[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

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Nature in London

A mechanism for asymmetric transport which is based on parity-time-symmetric nonlinearities is presented. We show that in contrast to the case of conservative nonlinearities, an increase of the complementary conductance strength leads to a simultaneous increase of asymmetry and transmittance intensity. We experimentally demonstrate the phenomenon using a pair of coupled Van der Pol oscillators as a reference system, each with complementary anharmonic gain and loss conductances, connected to transmission lines. An equivalent optical setup is also proposed.

/pdf/observation-of-asymmetric-transport-in-structures-with-4ijqeqnibr.pdf

Observation of Asymmetric Transport in Structures with Active Nonlinearities

Over recent years it has become experimentally possible to study the coupling of optical and mechanical modes by means of cavity-enhanced radiation pressure[1] which might enable ground state-cooling of macroscopic mechanical oscillators. For achieving this major goal in the field of cavity-optomechanics and for applications such as low-loss, narrowband ‘photonic clocks’ a combination of high optical finesse and high mechanical quality factors at mechanical oscillation frequencies exceeding the optical cavity's linewidth[1] is desirable. It has, however, so far not been possible to combine mechanical Q-factors comparable to those achieved in the field of nano- and microelectromechanical systems (e.g. [2]) with state-of-the-art values of optical finesse[3]. Here we show independent control over both optical and mechanical degrees of freedom in the same microscale optomechanical resonator[4].

Ultralow dissipation optomechanical resonators on a chip

Non-reciprocal devices, which allow the non-reciprocal signal routing, serve as the fundamental elements in photonic and microwave circuits and are crucial in both classical and quantum information processing. The radiation-pressure-induced coupling between light and mechanical motion in traveling wave resonators has been exploited to break the Lorentz reciprocity, realizing non-reciprocal devices without magnetic materials. Here, we experimentally demonstrate a reconfigurable nonreciprocal device with alternative functions of either a circulator or a directional amplifier via the optomechanically induced coherent photon-phonon conversion or gain. The demonstrated device exhibits considerable flexibility and offers exciting opportunities for combining reconfigurability, non-reciprocity and active properties in single photonic structures, which can also be generalized to microwave as well as acoustic circuits.

/pdf/reconfigurable-optomechanical-circulator-and-directional-299hyvruvo.pdf

Reconfigurable optomechanical circulator and directional amplifier

Many works are based on the steady-state analysis of mean-value dynamics in electro- or optomechanical systems to explore vibration cooling, squeezing, and quantum-state controlling of massive objects. These studies are always conducted in a red-detuned pumping field under a lower power to maintain a stable situation. In this paper we consider self-sustained oscillations of a cavity-field-driven oscillator combined with quadratic coupling in a blue-detuned regime above a pumping threshold. Our study finds that the oscillator will be far away from its steady-state behavior by conducting a self-sustained oscillation with a discrete amplitude locking effect producing a rich energy-balanced structure. The dynamical backaction of this self-oscillation on the field mode induces a multipeak field spectrum, which implies an efficient harmonic generation with its intensity modified not only by the displacement ${x}_{0}$ but also by the amplitude $A$ of the mechanical oscillation. The corresponding nonlinear field spectrum and its magnitude are analytically analyzed with quadratic coupling when the mechanical oscillator is dynamically locked to a self-sustained oscillation.

Self-sustained oscillation and harmonic generation in optomechanical systems with quadratic couplings

We propose a spinning nonlinear resonator as an experimentally accessible platform to achieve nonreciprocal control of optical solitons. Nonreciprocity here results from the relativistic Sagnac-Fizeau optical drag effect, which is different for pump fields propagating in the spinning direction or in the direction opposite to it. We show that in a spinning Kerr resonator, different soliton states appear for the input fields in different directions. These nonreciprocal solitons are more stable against losses induced by intermodal coupling between clockwise and counterclockwise modes of the resonator. Our work builds a bridge between nonreciprocal physics and soliton science, providing a promising route towards achieving soliton-wave optical isolators and one-way soliton communications.

Nonreciprocal optical solitons in a spinning Kerr resonator

A direct photon–phonon parametric effect of quadratic coupling on the mean-field dynamics of an optomechanical resonator in the large-scale-movement regime is found and investigated. Under a weak pumping power, the mechanical resonator damps to a steady state with a nonlinear static response sensitively modified by the quadratic coupling. When the driving power increases beyond the static energy balance, the steady states lose their stabilities via Hopf bifurcations, and the resonator produces stable self-sustained oscillation (limit-circle behavior) of discrete energies with step-like amplitudes due to the parametric effect of quadratic coupling, which can be understood roughly by the power balance between gain and loss on the resonator. A further increase in the pumping power can induce a chaotic dynamic of the resonator via a typical routine of period-doubling bifurcation, but which can be stabilized by the parametric effect through an inversion-bifurcation process back to the limit-circle states. The bifurcation-to-inverse-bifurcation transitions are numerically verified by the maximal Lyapunov exponents of the dynamics, which indicate an efficient way of suppressing the chaotic behavior of the optomechanical resonator by quadratic coupling. Furthermore, the parametric effect of quadratic coupling on the dynamic transitions of an optomechanical resonator can be conveniently detected or traced by the output power spectrum of the cavity field.

https://iopscience.iop.org/article/10.1088/1361-6455/aa74a0/pdf

Photon-phonon parametric oscillation induced by quadratic coupling in an optomechanical resonator

Lie transformation method on quantum state evolution of a general time-dependent driven and damped parametric oscillator

A direct photon-phonon parametric effect of the quadratic coupling on the mean-field dynamics of an optomechanical resonator in the large-scale-movement regime is found and investigated. Under a weak pumping power, the mechanical resonator damps to steady state with a nonlinear static response sensitively modified by the quadratic coupling. When the driving powerincreases beyond the static energy balance, the steady states lose their stabilities via Hopf bifurcations and the resonator produces stable self-sustained oscillation(limit-circle behavior) of discrete energies with step-like amplitudes due to the parametric effect of the quadratic coupling, which can be understood roughly by the power balance between gain and loss on the resonator. A further increase of the pumping power can induce chaotic dynamic of the resonator via a typical routine of period-doubling bifurcation but which can be stabilized by the parametric effect through an inversion bifurcation process back to limit-circle states. The bifurcation-to-inverse-bifurcation transitions are numerically verified by the maximal Lyapunov exponents of the dynamics and which indicate an efficient way to suppress the chaotic behavior of the optomechanical resonator by the quadratic coupling. Furthermore, the parametric effect of the quadratic coupling on the dynamic transitions of an optomechanical resonator can be conveniently detected or traced by the output power spectrum of the cavity field.

Lin Zhang

Papers

Self-sustained oscillation and harmonic generation in optomechanical systems with quadratic couplings

Nonreciprocal optical solitons in a spinning Kerr resonator

Photon-phonon parametric oscillation induced by quadratic coupling in an optomechanical resonator

Lie transformation method on quantum state evolution of a general time-dependent driven and damped parametric oscillator

Photon-phonon parametric oscillation induced by the quadratic coupling in an optomechanical resonator