Recently, cavity optomechanics has become a rapidly developing research field exploring the coupling between the optical field and mechanical oscillation. Cavity optomechanical systems were predicted to exhibit rich and nontrivial effects due to the nonlinear optomechanical interaction. However, most progress during the past years have focused on the linearization of the optomechanical interaction, which ignored the intrinsic nonlinear nature of the optomechanical coupling. Exploring nonlinear optomechanical interaction is of growing interest in both classical and quantum mechanisms, and nonlinear optomechanical interaction has emerged as an important new frontier in cavity optomechanics. It enables many applications ranging from single-photon sources to generation of nonclassical states. Here, we give a brief review of these developments and discuss some of the current challenges in this field.

Review of cavity optomechanics in the weak-coupling regime: from linearization to intrinsic nonlinear interactions

In a GaAs quantum well waveguide coupled by orthogonally polarized optical fields, the influence of spin coherence on the optical bistability (OB) and multistability is investigated. It is shown that OB and multistability are very sensitive to the relative phase between applied fields.

Phase control of optical bistability and multistability via spin coherence in a quantum well waveguide

With the increase of communication frequency, terahertz (THz) communication technology has been an important research field; particularly the terahertz modulator is becoming one of the core devices in THz communication system. The modulation performance of a THz communication system depends on the characterization of THz modulator. THz modulators based on different principles and materials have been studied and developed. However, they are still on the way to practical application due to low modulation speed, narrow bandwidth, and insufficient modulation depth. Therefore, we review the research progress of THz modulator in recent years and evaluate devices critically and comprehensively. We focus on the working principles such as electric, optical, optoelectrical, thermal, magnetic, programmable metamaterials and nonlinear modulation methods for THz wave with semiconductors, metamaterials, and 2D materials (such as graphene, molybdenum disulfide, and tungsten disulfide). Furthermore, we propose a guiding rule to select appropriate materials and modulation methods for specific applications in THz communication.

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Modulators for Terahertz Communication: The Current State of the Art.

The generation of dark solitons in Bose-Einstein condensates with phase imprinting is studied by mapping it into the classic problem of a damped driven pendulum. We provide a simple but powerful scheme, designing the phase imprint for various desired outcomes of soliton generation. For a given phase step, we derive a formula for the number of dark solitons traveling in each direction, and examine the physics behind the generation of counterpropagating dark solitons.

Controlled Generation of Dark Solitons with Phase Imprinting

We study linear and nonlinear propagations of probe and signal pulses in a multiple quantum-well structure with a four-level, double Λ-type configuration. We show that slow, mutually matched group velocities and giant Kerr nonlinearity of the probe and the signal pulses may be achieved with nearly vanishing optical absorption. Based on these properties we demonstrate that two-qubit quantum polarization phase gates can be constructed and highly entangled photon pairs may be produced. In addition, we show that coupled slow-light soliton pairs with very low generation power can be realized in the system.

Giant kerr nonlinearity, controlled entangled photons and polarization phase gates in coupled quantum-well structures.

Optical bistability in a triple semiconductor quantum well structure with tunnelling-induced interference

In this article, a theoretical scheme is proposed to investigate the formation and propagation of three-wave coupled vector optical solitons with ultraslow group velocities in a lifetime-broadened seven-state triple-$\ensuremath{\Lambda}$ atomic system under Raman excitation. We show that in the presence of a weak applied magnetic field that removes the degeneracy of the corresponding sublevels of the atomic medium, three continuous-wave control fields with circularly left or right polarized fields induce a quantum interference effect which can largely suppress the absorption of the three low-intensity pulsed fields, that is, the circularly ${\ensuremath{\sigma}}^{\ensuremath{-}}$ (right), the linearly $\ensuremath{\pi}$, and the circularly ${\ensuremath{\sigma}}^{+}$ (left) polarized fields converted from one weak linear-polarized probe field. By means of the standard method of multiple scales, we solve the equations of motion of atomic response and probe-control electromagnetic fields and derive three-coupled nonlinear Schr\"odinger equations that govern the nonlinear evolution of the envelopes of the probe fields in this scheme. We then demonstrate that because of the nonlinear coupling to one another, the three probe fields can evolve into three-wave temporal, group velocity, and amplitude-matched optical solitons under appropriate conditions, which are produced from the delicate balance of the dispersion effects and the self- and cross-phase modulation effects. This scheme may thus pave the way to generate ultraslow vector optical solitons composed of three field components in a highly resonant atomic medium and result in a substantial impact on this field of nonlinear optics.

Formation and propagation of ultraslow three-wave-vector optical solitons in a cold seven-level triple- Λ atomic system under Raman excitation

We propose two schemes for deterministically generating three-partite Greenberger-Horne-Zeilinger (GHZ) and $W$ states of distant atoms based on the selective photon emission and absorption processes. In our schemes, it is found that the effects of atomic spontaneous decay and photon leakage out of fiber are suppressed effectively due to the presences of dispersive atom-field interaction and strong cavity-fiber coupling intensity. To check the experimental feasibility of our schemes, we also numerically simulated the effects of photon leakage out of the cavities, and the numerical simulation shows that our proposal is good enough to demonstrate the generation of three-partite GHZ and $W$ states of distant atoms with high fidelity. In addition, the present schemes can also be generalized to prepare N-partite $W$ state of distant atoms.

Xiangying Hao

Papers

Optical bistability in a triple semiconductor quantum well structure with tunnelling-induced interference

Formation and propagation of ultraslow three-wave-vector optical solitons in a cold seven-level triple- Λ atomic system under Raman excitation

Achieving multipartite entanglement of distant atoms through selective photon emission and absorption processes

Mid-infrared efficient generation by resonant four-wave mixing in a three-coupled-quantum-well nanostructure

Efficient four-wave mixing of a coupled double quantum-well nanostructure