Luminescent properties of La2LiTaO6:Mn4+ and its application as red emission LEDs phosphor

A novel phosphor, Mn⁴⁺ doped La₂LiTaO₆, was developed by solid-state reaction method. The luminescent spectra and emission efficiencies of La₂LiTaO₆:Mn _x ⁴⁺ (x = 0.001, 0.003, 0.005 and 0.01) were discussed. The effects of co-doped charge compensation ions, M = Mg²⁺, Ca²⁺, Na⁺, were investigated, respectively. The excitation spectra indicated that La₂LiTaO₆:Mn⁴⁺ could be effectively excited by both NUV light and blue light. The emission spectra of the phosphor exhibit a broadband ranging from 670 to 720 nm with the maximum at about 709 nm in deep red region. The co-doping of Mg²⁺ could significantly improve the luminescent properties of La₂LiTaO₆:Mn⁴⁺. Thus, phosphor La₂LiTaO₆:Mn⁴⁺, Mg²⁺ can serve as a key component to improve color rendering of blue-chip white-LEDs.     

Functional organic single crystals for solid‐state laser applications

Because of long‐range order and high chemical purity, organic crystals have exhibit unique properties and attracted a lot of interest for application in solid‐state lasers. As optical gain materials, they exhibit high stimulated emission cross section and broad tunable wavelength emission as similar to their amorphous counterpart; moreover, high purity and high order give them superior properties such as low scattering trap densities, high thermal stability, as well as highly polarized emission. As electronic materials, they are potentially able to support high current densities, thus making it possible to realize current driven lasers. This paper mainly describes recent research progress in organic semiconductor laser crystals. The building molecules, crystal growth methods, as well as their stimulated emission characteristics related with crystal structures are introduced; in addition, the current state‐of‐the‐art in the field of crystal laser devices is reviewed. Furthermore, recent advances of crystal lasers at the nanoscale and single crystal light‐emitting transistors (LETs) are presented. Finally, an outlook and personal view is provided on the further developments of laser crystals and their applications.     

Design and Synthesis of a New Terbium Complex-Based Luminescent Probe for Time-Resolved Luminescence Sensing of Zinc Ions

Luminescent probes/chemosensors based on lanthanide complexes have shown great potentials in various bioassays due to their unique long-lived luminescence property for eliminating short-lived autofluorescence with time-resolved detection mode. In this work, we designed and synthesized a new dual-chelating ligand {4′-[N,N-bis(2-picolyl)amino]methylene-2,2′:6′,2′-terpyridine-6,6′-diyl} bis(methylenenitrilo) tetrakis(acetic acid) (BPTTA), and investigated the performance of its Tb³⁺ complex (BPTTA-Tb³⁺) for the time-resolved luminescence sensing of Zn²⁺ ions in aqueous media. Weakly luminescent BPTTA-Tb³⁺ can rapidly react with Zn²⁺ ions to display remarkable luminescence enhancement with high sensitivity and selectivity, and such luminescence response can be realized repeatedly. Laudably, the dose-dependent luminescence enhancement shows a good linear response to the concentration of Zn²⁺ ions with a detection limit of 4.1 nM. To examine the utility of the new probe for detecting intracellular Zn²⁺ ions, the performance of BPTTA-Tb³⁺ in the time-resolved luminescence imaging of Zn²⁺ ions in living HeLa cells was investigated. The results demonstrated the applicability of BPTTA-Tb³⁺ as a probe for the time-resolved luminescence sensing of intracellular Zn²⁺ ions.     

改进的基于积分时间定标的红外焦平面阵列非均匀性校正算法(英文)

红外焦平面阵列各探测元响应的非均匀性降低了图像的质量和温度分辨率,定标类和场景类校正算法为解决该问题提供了可行的途径.传统的基于黑体定标的校正算法由于其简单有效而被广泛使用,但是其缺点在于依赖黑体及其相关控温装置.本文提出了一种改进的基于积分时间定标的两级校正算法.在保持入射辐射不变的情况下,首先通过改变积分时间得到系列响应数据,然后利用最小二乘法估计出两点校正所需的初始校正系数,并对不同积分时间下的响应数据进行初校正,最后估计出一点校正系数.实验结果证明该方法具有计算量小、校正准确度高的优点,可取得优良的校正效果,并易于在硬件平台中实现.     

