced transparency effects,is of great value in precision measurements and quantum optical information processing.This dissertation focus on the ground state cooling and the manipulation of optical filed in cavity optomechanical systems as follow:(1)It is very difficult to achieve ground state cooling through traditional resolved sideband cooling,because there is the strong optomechanical couplinglimit on a cavity optomechanical system consisting of a high quality optical cavity.We theoretically propose the two-level qubits assisted cavity optomechanical system,and there are the electromagnetically induced absorption(EIA)-like and normal mode splitting(NMS)effects formed by the interaction of qubits and the cavity field in the system proposed.The cooling effects with the two effects can break the limit of the strong optomechanical coupling to obtain a lower number of phonons than that of the resolved sideband cooling,and the former effect can achieve a better cooling effect with the weak qubits-cavity coupling strength than that of the latter effect under the same optomechanical coupling strength.In addition,the system can also achieve ground state cooling under unresolved sideband condition,and compared with the previous works under two-photon off-resonance condition the cooling effects of the system are similar without needing the very strong qubit-cavity coupling strength.(2)Although the strong optomechanical coupling limit can be broken by using the assistant of two-level qubits,the heating process caused by the quantum backaction still exists to limit the cooling effect for the mechanical resonator,namely the quantum backaction limit.We theoretically propose the three-level atomic ensemble cavity opmechanical system with AGR effect to improve the cooling effect and suppress the heating process.By analyzing the cooling dynamics,the results show that the system can form two effective coupling modes,and the corresponding driving field detuning for the maximum cooling rate can be given according to the effective coupling modes.The quantum interference between two effective coupling modes can be formed by the ARG effect,so that it can completely suppress the heating process to break through the quantum backaction limit.Furthermore,ground state cooling in this system can be still achieved under the unresolved sideband condition with the weak optomechanical strength.(3)We further studied the manipulation of optical nonlinear in the three-level atomic ensemble cavity optomechanical system,because nonlinear interactions of lights play an important role in quantum optical information processing.The results show that the third-order susceptibility of atoms in the system will produce two self-Kerr nonlinearity terms under the influence of cavity field fluctuation.The first self-Kerr nonlinearity term comes from the typical three-level EIT effect,and the second self-Kerr nonlinearity term is caused by the cavity field fluctuation,in which the second term value is 4 orders of magnitude larger than the first term under the large number of atoms.The self-Kerr nonlinearity of the system can be improved by enhancing the atom-cavity interaction and the optomechanical interaction.Futhermore,we can obtain a large photon-phonon cross-Kerr nonlinearity by adding an external mechanical driving field in the system,and the cross-Kerr nonlinearity value is respectively regulated by the atom-cavity coupling strength and the single photon optomechanical coupling strength,which may apply in measuring the phonon number of a mechanical resonator.The results in this work are expected to provide a new method to generate large Kerr nonlinearities.(4)Further considering the sideband effects,we study the induced transparency phenomena in a two-level QW-cavity optomechanical system with the anti-Stokes and Stokes sideband effects.Even if there is only one input light field,the system can also form the DEIT effect in the anti-Stokes sideband case.We use the dressed-state theory to explain it,and find that the double-dark resonances can be formed in the system under the optomechanical interaction assisted.Similarly,double-dark resonances can also be achieved in the Stokes sideband case,but the middle narrow peak appears as an absorption peak or a gain peak under different coupling strength conditions.For the middle narrow peaks,the influences of QW-cavity and optomechanical coupling strengths on them are competitive,so that the competitive relationship can lead to the generation of completely transparent window being useful for non-absorption optical propagation.Furthermore,we propose a mass sensing scheme with high resolution by using this system with the middle narrow peaks.