Experimental Study On Coherent Phonon Manipulation In Cavity Optomechanical System

Micro-nano mechanical resonators can interact with different physical systems to transfer various physical fields to the vibrations(phonons)of mechanical resonator.Control of phonon transport among mechanical modes allows for information exchange between different physical systems.In addition,the implementation of coherent phonon manipulation also provides the possibility of further observe quantum phenomena,such as superposition phonon state,at macroscale.Therefore,the study of coherent phonon manipulation in micro-and nano-mechanical systems is of great importance.With the recent advancing of micro-fabrication technology,the mechanical quality of mechanical resonators has been increased significantly so that the even weak interaction between optical field and mechanical oscillation can cause observable influence to the mechanical properties of mechanical resonators.In this dissertation,we carried out experimental studies on coherent phonon manipulation in a coupled-two-cantilever-based two-mode optomechanical system.Our experiment demonstrates that the classical two-mode optomechanical system is analogous to quantum two-level system.Special emphasis is placed on coherent phonon manipulation at strong driven condition using the well-developed protocols in quantum two-level systems.And coherent transfer of phonons between the coupled cantilevers is achieved using these protocols.The followings are the chief content of the dissertation:1.Tunable two-mode cavity optomechanical system.We construct a coupled-two-cantilever based membrane-in-the-middle cavity optomechanical system,in which strong dispersive optomechanical coupling can be obtained.The two cantilevers,which are elastically connected,are hybridized into two normal modes.By changing the optical trapping power,we can modify the distribution of normal modes between the cantilevers.Specifically,avoided crossing of the two normal modes is observed when the frequencies of the two cantilevers are identical.2.Optically mediated normal-mode splitting.The normal-mode splitting at weal driving condition is investigated in our tunable two-mode cavity optomechanical system.By changing the amplitude of driving field,we can control the parametric coupling strength of the two normal modes and hence phonon transferring between the two modes at different rates.3.Landau-Zener-like transition in the two-mode cavity optomechanical system.The Landau-Zener-like transition of phonon is studied in the two-mode system through changing speed at which the avoided-crossing point is traversed.When the avoided-crossing point is traversed for the second time,changing the evolution time between the two transitions results into the Stuckelberg interference of phonon.By using the Stiickelberg interferometry,the Stocks phase acquired each Landau-Zener transition is measured in the classical system for the first time.Then,multiple-passage Landau-Zener transition is studied under a strong periodic harmonic driving.Our experimental results show that phonons can be tightly bonded to the cantilevers at specific driving condition because of coherent destructive interference of phonon.By changing the cdriving condition,we implemented a coherent optomechanical switch capable of fully controlling the effective coupling strength at the avoided-crossing point.4.Geometric Stuckelberg interferometry of phonon.We construct a geometric Stuckelberg interferometry using two parametrically coupled mechanical modes.By adjusting the driving field so that its trajectory forms a close loop in parametric space.We show that evolution of the mechanical states between the two Landau-Zener transitions can adiabatically follows the change of the effective field on the Bloch sphere.The geometric phase acquired after a round-trip Landau-Zener transition can be controlled through changing solid angle enclosed by the evolution path on the Bloch sphere.To eliminate the dynamical phase accumulated during the evolution,the Hahn-echo technique is employed to achieve an all-geometric manipulation of phonon.Finally,the white noises are intentionally added into the driving field to study the noise induced decoherence in the dynamical and geometric interference.Our experiments show that the well-preserved coherence obtained in geometric interference indicates that the geometric phase is robust against certain noises.