Xiaoxue Yang

Giant Kerr nonlinearities and solitons in a crystal of molecular magnets

The authors show the formation of microwave solitons in a crystal of molecular magnets via an electromagnetically induced transparency and have the giant cross-phase modulation phase shifts with the advantages of low pump powers, low absorptions, high sensitivities, and certain frequency tunability.

Carrier-envelope phase-dependent effect of high-order sideband generation in ultrafast driven optomechanical system

We analyze the features of the output field of a generic optomechanical system that is driven by a control field and a nanosecond driven pulse, and find a robust high-order sideband generation in optomechanical systems. The typical spectral structure, plateau and cutoff, confirms the nonperturbative nature of the effect, which is similar to high-order harmonic generation in atoms or molecules. Based on the phenomenon, we show that the carrier-envelope phase of laser pulses that contain huge numbers of cycles can cause profound effects.

Theory of microcavity-enhanced Raman gain.

We present a method for obtaining a simple relation between bulk and cavity-modified Raman gains for microcavities with arbitrary geometric shapes. The analytical expression for the microcavity-enhanced Raman gain quantitatively accounts quite well for all the main features of the related experiments.

Ultraslow temporal vector optical solitons in a cold four-level tripod atomic system

We show the possibility of generating ultraslow temporal vector optical solitons in a cold lifetime-broadened four-level tripod atomic medium under Raman excitation. We demonstrate that the two orthogonally polarized components of the low-intensity signal field can evolve into various distortion-free temporal vector optical solitons, such as bright-bright vector solitons with ultraslow group velocity. These results are produced from the balance of self- and cross-phase modulation effects and dispersion. We also show that Manakov temporal vector solitons may be realized by adjusting the corresponding self- and cross-phase modulation and dispersion effects of our system.

Exact eigenstates for a class of models describing two-mode multiphoton processes

We present an efficient approach to studying the spectra and eigenstates for nonlinear models describing multiphoton processes. We obtain the exact explicit analytical expressions of all the energy spectra and eigenstates in terms of a parameter for a class of models describing two-mode multiphoton processes. The parameter is shown to be determined by the roots of a simple polynomial.

Asymmetric optical transmission in an optomechanical array

Optical cavity combining a mechanical degree of freedom provides a unique platform to implement information transmission and processing via optomechanical effects, and introduces a strong link between nanophotonics and nanomechanics. Here, we study the optical property of a cascaded optomechanical array, which consists of two or more optomechanical systems. We find that the steady states of the optomechanical array have algebraic duality symmetry for the case of two identical optomechanical resonators, which is exactly the embodiment of the spatial symmetry and leads to symmetric optical transmission. Breaking of the algebraic duality symmetry gives rise to different behaviors between the forward and the backward transmission, which can be remarkable under low input power. Our results may have potential application for achieving high precision measurement and on-chip manipulation of light propagation.

Carrier-envelope-phase dependent coherence in double quantum wells

By analyzing the interaction of a few-cycle laser pulse within an asymmetric semiconductor double quantum well structure, we show that the transient coherence thus produced is strongly dependent on the carrier-envelope-phase (CEP) and significantly enhanced due to the Fano-type interference. A method to determine the CEP is proposed by directly mapping the CEP dependent coherence to the quantum beat signals.

N-qubitW state of spatially separated single molecule magnets.

A simple scheme is proposed to generate a N-qubit W state of spatiall separated single molecule magnets (SMM) in a cavity-fiber-cavity system. In the present scheme, the framework consisting of entangled qubits can be expediently designed according to our needs. By quantitatively discussing the case of N=4, we show that the effects of SMMs spontaneous decay and photon leakage out of fiber can be suppressed in our scheme due to the presence of virtual excited processes in SMM and fiber modes. Moreover, we also show that the present scheme is robust with respect to some deviations of experimental parameters, and as a result, the present investigation provides a research clue for realizing multi-partite entanglement between distant SMMs solid-state nanostructures, which may result in a substantial impact on the progress of multi-node quantum information network.

Iterative ghost imaging.

The recovered image in ghost imaging (GI) contains an error term when the number of measurements M is limited. By iteratively calculating the high-order error term, the iterative ghost imaging (IGI) approach reconstructs a better image, compared to one recovered using a traditional GI approach, without adding complexity. We first propose an experimental scheme, for which IGI can be realized, namely the narrowed point spread function and exponentially increased signal-to-noise ratio (SNR) are realized. The exponentially increasing SNR when implementing IGI results from the replacement of M with M(k). Thus, a perfect recovery of the unknown object is demonstrated with M slightly bigger than the number of speckles in a typical light field. Based on our theoretical framework from the angle of high-order correlation R(k), the two critical behaviors of the iterative coefficients α and the measurements M are derived and well explained.

Tunable slow light in a quadratically coupled optomechanical system

We theoretically investigate the slow light in a quadratically coupled optomechanical system. Different from the linear coupling case, the slow light via quadratic coupling derives from a two-phonon process, and the fluctuation in displacement plays a vital role in nonlinear coherence. The numerical results show that the slow light can be realized in an extensive range of parameters even at high temperature, e.g., 200 K. We also find that the environment temperature which provides almost all of the phonon energy, together with the coupling field power, jointly drive the realization of slow light.