Dy~(3+),Sm~(3+)共掺杂Ca_2A1[AlSiO_7]荧光粉的发光性质研究

采用高温固相反应法合成了一系列Dy~(3+)、Sm~(3+)单掺杂和共掺杂铝方柱石发光材料,详细地研究了Dy~(3+)、Sm~(3+)掺杂对铝方柱石的结构和发光性质的影响。XRD结果表明Dy~(3+)、Sm~(3+)离子单掺杂和共掺杂样品均形成了单相的铝方柱石结构化合物,并没有改变基质的晶体结构。发光光谱表明,通过调节Dy~(3+)、Sm~(3+)离子的掺杂比例,发光颜色可实现从黄色到黄白色的可控调节。此外,发射和激发光谱表明,Dy~(3+)与Sm~(3+)离子之间存在有效的光谱重叠,暗示着Dy~(3+)→Sm~(3+)的能量传递。荧光寿命衰减结果进一步证实Dy~(3+)与Sm~(3+)离子之间是一种无辐射共振能量传递方式。     

Current–voltage characteristic of BaTiO3−δ in its mixed n/p regime under oxygen potential gradients

Current (I)–voltage (V) characteristic under oxygen potential gradients was experimentally examined on single crystal BaTiO_3−δ in its mixed ion/electron/hole regime at 1000 °C. The variation of I vs. V appears similar to that of an n/p junction, but with the limiting slope (dI/dV) approaching the maximum and minimum possible equilibrium conductances in the given oxygen potential gradient as increasing forward and reverse bias, respectively. This characteristic has been precisely traced theoretically by using the partial ionic and electronic conductivities of BaTiO_3−δ as measured against uniform oxygen chemical potential in equilibrium state. The nonlinear characteristic is attributed to the redistribution of oxygen chemical potential that is caused by a non-vanishing gradient of the ionic transference number of the oxide under the given oxygen potential gradient. It is demonstrated that the bulk transport properties of a mixed conductor may be tailored by terminal voltage in a chemical potential gradient.     

The effect of microscopic features upon the transmissivity of enclosed laser ablated laminated metallised polymer films

A vacuum-deposited aluminium layer (20 nm) is sandwiched between two layers of laminated oriented polypropylene (OPP) film whose thickness varies from 20 to 40 μm. Selected areas of this sealed system were transparentised by the redistribution of the aluminium layer without breaking the seal or causing damage to the OPP film using a 75 W Q-switched Nd:YAG laser. The resultant transparentised films contain aluminium particles, distorted polymer areas and intact areas of the vacuum-coated aluminium layer. This paper investigates the effect of microscopic features upon the overall transmissivity of the laser-treated films and hence the quality of the transparentisation process.     

Ion synthesis and laser annealing of Cu nanoparticles in Al2O3

Al₂O₃ samples with Cu nanoparticles, synthesised by ion implantation at 40 keV with a dose of 1×10¹⁷ ion/cm² and a current density from 2.5 to 12.5 μA/cm², were annealed using ten pulses from a KrF excimer laser with a single pulse fluence of 0.3 J/cm². The copper depth distribution, formation and modification of metal nanoparticles under the ion implantation and laser treatment were studied by Rutherford backscattering (RBS), energy dispersive X-ray (EDX) analysis, atomic force microscopy (AFM) and optical spectroscopy. It was found that laser annealing leads to a reduction in the nanoparticle size without diffusion of metal atoms into the bulk. The change in particle size and the possibility for oxidation of the copper particles are examined in the framework of Mie theory. Calculations presented show that under excimer laser treatment, Cu nanoparticles are more likely to be reduced in size than to undergo oxidation. Received: 19 April 2001 / Accepted: 7 November 2001 / Published online: 23 January 2002     

Valuing of the critical layer thickness from the deading time constant of RHEED oscillation in the case of InxGa1−xAs/GaAs heterojunction

In this work, we have looked for the correlation between the observed decay of reflection high-energy electron diffraction intensity oscillation and the critical layer thickness in the case of strained In_xGa_1−xAs/GaAs heterojunctions. The value of deading time constant of oscillation depends on the mismatch and on growth parameters, too. The decay of oscillation was described by two deading time constants which are responsible for the influences of the parameters mentioned above. The critical layer thickness was valued from the deading time constant responsible for the influence of mismatch only. The critical layer thickness determined this way shows good agreement with the theoretical model.     

Laser induced copper electroless plating on polyimide with Q-switch Nd:YAG laser

The results of laser induced deposition of copper on polyimide substrate from copper electrolyte solution are reported. Unlike most work reported in the literatures where CW Ar⁺ lasers were used, a second harmonic (532 nm wavelength) Q-switch Nd:YAG laser was used for our experiments. The deposition process was conducted by laser-catalyzing of the polyimide surface and subsequent photothermal-accelerated reduction of copper-complex ions in an alkaline reducing environment. The characteristics of the deposited copper line were investigated in terms of laser beam scanning speed, and the number of scans. The surface morphology and chemical composition of the deposited copper were analyzed using field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDX). The optimum processing conditions have been identified. The copper deposit was found to adhere well to the substrate.     

Photoinduced phase transition accompanied with the changes in magnetic properties

Recently, many studies have been started in search for materials which show a photoinduced phase transition (PIPT). In this work, we review two systems as typical examples of PIPT accompanied with changes in magnetic characteristics; (1) organo-metal complex [Fe(2-pic)₃]Cl₂ EtOH (2-pic = 2-amino-methyl-pyridine) and (2) III-V based magnetic semiconductors (In_1-x , Mn _x )As. In the former case, we show several nonlinear characteristics in dynamical process of photoinduced spin state transition from low-spin to high-spin states. In the latter one, photocarrier-induced ferromagnetic order has been observed by both magnetic and transport measurements.     

双端抽运热容激光器温度特性分析

通过对激光二级管阵列双端抽运热容激光器晶体的分析,建立了热传导模型及边界条件.利用有限元方法模拟了晶体的温度场分布,并分别对抽运光斑直径、抽运持续时间、抽运光强和晶体端面尺寸等因素对温度场分布的影响进行了分析,得到了热容工作模式下的激光器温度特性.结果表明,晶体端面温差随抽运光斑直径的增大先增后减,存在一个极大值,并且在不同抽运光强下,出现端面温差极大点时的抽运光斑直径不变.     

A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd：YAG laser

We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By using a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

Cr,Tm:YAG晶体中的能量转移

通过对Cr:YAG、Tm:YAG和Cr,Tm:YAG晶体吸收光谱和发射光谱的比较,研究了Cr,Tm:YAG晶体中的能量转移过程.指出Cr3+→Tm3+能量转移过程中,无辐射能量转移占绝对优势.