Zhi-Ming Zhang

Tunable double optomechanically induced transparency in an optomechanical system

We study the dynamics of a driven optomechanical cavity coupled to a charged nanomechanical resonator via Coulomb interaction, in which the tunable double optomechanically induced transparency (OMIT) can be observed from the output field at the probe frequency by controlling the strength of the Coulomb interaction. We calculate the splitting of the two transparency windows, which varies near linearly with the Coulomb coupling strength in a robust way against the cavity decay. Our double-OMIT is much different from the previously mentioned double-EIT or double-OMIT, and might be applied to measure the Coulomb coupling strength.

Triple-wavelength switchable Erbium-doped fiber laser with cascaded asymmetric exposure long-period fiber gratings

The cascaded asymmetric exposure long-period fiber gratings are fabricated by CO(2) laser, which provide multi-wavelength filters with anisotropic transmission spectrum under different states of polarization. Inserting this device in the ring cavity of an erbium-doped fiber laser, a triple-wavelength switchable lasing laser with equal spacing of 2.6 nm has been obtained. Owing to the polarization dependent loss of the new cascaded long-period fiber grating, the wavelength switching of random combination of C(1) (3), C (2) (3), and C(3) (3) is demonstrated through the polarization controlling. We derive the wavelength switch to the polarization characteristic of cascaded asymmetric exposure long-period fiber gratings.

Defect solitons in parity-time symmetric superlattices.

We study defect solitons (DSs) in a parity-time (PT) symmetric superlattice with focusing Kerr nonlinearity. The properties of the DSs with a PT symmetrical potential are obviously different from those in a superlattice with a real refractive index. Unusual features stemming from PT symmetry can be found. Research results show that the solitons with a zero defect or a positive defect can exist and stably propagate in the semi-infinite gap, but they cannot exist in the first gap. For the case of a negative defect, the soliton can stably exist in both the semi-infinite gap and the first gap.

Tunable multi-channel inverse optomechanically induced transparency and its applications

In contrast to the optomechanically induced transparency (OMIT) defined conventionally, the inverse OMIT behaves as coherent absorption of the input lights in the optomechanical systems. We characterize a feasible inverse OMIT in a multi-channel fashion with a double-sided optomechanical cavity system coupled to a nearby charged nanomechanical resonator via Coulomb interaction, where two counter-propagating probe lights can be absorbed via one of the channels or even via three channels simultaneously with the assistance of a strong pump light. Under realistic conditions, we demonstrate the experimental feasibility of our model by considering two slightly different nanomechanical resonators and the possibility of detecting the energy dissipation of the system. In particular, we find that our model turns to be a unilateral inverse OMIT once the two probe lights are different with a relative phase, and in this case the relative phase can be detected precisely.

Surface line defect solitons in square optical lattice.

We study the surface line defect gap solitons (SLDGSs) in an interface between a line defect of two-dimensional (2D) square optical lattice and the uniform media with focusing saturable nonlinearity. Some unique properties are revealed that the surface line defect of square optical lattice can profoundly affect the shape and stability of soliton. Stable soltion for the case of negative defect can exist in both of the semi-infinite gap and the first gap; unlike in the square lattice without defect, soliton can only exist in the semi-infinite gap. For the case of the positive defect, the solitons exist in the semi-inifite gap and stably exist in the low power region.

Controllable optomechanically induced transparency and ponderomotive squeezing in an optomechanical system assisted by an atomic ensemble

We propose a system for realizing controllable optomechanically induced transparency (OMIT) and ponderomotive squeezing. In this system, an atomic ensemble driven by an external optical field couples with the cavity field in a typical optomechanical cavity. When the cavity is driven by a coupling laser and a probe laser, we can produce a switch for the probe field and adjust the width of the transparency window flexibly by manipulating the coupling strength between the atomic ensemble and the external optical field. We also investigate the ponderomotive squeezing properties of the transmitted field by analyzing its spectrum. Interestingly, the coupling strength between the atomic ensemble and the cavity field plays an important role in controlling the squeezing properties and the squeezing spectrum presents distinct features at red-detuned and blue-detuned frequencies by adjusting the coupling strength.

Microwave field controlled slow and fast light with a coupled system consisting of a nanomechanical resonator and a Cooper-pair box

We theoretically demonstrate an efficient method to control slow and fast light in microwave regime with a coupled system consisting of a nanomechanical resonator (NR) and a superconducting Cooper-pair box (CPB). Using the pump-probe technique, we find that both slow and fast light effects of the probe field can appear in this coupled system. Furthermore, we show that a tunable switch from slow light to fast light can be achieved by only adjusting the pump-CPB detuning from the NR frequency to zero. Our coupled system may have potential applications, for example, in optical communication, microwave photonics, and nonlinear optics.

Stationary entanglement between two nanomechanical oscillators induced by Coulomb interaction

We propose a scheme for entangling two nanomechanical oscillators by Coulomb interaction in an optomechanical system. We find that the steady-state entanglement of two charged nanomechanical oscillators can be obtained when the coupling between them is stronger than a critical value which relies on the detuning. Remarkably, the degree of entanglement can be controlled by the Coulomb interaction and the frequencies of the two charged oscillators.

Entangling cavity optomechanical systems via a flying atom

We propose a novel scheme to generate the entanglement between two cavity optomechanical systems (COMSs) via a flying two-level atom. We derive the analytical expressions for the generated entangled states. We find that there exist two processes for generating entanglement: one is the entanglement transfer between the two phonon-modes, and the other is the entanglement swapping-like process among the two photon-modes and the two phonon-modes. We analyze these two kinds of phenomena, respectively, by adjusting the distance between the two COMSs. Then we discuss the verification of the generated entangled states of the two COMSs, and analyze the decoherence of the generated entangled states. Finally, we discuss the experimental feasibility of our proposal.

Mechanical squeezing and photonic anti-bunching in a coupled two-cavity optomechanical system

We propose a scheme for generating the squeezing of a mechanical mode and the anti-bunching of photonic modes in an optomechanical system. In this system, there are two photonic modes (the left cavity-mode and the right cavity-mode) and one mechanical mode. Both the left cavity-mode and the right cavity-mode are driven by two lasers, respectively. The power of the driving lasers and the detuning between them play a key role in generating squeezing of the mechanical mode. We find that the squeezing of the mechanical mode can be achieved even at a high temperature by increasing the power of the driving lasers. We also find that the cavity-modes can show photonic anti-bunching under suitable conditions.