Chen Xian-Feng

Second-harmonic generation with broadened flattop bandwidth in aperiodic domain-inverted gratings

We report on a theoretical analysis for the broadened bandwidth of the fundamental waves in aperiodic gratings. The sequences and the length of the domains are optimized to realize the pre-designed wide bandwidth in the quasi-phase-matched (QPM) second-harmonic generation (SHG) by the simulated annealing (SA) method. About 3 nm prescribed flattop bandwidth as the full width at 95% maximum with 25% reduction of the nonlinear coefficient relative to that of a perfectly periodic QPM grating are obtained. Domains overgrown owing to the room-temperature electric poling technique show little influence on the broad bandwidth of the fundamental waves.

Painleve Analysis and Some Solutions of (2 + 1)-Dimensional Generalized Burgers Equations

Burgers equation describes a lot of phenomena in physics fields, and it has attracted much attention. In this paper, the Burgers equation is generalized to (2+1) dimensions. By means of the Painleve analysis, the most generalized Painleve integrable (2+1)-dimensional integrable Burgers systems are obtained. Some exact solutions of the generalized Burgers system are obtained via variable separation approach.

Teleportation of an Arbitrary Three-Particle State via Three EPR Pairs

A scheme of teleportation of an arbitrary three-particle state is presented when three pairs of entangled particles are used as quantum channels. After the Bell state measurements are operated by the sender, the original state with deterministic probability can be reconstructed by the receiver when a corresponding unitary transformation is followed.

Dislocation behaviour during cyclic deformation of niobium single crystals

Abstract Dislocation structures formed during cyclic deformation of niobium single crystals have been studied. Single crystals of both [321] and [110] orientations have been cyclically deformed in tension-compression under strain control. Moreover, the mechanical property data are supplemented by the direct observation of dislocation arrangements by transmission electron microscopy. In the case of [321] orientation single crystals the hardening curve can be divided into three stages, i.e. first, rapid-hardening and saturation stages associated with various dislocation structures. In the first stage the dominan features of the dislocation configurations are high density networks and debris loops. In the rapid-hardening stage the main feature is the formation of dislocation bundles. In the saturation stage the characteristic features are the dislocation bundles and the screw dislocations between bundles. The imposed strain is accomodated mainly by the motion of screw dislocation travelling to and fro between the bundles. For the [110] orientation single crystals the hardening curves are similar to those of the [321] orientation except that dislocation bundles of more than one direction appear during the first few cycles. Three-dimensional cell, two-dimensional cell and bundle structures are summarized as the saturated dislocation structures of b.c.c. metals.

Homotopic mapping method of solitary wave solutions for generalized complex Burgers equation

A class of generalized complex Burgers equation is considered. First, a set of equations of the complex value functions are solved by using the homotopic mapping method. The approximate solution for the original generalized complex Burgers equation is obtained. This method can find the approximation of arbitrary order of precision simply and reliably.

Probabilistic Teleportation of a Three-Particle State

A scheme for teleporting a three-particle state is proposed when three pairs of entangled particles are used as quantum channels. Quantum teleportation can be successfully realized with a certain probability if the receiver adopts an appropriate unitary-reduction strategy. The probability of successful teleportation is determined by the smaller coefficients of the three entangled pairs.

Optimized Second Harmonic Generation of Femtosecond Pulse by Phase-Blanking Effect in Aperiodically Optical Superlattice

In order to minimize the effect of the unconsidered frequency components on the generated compression pulse, the phasing-blanking effect is taken into account of designing the one-dimensional aperiodic domain reversal structure. Hierarchic genetic algorithm for the design of a domain reversal grating to modulate the spectrum and phase of the generated SH pulse simultaneously are presented. Our simulation shows that the quality of an output pulse is fairly improved.

Electrical Properties of Nanostructured Magnetic Colloid and Influence of Magnetic Field

We investigate the electrical properties of the nanostructured magnetic colloid without and with magnetic field. The competition between the directional motion of the charged magnetic nanoparticles and other minor nonmagnetic impurities (also small amount of ions) under applied voltage and their random orientation due to thermal activation is implemented to elaborate the electrically conduction mechanism under zero magnetic field. Two equivalent electric circuits are employed for explaining the charging and discharging processes. The tunnelling conduction mechanism upon application of externally magnetic field may exist in the nanostructured magnetic colloid. The alternation of the two conduction mechanisms accounts for the current spikes when the magnetic field is switched on or off. This work presents the peculiar electrical phenomena of the magnetically colloidal system.

Evolution of Dark Spatial Soliton in Quasi-phase-matched Quadratic Media

We theoretically investigate the evolvement of dark spatial soliton with cascading quadratic nonlinearity in quasi-phase-matched second harmonic generation. It is shown that the dark solitary wave can propagate stably when background intensity is large enough, in which diffraction of beam can be balanced by the cascading quadratic nonlinearity. We also analyze the influence of phase-mismatch on the stability of dark soliton propagation.

Teleportation of a Three-Particle State via Entanglement Swapping

A scheme for teleporting a three-particle state is proposed when three pairs of entangled particles are used as quantum channel. After a sender operates the Bell-state measurement, the original state with deterministic probability can be reconstructed when the receiver performs a corresponding measurement with unitary transformation.