非简并双光子Jaynes-Cummings模型中贝尔非定域性的演化

基于赝自旋算符的关联所对应的贝尔算符期待值,研究了各种双模非经典态(纠缠相干态、对相干态以及双模压缩真空态)在非简并双光子Jaynes-Cummings模型中贝尔非定域性的动力学特性.结果表明:对于纠缠相干态,贝尔非定域性的演化与双模场平均光子数的大小息息相关;对于对相干态和双模压缩真空态,贝尔非定域性会在有限的时间内完全消失,之后又基本上复原到初始值,呈现出周期性振荡现象.     

The effect of spherical aberration on the phase singularities of focused dark-hollow Gaussian beams

The phase singularities of focused dark-hollow Gaussian beams in the presence of spherical aberration are studied. It is shown that the evolution behavior of phase singularities of focused dark-hollow Gaussian beams in the focal region depends not only on the truncation parameter and beam order, but also on the spherical aberration. The spherical aberration leads to an asymmetric spatial distribution of singularities outside the focal plane and to a shift of singularities near the focal plane. The reorganization process of singularities and spatial distribution of singularities are additionally dependent on the sign of the spherical aberration. The results are illustrated by numerical examples.     

Microwave-assisted synthesis of flower-like and leaf-like CuO nanostructures via room-temperature ionic liquids

Flower-like and leaf-like cupric oxide (CuO) single-crystal nanostructures have been successfully synthesized using ionic liquid 1-octyl-3-methylimidazolium trifluoroacetate ([Omim]TA) under the microwave-assisted approach. By controlling the concentration of [Omim]TA and reaction temperature, shape transformation of CuO nanostructures could be achieved in a short period of time. The results indicate that ionic liquid [Omim]TA plays an important role in the formation of different morphologies of CuO crystals. The crystal structure and morphology of products were characterized by X-ray powder diffraction (XRD), infrared spectrum (IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), and selected-area electron diffraction (SAED). A possible mechanism for CuO nanostructure was proposed. In addition, UV-vis spectroscopy was employed to estimate the band gap energies of CuO crystals.     

Coupling coefficients evaluation of a directional coupler using gain guided and index antiguided fibers

In this paper, we have investigated the mutual and self coupling characteristics of directional couplers using two individual gain guided and index antiguided fibers, which can deliver robust single mode operation with large mode area, respectively owing to the combined adequately large gain coefficients in the core; Some interesting and distinguishing properties from conventional index guided fiber couplers are obtained that: The variations of coupling coefficients are complex-valued and spatially damping oscillated, but not exponential-like decreasing as conventional index guided couplers.     

A Monte Carlo study of the thermodynamic properties of a quasi-one-dimensional organic polymer ferromagnet

The thermodynamic properties of a quasi-one-dimensional organic ferromagnet at different temperatures and in different applied magnetic fields have been investigated by means of the Heisenberg model combined with the Monte Carlo method. The results indicate that a peak in the magnetic susceptibility is obtained at low temperatures. Furthermore, the effect of dimerization on the magnetic properties has also been studied. We find that the dimerization suppresses the magnetization in this model. The ferromagnetic couplings between the side-free radicals stabilize the ferromagnetism and increase the apparent Curie temperature.     

High-spin states in neutron-rich 102Mo nucleus

High-spin states in neutron-rich 102Mo nucleus have been studied by measuring the prompt γ-rays in the spontaneous fission of 252Cf. The previous level scheme has been updated and some new levels and transitions are identified. The one-phonon γ-band is expanded and a band head level of the two-phonon γ-band is proposed. The systematic characteristics of yrast bands, one-phonon γ-bands, two-phonon γ-bands and quasi-particle bands in 102Mo, 104Mo and 106Mo are discussed.     

Bulk-sensitive spectroscopic studies on noncentrosymmetric superconducting system of Mg–Ir–B

We present the data from ultrahigh-resolution laser-excited photoemission spectroscopy on a newly discovered noncentrosymmetric superconductor Mg₁₀Ir₁₉B₁₆. We observed the evidences for the opening of superconducting gap where numerical fittings show that isotropic s-wave model can satisfactorily explain the behavior of spectra near the Fermi level. We also present the valence band photoemission spectrum and B K fluorescence spectrum to discuss the basic electronic structure of Mg₁₀Ir₁₉B₁₆.     

Polarized spectral properties of Pr3+ ions in NaGd(MO4)2 crystal

A Pr³⁺:NaGd(MoO₄)₂ single crystal has been grown by the Czochralski method. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves of the crystal were measured at room temperature. The Judd–Ofelt intensity parameters Ω _t,q (t=2,4,6) and the spectroscopic parameters related to the ³ P ₀ and ¹ D ₂ multiplets were obtained and analyzed. The decay mechanisms for the ³ P ₀ and ¹ D ₂ multiplets were also discussed.     

Preparation and characterization of Fe3O4 magnetic composite microspheres covered by a P(MAH-co-MAA) copolymer

A magnetic core–shell-layered polymer microsphere (MPS) was successfully synthesized by a dispersion polymerization route, where the modified Fe₃O₄ nanoparticles (MFN) were used as a core, while poly(maleic anhydride-co-methacrylic acid) P(MAH-co-MAA) as a shell was covered on the surface of the Fe₃O₄ nanoparticles. Environmental scanning electron microscope (ESME) and transmission electron microscope (TEM) measurements indicate that the magnetic P(MAH-co-MAA)/Fe₃O₄ composite microspheres assume sphericity and have a novel core–shell-layered structure. The crystal particle sizes of the unimproved Fe₃O₄ and the MFN samples vary from 8 to 16 nm in diameter, and the average size is about 10.6 nm in diameter. The core–shell magnetic composite microspheres can be adjusted by changing the stirring speed. Since multiple Fe₃O₄ cores were coated with a proper percentage of P(MAH-co-MAA) copolymers, and therefore lower density was acquired for the MPS, which improved sedimentation and dispersion behavior. The saturated magnetization of pure Fe₃O₄ nanoparticles reaches 48.1 emu g⁻¹ and the value for composite nanoparticles was as high as 173.5 emu g⁻¹. The nanoparticles show strong superparamagnetic characteristics and can be expected to be used as a candidate for magnetism-controlled drug release.     

Spectrally selective splitters with metal-dielectric-metal surface plasmon waveguides

Spectrally selective splitters with metal-dielectric-metal (MDM) subwavelength waveguides are proposed in this paper. The method is based on the Bragg grating structure with periodically modulated MDM waveguide width, which delivers a stop band effect for the surface plasmon propagating in the waveguide. By adding appropriate Bragg grating structure in one or more arms of the waveguide splitters, light in a certain frequency range can be readily guided into the desired directions, as demonstrated numerically by the finite-difference time-domain method. Dependence and optimization of the geometrical parameters are also considered in this paper.