All-optical Control Of Mechanical Oscillator Based On Cavity Optomechanics

This dissertation presents the study of all-optical control of the mechanical oscillator trapping potential based on the cavity optomechanics.It is well known that whispering gallery microcavities are significant and commonly used platforms for confining and storing light in small volume and for a relatively long period.In a micro scale whispering gallery mode(WGM)optical cavity,such as silica microtoroids,microspheres,microbottles or microrings,high optical quality factor(high-Q)together with small mode volume results in a large circulating optical power,and enable the study of a large variety of nonlinear and quantum optical phenomena at relatively low input power.Cavity optomechanics explores the interaction between optical modes in the microcavity and the nano/micromechanical motion.Optomechanical system provides an interface between the optical field and mechanical motion,which could be further applied for nanophotonic devices.Optomechanical system is a well-performed platform of coupling optical and acoustic degree of freedom and various applications have been realized using the optomechanics in dielectric microcavities including optomechanically induced transparency(OMIT),chaos transfer,gravitational wave detection,mass and force sensing and so on.In the 1970s,the fact that using focused laser beams could realize the trapping and controlling of nano-particles,and optical tweezers technology has been studying comprehensively since then.Inspired by this technology,in this dissertation,the "optical spring" effect of steady state light field of mechanical mode is studied which is based on the optomechanical effect of the photonics molecule consists of edge coupled whispering-gallery mode microcavities under the parity-time-symmetric condition.The edge coupled whispering-gallery mode microcavities are coupled to two waveguides and form the add drop structure.As the mechanical potential is important to reveal the nonlinear behavior of optomechanical modes,it is found that there is a special potential energy curve for mechanical modes under electromagnetic modulation with nonlinear coupling.The double-well trapping potential and a localized semi-square potential barrier can be engineered through modulating the properties of the electromagnetic field,including the cavity decay rate,detuning and pump power.Moreover,we investigate the conversion process of the system between different trapping potential modes and find that the conversion process takes at most 7?s.That is,the conversion speed between different potential modes can reach the MHz level.The engineered mechanical trapping potential and the highly efficient conversion between them pave the way to further study on the realization of novel quantum phononic devices such as phononic quantum switch and phononic quantum gate.