Nonreciprocal Phonon Laser And Optomechanically-induced Transparency In Spinning Devices

Remarkable advances have been witnessed in cavity optomechanics,based on the coherent interaction of light and mechanical motion,which has a variety of applications,such as highly sensitive sensors,quantum state transducers,coherent phonon lasing or transport,and optomechanically induced transparency(OMIT).In parallel with optomechanics,nonreciprocal devices allowing one-way transport of waves have attracted increasing attentions,which are widely used in modern measurement and communication systems.This thesis focuses on cavity optomechanics,in which phonon laser and OMIT in spinning systems are studied in detail,as well as superradiance-driven phonon laser.The main results are introduced briefly as follows.(1)Phonon laser is the coherent amplification of mechanical vibrations,which can be realized in a system consisting of two coupled whispering-gallery-mode microresonators.Nonreciprocal phonon lasing in a coupled cavity system is studied,which is composed of an optomechanical resonator and a spinning resonator.The optical Sagnac effect leads to significant modifications in both the mechanical gain and the power threshold for phonon lasing.More importantly,the phonon lasing in this system is unidirectional;that is,the phonon lasing occurs when the coupled system is driven in one direction but not the other.This work establishes the potential of spinning optomechanical devices for low-power mechanical isolation and unidirectional amplification.This provides a new route,well within the reach of current experimental abilities,to operate cavity optomechanical devices for a wide range of applications such as directional phonon switches,invisible sound sensing,and topological or chiral acoustics.(2)Superradiance is the collective coherent emission from ensembles of emitters,which can be realized by pumping a Bose-Einstein condensate trapped in an optical cavity.Superradiance-driven phonon laser is studied in this thesis.In the proposed scheme,the optomechanical cavity contains a movable membrane,which supports a mechanical mode,and the superradiance cavity can generate the coherent collective light emissions by applying a transverse pump to an ultracold intracavity atomic gas.The superradiant emission turns out to be capable of enhancing the phonon laser performance.This indicates a new way to operate a phonon laser with the assistance of coherent atomic gases trapped in a cavity or lattice potentials.(3)OMIT as an analog of electromagnetically induced transparency in atoms is a phenomenon resulting from destructive interferences of signal light in optomechanical systems.OMIT in a spinning Kerr-nonlinear resonator is studied.The propagation of the signal light,including the transmission rate and the group delay,are strongly affected by the Kerr nonlinearity and rotation-induced Sagnac effect,with a Fano-shape transmission spectrum.Nonreciprocal light propagation can be realized by tuning the rotation speed or the optical detuning.In particular,a symmetric transparency window appears by tuning the Sagnac shift to compensate the Kerr induced shift.Fast-to-slow light switch can also be achieved,providing a practical way to control light propagation in spinning nonlinear resonators.