Theoretical Studies On The Dynamics Of Photon-Phonon/Magnon In PT-Symmetric Systems

Symmetry is one of the most important fundamental concepts in physics,and the studies about the PT-symmetric optical systems have emerged as an important new frontier in many fields,such as quantum optics and nonlinear optics,and have achieved many exciting developments.In recent years,with the development of optical microcavity structures,especially cavity optomechanical systems,PT-symmetric microcavity systems have been experimentally realized and have exhibited great potential for achieving distinctive optical behaviours which are unattainable with ordinary optical systems.The fundamental difference between the PT-symmetric structures and the traditional structure is that it has optical gain,which can be used to compensate the dissipation of the system,and can improve the quality factor of the cavity,so that the coupling strength between the microcavity and the microcavity,atomic,mechanical oscillator and magnon can be effectively enhanced.By studying the influence of different PT-symmetric structures on optical transmission characteristics,we can not only deepen the understanding of the PT symmetry theory,but also promote the application of PT-symmetric optical devices in precision measurement and optical communication.We discussed the dynamical properties of photon,phonon and magnon as well as its application in optical information transfer process in PT-symmetric optical systems.Including:First,we introduce the polarization freedom of the light field into the PTsymmetric optomechanical systems and study the phonon laser action,we find that the different nonlinear optomechanical interactions will occur when the system is pumped by different linearly polarized light fields through theoretical calculation,thus the intensity and threshold of the phonon laser action can be continuously adjusted by only tuning the photon polarization,which provides a new degree of freedom to realize phonon laser regulation.In addition,we find that there is a specific region for the optimum mechanical gain appearing in parameter areas of the cavity gain and loss.Finally,we propose to show the ability to coherently convert optical polarization information into the amplitude information of phonon by vector PT-symmetric optomechanical systems.Polarization is one of the basic characteristics of light,and the polarization-dependent peculiarity can inspire the exploration of the engineering of new polarization-related phonon laser devices and the photon-phonon converter.Second,we propose a PT-symmetric cavity-magnon system consisting of active cavity mode strongly interacting with magnon to study magnon-induced transparency(MIT)and amplification(MIA)by exploiting recent microwave-cavity-engineered ferromagnetic magnons.We find that due to the gain-induced enhancement of coherent coupling between the cavity field and the magnon,the transmitted probe power is remarkably enhanced about four orders of magnitude and the bandwidth also becomes much narrower,compared to passive cavity system.More importantly,the light transmission can be well controlled by adjusting the applied magnetic field without changing other parameters,and a Lorentzian-like spectra can be established between the transmitted probe power and the external magnetic field,which provides an additional degree of freedom to realize the coherent manipulation of optical transparency and amplification.Our results may offer an approach to make a low-power magnetic-field-controlled optical amplifier in PT-symmetric cavity-magnon system,and the magnetic-field-controlled characteristic can be applied to the optical communication.Third,we propose an active cavity-magnon system to study the chaotic dynamics of magnon induced by the intrinsic magnon Kerr nonlinearity.With the experimental attainable parameters,it is clearly shown that our regime enables switching from regular to chaotic motion and vice versa as well as regulating the lifetime of the transient chaos just by tuning the external magnetic field,which is ascribed to the magnetic-field-controlled magnonical nonlinearity.This investigation offers insight into the underlying physical process of nonlinear magnonics dynamics.Especially,our results pave a path toward exploring magnetic-field-controlled chaos and may find potential applications in secret communication.Fourth,we propose a new scheme of investigating the mechanical-EP-induced transparency and tunable fast-to-slow light phenomena in an optomechanical system which consists of an optical cavity and PT-symmetric mechanical resonators.We find that the transmission of the probe field changes from single to double transparency window via the transition from a broken mechanical PT-symmetric phase to an unbroken mechanical PT-symmetric phase due to the splitting of mechanical modes.And the efficiency of transparency can be significantly enhanced about three orders of magnitude in the vicinity of the mechanical EP,compared to passive mechanical resonators system.In addition,the mechanical EP can not only amplify the group delay,but also manipulate the switch from slow light to fast light.The robustness of group delay for loss and the requirement of low power make the mechanical-EP-controlled slow and fast light effect significant as a new path towards solving the switching problems in all-optical fiber communication networks engineering and information processing.Our scheme use PT-symmetric mechanical structures to manipulate optical information transmission,which may inspire the exploration of mechanical EP and the engineering of novel PT-symmetric devices.