Haixia Chen

Interactions of Airy beams, nonlinear accelerating beams, and induced solitons in Kerr and saturable nonlinear media

We investigate numerically interactions between two in-phase or out-of-phase Airy beams and nonlinear accelerating beams in Kerr and saturable nonlinear media in one transverse dimension. We discuss different cases in which the beams with different intensities are launched into the medium, but accelerate in opposite directions. Since both the Airy beams and nonlinear accelerating beams possess infinite oscillating tails, we discuss interactions between truncated beams, with finite energies. During interactions we see solitons and soliton pairs generated that are not accelerating. In general, the higher the intensities of interacting beams, the easier to form solitons; when the intensities are small enough, no solitons are generated. Upon adjusting the interval between the launched beams, their interaction exhibits different properties. If the interval is large relative to the width of the first lobes, the generated soliton pairs just propagate individually and do not interact much. However, if the interval is comparable to the widths of the maximum lobes, the pairs strongly interact and display varied behavior.

Surface solitons of four-wave mixing in an electromagnetically induced lattice

By creating lattice states with two-dimensional spatial periodic atomic coherence, we report an experimental demonstration of generating two-dimensional surface solitons of a four-wave mixing signal in an electromagnetically induced lattice composed of two electromagnetically induced gratings with different orientations in an atomic medium, each of which can support a one-dimensional surface soliton. The surface solitons can be well controlled by different experimental parameters, such as probe frequency, pump power, and beam incident angles, and can be affected by coherent induced defect states.

Parametric Amplification and Cascaded-Nonlinearity Processes in Common Atomic System

For the first time, we study the parametric amplification process of multi-wave mixing (PA-MWM) signal and cascaded-nonlinearity process (CNP) in sodium vapors both theoretically and experimentally, based on a conventional phase-conjugate MWM and a self-diffraction four-wave mixing (SD-FWM) processes, which are pumped by laser or amplified spontaneous emission (ASE), respectively. For laser pumping case, SD-FWM process serves as a quantum linear amplifier (a CNP) out (inside) of the resonant absorption region. While for ASE case, only the CNP occurs and the output linewidth is much narrower than that of the MWM signal due to the second selected effect of its electromagnetically induced transparency window. In addition, the phase-sensitive amplifying process seeded by two MWM processes is discussed for the first time. Theoretical fittings agree well with the experiment. The investigations have important potential applications in quantum communication.

Effect of annealing temperature on the morphology and piezoresponse characterisation of poly(vinylidene fluoride-trifluoroethylene) films via Scanning Probe Microscopy

Poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE (70/30)) films were synthesized on a gold/glass substrate via spin coating. The films were annealed at a temperature between and . Nanoscale characterisation of the morphology, polarization switching, and local piezoresponse hysteresis loops of PVDF-TrFE film was studied using a scanning probe microscope (SPM). Ferroelectric switchable domains were identified by piezoresponse force microscopy (PFM) for all films. Small grains, with weak piezoresponse character, were observed for films annealed just above the Curie temperature. Acicular grains were obtained when the annealing temperature approached the melting point and the piezoresponse increased. Annealing above the melting point decreased the piezoresponse and the morphology changed dramatically into plate-like structures.

Parametrically Amplified Bright-state Polariton of Four- and Six-wave Mixing in an Optical Ring Cavity

We report experimental studies of bright-state polaritons of four-wave mixing (FWM) and six-wave mixing (SWM) signals through cascade nonlinear optical parametric amplification processes in an atom-cavity composite system for the first time. Also, the coexisting cavity transmission modes of parametrically amplified FWM and SWM signals are observed. Finally, electromagnetically induced absorption by the FWM cavity modes in the probe beam is investigated. The investigations can find potential applications in multi-channel narrow-band long-distance quantum communication.

Nonlinear Talbot effect of rogue waves

Akhmediev and Kuznetsov-Ma breathers are rogue wave solutions of the nonlinear Schrödinger equation (NLSE). Talbot effect (TE) is an image recurrence phenomenon in the diffraction of light waves. We report the nonlinear TE of rogue waves in a cubic medium. It is different from the linear TE, in that the wave propagates in a NL medium and is an eigenmode of NLSE. Periodic rogue waves impinging on a NL medium exhibit recurrent behavior, but only at the TE length and at the half-TE length with a π-phase shift; the fractional TE is absent. The NL TE is the result of the NL interference of the lobes of rogue wave breathers. This interaction is related to the transverse period and intensity of breathers, in that the bigger the period and the higher the intensity, the shorter the TE length.

Observation of dressed odd-order multi-wave mixing in five-level atomic medium

By selectively blocking specific laser beams, we investigate coexisting seven distinguishable dressed odd-order multi-wave mixing (MWM) signals in a K-type five-level atomic system. We demonstrate that the enhancement and suppression of dressed four-wave mixing (FWM) signal can be directly detected by scanning the dressing field instead of the probe field. We also study the temporal and spatial interference between two FWM signals. Surprisingly, the pure-suppression of six-wave mixing signal has been shifted far away from resonance by atomic velocity component. Moreover, the interactions among six MWM signals have been studied.

Parametric amplification of dressed multi-wave mixing in an atomic ensemble

We theoretically investigate the influence of a dressing field on parametric amplification multi-wave mixing (PA-MWM) processes in an atomic ensemble for the first time. The quantum spatial properties of PA-MWM signals are demonstrated by studying the cone emissions. Meanwhile, we investigate the intensities, the intensity difference squeezing, and the intensity noise correlation of bright twin PA-MWM beams, which are generated by injecting the MWM signals into the input ports of a spontaneous parametric four-wave mixing process. Both the spatial properties and the quantum correlation can be enhanced or suppressed via a bright state or a dark state, which is induced by the single or double dressing effect. This study has potential applications in quantum security, quantum imaging and long distance quantum communications.

Phase control of bright and dark states in four-wave mixing and fluorescence channels

We first investigate the phase control of the switch between bright and dark states in the transmitted probe, four-wave mixing (FWM) and fluorescence signals in a four-level  85Rb atomic system. With the relative phase modulated from 0 to −π, pure dark state in the FWM and fluorescence channels can be switched to pure bright state, corresponding to the switch from electromagnetically induced transparency to electromagnetically induced absorption. Meanwhile, the results could be obtained in solid crystals. Such phase controlled switch could have potential applications in optical communication and quantum information processing.

Observation of Autler-Townes splitting in six-wave mixing

We report an observation of the self- and external-dressed Autler-Townes (AT) splitting in six-wave mixing (SWM) within an electromagnetically induce transparency window, which demonstrates the interaction between two coexisting SWM processes. The multi-dressed states induced by the nested interactions between many dressing fields and the five-level atomic system lead to the primary, secondary and triple AT splittings in the experiment. Such controlled multi-channel splitting of nonlinear optical signals can be used in a range of applications, e.g. the wavelength-demultiplexer in optical communication and quantum information processing.