High-bandwidth and low-loss photonic crystal power-splitter with parallel output based on the integration of Y-junction and waveguide bends

A 1×2 power-splitter with parallel output that exhibits high-bandwidth and low-loss splitting for TE-polarized light is designed based on a photonic crystal slab in a silicon-on-insulator (SOI) material. The high performance is achieved by the integration of a Y-junction and 60° waveguide bends, which is designed to ensure single-mode operation, and keep the output channels of the power-splitter be parallel to the input channel. With a three-dimensional finite-difference time-domain (3D-FDTD) technique, ultralow-loss output of the optimized power-splitter with normalized transmission above 45% (in the range 3.216±0.18 dB) is obtained in the high-bandwidth range 1472–1634 nm, which covers the entire C-band of optical communication. In addition, the simulation results demonstrate that when the manufacture error of the lattice shift (dx) is in the range of ±10 nm, the disturbance of the transmission and the bandwidth are 1.52% and 6.79%, respectively. Both the specific result and the general idea of integration design are promising in the optical integrated circuit (OIC) and integrated optical devices in the future.     

Ionic liquid-assisted hydrothermal synthesis of dendrite-like NaY(MoO4)2:Tb phosphor

Micro-sized NaY(MoO₄)₂:Tb³⁺ phosphors with dendritic morphology was synthesized by a ionic liquid-assisted hydrothermal process. X-ray diffraction (XRD) indicated that the as-prepared product is pure tetragonal phase of NaY(MoO₄)₂. Field emission scanning electron microscopy (FE-SEM) images showed that the as-prepared NaY(MoO₄)₂:Tb³⁺ phosphors have dendritic morphology. The photoluminescent (PL) spectra displayed that the as-prepared NaY(MoO₄)₂:Tb³⁺ phosphors show a stronger green emission with main emission wavelength 545 nm corresponding to the ⁵D₄→⁷F₅ transition of Tb³⁺ ion, and the optimal Tb³⁺ doping concentration for obtaining maximum emission intensity was confirmed to be 10 mol%. Based on Van Uitert's and Dexter's models the electric dipole–dipole (D–D) interaction was confirmed to be responsible for the concentration quenching of ⁵D₄ fluorescence of Tb³⁺ in the NaY(MoO₄)₂:Tb³⁺ phosphors. The intrinsic radiative transition lifetime of ⁵D₄ level is found to be 0.703 ms.     

Metal enhanced photoluminescence of near-infrared CdTexSe1−x quantum dots

High-quality alloyed near-infrared CdTe_xSe_1?x quantum dots were synthesized by a modified organometallic method. The emission wavelength of the alloyed quantum dots were turned from visible to near-infrared range by changing the composition of the precursor. The photoluminescence intensity of the alloyed quantum dots was further enhanced by coupling through localized surface plasmons from Au nanoparticles. The alloyed CdTeSe quantum dots coupled with Au nanoparticles exhibited a 4 times photoluminescence enhancement than that of bare CdTeSe quantum dots by turning the localized surface plasmons resonant absorption of Au nanoparticles consistent to the excitation wavelength. This method will be beneficial for the potential applications in the biological imaging and detection.     

Low-temperature electrolytic coloration and spectral property of ammonium alum crystals

Ammonium alum crystals are colored electrolytically using a pointed cathode and a flat anode at low temperatures and under various voltages. SO₃^?, SO₂^? and O₃^? hole-trapped centers are produced in colored ammonium alum crystals. Characteristic absorption bands of SO₃^?, SO₂^? and O₃^? hole-trapped centers are observed in absorption spectra of colored ammonium alum crystals. Production and conversion of hole-trapped centers are explained. Current–time curves for electrolytic coloration of ammonium alum crystal and their relationship with electrolytic coloration process are given.     

红外分光光度法测定水体中石油类及萃取剂的选择

与重量法、紫外分光光度法、荧光分光光度法和非分散红外法相比,红外分光光度法具有灵敏度高、适用范围广和测定结果受标准油品及样品中油品组成影响较小的优点。在萃取剂的选择上,建议采用六氯四氟丁烷(S-316),它具有毒性小,萃取率高,准确度和精密度好等特点,完全可用作测定水与废水中石油类的提取剂。     

ICP-OES法测定穿心莲药材中6种重金属元素溶出特性的研究

以电感耦合等离子体发射光谱法(ICP-OES)同时测定了中药穿心莲中的As,Ba,Cd,Cr,Cu,Pb等6种重金属元素,方法相对标准偏差2.1%~4.6%,回收率92.0%~103.2%,灵敏度高、简单、准确可靠。考察了采用热回流提取、浸泡提取、超声辅助提取等不同提取方法和提取溶剂时,上述6种元素的溶出情况。结果表明,实验所用穿心莲药材中Ba的含量最高,其次为Cu和Cr,而As,Pb,Cd在药材中含量相对较低。随着提取溶剂中乙醇含量升高,Ba的溶出减少,而Cu、Cr的溶出增加,Cd在酸性溶液中溶出最多;提取方法则以冷浸法溶出重金属元素最少,使用纯水和碱水的热回流提取重金属元素溶出相对较多。以上差异可能与这些元素在药材中的存在形态有关。     

Instrumentation of coherent X-ray imaging and the primary experimental results

Coherent X-ray microscopy has advanced towards higher-energy, more brilliant sources over the past decade since its demonstrations, and many advancements have been made towards optimizing this imaging technique. Here we present both the experimental instrument for obtaining diffraction patterns and the primary reconstruction of yeast cell 2D projection. In addition, the characteristics of the existing optics at BL29XUL of SPring-8 Facility and the method of image reconstruction are discussed.     

Resonance modes in optical fibres

The weakly nonlinear boundary value problem of wave propagation in an optical fibere(for the transverse electric mode,for example)is formulated and a modified linear solution is obained.It is shown that a self-consistent theory of fibre optics should be weakly nonlinear,The mode of critical refraction that does not exist in the linear theory is obtained,showing that it is a mode consisting of resonance modes,It is shown that the signal carriers in a long fibre are of resonance modes,not normal modes,Some experimental data are given for comparison with the theoretical predictions and the agreement seems satisfactory.     

Generation and Quantum Interference of Entangled Electron-Hole Pairs in a Hanbury Brown and Twiss Interferometer

The Hanbury Brown-Twiss interferometer is proposed to serve as a detector of the crossed Andreev reflection and to generate entangled electron-hole pairs. It is shown that the non-local electron and hole induced by the crossed Andreev reflection are entangled. Quantum interference of the entangled electron-hole pairs gives rise to a new measurable effect of the phase difference between two superconductors in the cross correlation. The present theoretical predictions can be experimentally realized within the present-day microelectronic technology.     

Elimination of surface scratch/texture on the surface of single crystal Si substrate in chemo-mechanical grinding (CMG) process

Si wafers are widely used as a substrate material for fabricating ICs. The quality of ICs depends on the quality of Si wafers. The chemo-mechanical grinding (CMG) with soft abrasive grinding wheels (SAGW) has been recently found to be a great potential process for machining Si wafers to generate superior surface quality at low cost. However, there have been very few studies on observing variation of topography of scratch/texture and understanding basic eliminating process of scratch/texture on the ground Si wafer. Furthermore, few reports on the variation of surface roughness and material removal rate (MRR) during CMG process and relationship between MRR and surface roughness during CMG process are presented. In this paper, a series of CMG experiments have been conducted to study the elimination process of artificial scratches created on etched Si surfaces and residual textures induced by SD1500 diamond wheel in CMG process, and to understand the topography variations of Si surfaces and some basic grinding characteristics during CMG process.