Zhou Zhong-Xiang

Bright-dark incoherently coupled photovoltaic soliton pair

The coupling between two mutually incoherent optical beams that propagate collinearly in open-circuit photovoltaic photorefractive media is investigated. It is shown that an incoherently coupled bright–dark spatial soliton pair can be formed due to photovoltaic effect. The physical properties of such a soliton pair are also discussed.

Relativistic Magnetosonic Solitary Wave in Magnetized Multi-Ion Plasma

In the presence of an applied uniform magnetic field B0, the properties of 2-dimensional (2D) magnetosonic solitary waves of relativistic amplitude in the plasma containing electron, light ions He+, and heavy ions O+ are presented. In the weakly relativistic limit, a Kadomtsev–Petviashvili (KP) equation is derived by reductive perturbation method. We give the N-soliton solution of the KP equation and find dromion solutions of a potential of the physical field. The interaction law of the dromions is obtained, which shows there is no exchange of energy, momentum, and angular momentum before and after interaction of the dromions except for phase shifts.

Upconversion Emission Properties of Erbium- and Ytterbium-Doped Potassium Lithium Tantalate Niobate Ceramics

We investigate the luminescence properties of erbium-doped and erbium-ytterbium-codoped potassium lithium tantalate niobate ceramics prepared by the solid phase syntheses method. The crystalline structure and surface morphology of these ceramics are tested by x-ray diffraction and scanning electron microscopy. The green, red, and near-infrared upconversion photoluminescence properties are analyzed by the steady-state spectra under 975 nm and 800 nm excitations. These ceramics are well sintered and tetragonal tungsten type crystalline structure with the 4mm point group and the P4bm space group. The Er3+ upconversion emission integrated intensities increase with the increase in Er3+ ion concentration, while the green emission decreases with the increase in Yb3+ ion concentration under the 800 nm excitation. An effective energy back transfer process from the Er3+ 4S3/2 state to Yb3+ ground state plays an important role in enhancing the red emission and weakening the green emission.

Grey－grey incoherently coupled spatial soliton pairs in guest－host photorefractive polymers

We show that incoherently coupled grey–grey spatial soliton pairs can be established in guest–host photorefractive polymers under steady-state conditions, provided that their carrier beams have the same polarization, wavelength and are mutually incoherent. The properties of these soliton pairs, such as their width and polarization, are discussed in detail.

Structural, Electronic and Optical Properties of KTa0.5Nb0.5O3 Surface: A First-Principles Study

The crystal surface properties of potassium tantalite niobate, KTa0.5Nb0.5O3 (KTN), are studied with first-principles calculation based on the density functional theory (DFT). Generalized gradient approximation (GGA) functional analysis is also employed by using CASTEP software. The explanations for the differences of the ferroelectric and piezoelectric properties between the bulk and surface of the material are provided. The DFT with GGA is used to determine the structure and to calculate the electronic and optical properties of the chemically ordered KTa0.5Nb0.5O3 crystal (100), (110) and (111) surfaces. The results show that the surface properties are different from the bulk properties. The data obtained agree with the expected values and can serve as guidance for future experimental studies in the fields of photorefraction and nonlinear optics.

Relativistic Electromagnetic Soliton in Electron-Positron-Ion Plasma

Considering the limiting weak nonlinearity, we obtained the solution of the coupled equations describing the interaction of ultraintense laser with cold transparent multicomponent plasma. It was indicated that the ions tend to accumulate at the center of the soliton and have large velocity when we consider the mobile ions in the multicomponent plasma, which shows that the result is different from that of the Berezhianis analysis. The change of proportion of ions in the plasma has effects on the amplitude of vector potential and the maximum velocity of the soliton.

Bound states of the Klein-Gordon equation with vector and scalar Wood-Saxon potentials

The S-wave Klein-Gordon equation with vector and scalar Wood-Saxon potentials is solved, and the energy levels are given through an equation.

Research with KNbO3 Bulk and Surface Properties Based on Density Functional Theory

The geometrical structure optimization, band structure, density of states, and charge density contour of potassium niobate (KNbO3) in the bulk [100] direction and (100) surface are calculated and analyzed using density functional theory. The elastic constants, which can describe the bonding characteristics and structural stability, are also computed, and the dielectric function, which can be used to calculate all the other optical properties of the material, is evaluated. Local density approximation functional analysis using CASTEP software is also employed. Several similarities and differences are observed in the properties of the KNbO3 bulk and surface. Almost all of the calculated results for the bulk sample are twice those of the surface sample. The results are consistent with the experiment.

Coherent Mutually Pumped Phase Conjugation Induced with High-Efficiency by Self-Pumped Phase Conjugate Reflection

A new scheme of coherent mutually pumped phase conjugate (MPPC) reflection that depends on the formation of self-pumped phase conjugate reflection of another beam has been demonstrated in a Cu:KNSBN crystal. The dependences of the MPPC reflectivity on the intensity ratio of the two incident beams and on the incident position of the signal beam were measured. We obtain phase conjugate reflectivities of greater than 90% at 488 nm.

Design of ultra wideband microwave absorber effectual for objects of arbitrary shape

In this paper, we present the design of multilayer microwave absorbers comprised of CoFe alloy nano-particles and nano-flakes as fillers. The thickness of the unite layer is optimized by using the Genetic Algorithm. Efficient microwave absorptions over a wide frequency band and a range of incident angles are achieved by using multilayer absorbers. We show that the absorbers are effective not only for a planar surface but also for arbitrarily shaped objects as well.