ZnO three-dimensional hedgehog-like nanostructure: synthesis,growth mechanism and optical enhancement

The 3D hedgehog-like ZnO nanostructures were synthesized on Si substrate through chemical vapor deposition process. The morphology and structure of the products were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, as well as transmission electron microscopy. The ZnO 3D hedgehog-like architectures were found to consist of a central nucleus and multiple side-growing nanowires with diameter of 100–250 nm and length up to 10 µm. The growth mechanism of the hedgehog-like ZnO nanostructures was studied. It revealed a three-step process during the entire growth. Finally, room temperature photoluminescence spectra of ZnO 3D nanostructures showed that the center excitation would render much stronger PL emission intensity. Furthermore, simulation results indicated that the enhanced emission came from light-trapping-induced excitation light field enhancement.     

Tight focusing of a double-ring-shaped, azimuthally polarized beam

We study the focusing properties of a double-ring-shaped azimuthally polarized beam through an annular high NA objective lens. It is shown that a subwavelength focal hole (～0.5λ) with a quite long depth of focus (～26λ) is achieved near the focus. This kind of nondiffracting focal hole is called dark channel, which may have applications in atom optical experiments, such as with atomic lenses, atom traps, and atom switches.     

Terahertz-wave parametric oscillator with a misalignment-resistant tuning cavity

We demonstrate a terahertz-wave parametric oscillator (TPO) with a corner-cube resonator consisting of a corner-cube prism (CCP) and a flat mirror. By using the cavity configuration proposed in this Letter, the generation of tunable monochromatic terahertz (THz) waves can be achieved just by rotating the flat mirror instead of rotating the TPO cavity relative to the pump beam. The THz-wave output intensity and pulse width can be controlled periodically by rotating the CCP around the cavity axis. The TPO stability against cavity misalignment is significantly improved by at least 1 to 2 orders of magnitude compared with the conventional plane-parallel resonator configuration.     

Phases of supersymmetric gauge theories with flavors

We explore the phases of supersymmetric U(N) gauge theories with fundamental matter that arise as deformations of SQCD by the addition of a superpotential for the adjoint chiral multiplet. As the parameters in the superpotential are varied, the vacua of this theory sweep out various branches, which in some cases have multiple semiclassical limits. In such limits, we recover the vacua of various product gauge group theories, with flavors charged under some group factors. We describe in detail the structure of the vacua in both classical and quantum regimes, and develop general techniques such as an addition and a multiplication map which relate vacua of different gauge theories. We also consider possible indices characterizing different branches and potential relationships with matrix models.     

Study on the surface erosion route to the fabrication of TiO2 hollow spheres

Three-dimensional (3D) architecture of TiO₂ hollow sphere has many excellent and interesting performances that attract significant attention nowadays. In this paper, a simple surface erosion approach to the fabrication of TiO₂ hollow spheres via the hydrothermal process has been developed. The morphologies and the phase were characterized by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The results indicate that the anatase-type TiO₂ hollow spheres with a diameter of ∼1 μm are successfully synthesized. The shell thickness of TiO₂ hollow spheres is ∼150 nm and the size of hollow cavity is ∼600 nm. By the control experiments, the influence of ammonium fluoride and hydrogen peroxide on the hollow spherical structures was studied. Hydrogen peroxide acts as both the oxidant and the bubble generator, ammonium fluoride is crucial for the erosion and dissolution of titanium, the detailed dissolution-crystallization mechanism for the formation of TiO₂ hollow spheres was also proposed.     

Guiding Neutral Atoms with Two Current-Carrying Wires and a Vertical Bias Field on the Atom Chip

We demonstrate the guiding of neutral atoms with two parallel microfabricated current-carrying wires on the atom chip and a vertical magnetic bias field. The atoms are guided along a magnetic field minimum parallel to the current-carrying wires and confined in the other two directions. We describe in detail how the precooled atoms are efficiently loaded into the two-wire guide. We present a detailed experimental study of the motional properties of the atoms in the guide and the relationship between the location of the guide and the vertical bias field. This two-wire guide with vertical bias field can be used to realize large area atom interferometer.