表面等离子体激元微盘的优化设计及应用

表面等离子体激元(SPP)微腔具有很高的品质因子和极小的模式体积,在光电子器件研究方面具有重要的应用价值。采用有限元法对表面等离子体激元的金属覆盖介质微盘谐振腔进行理论模拟,研究考虑微盘底半径、介质层厚度及金属膜厚度等参数对微盘表面等离子体模的品质因子及模体积的影响。研究表明,在光通信波段1550nm附近获得高品质因子(1000以上),极低模式体积的表面等离子体微盘。最后研究了利用优化设计的微盘进行折射率传感的应用,获得了高达300nm/RIU的折射率传感灵敏度。     

欠采样包裹相位图的展开算法

利用四种常见算法对由球面参考光像面数字全息显微术得到的中药饮片海金沙细胞的包裹相位图进行了相位解包裹。结果表明：基于离散余弦的最小二乘算法和预条件共轭梯度算法会使欠采样区域的误差进行传递,使得解包裹相位产生较大误差;质量图导向路径跟踪算法由于未识别残差点,导致出现拉线或者孤岛区域,而且处理速度很慢;基于横向剪切干涉的最小二乘算法处理欠采样包裹相位图的效果最好,而且处理速度较快。     

金纳米球壳对的局域表面等离激元共振特性分析

应用有限元方法, 研究金纳米球壳对的几何结构参数及物理参量对其表面等离激元共振的散射及消光光谱的影响, 并根据等离激元杂化理论进行了理论分析. 结果表明, 随着金壳厚度的增加, 金纳米球壳对的散射及消光共振峰先发生蓝移而后红移, 而随着金纳米球壳间隙的减小, 或者随着金纳米球壳的内核尺寸或内核介质折射率的增大, 散射及消光共振峰均发生红移; 随着金壳厚度或内核尺寸减小, 或者随着内核介质折射率增大, 金纳米球壳对的散射与消光共振强度减弱, 而随着金壳间隙的减小, 金纳米球壳对的散射共振强度先增强后减弱, 而消光共振强度逐渐增强, 数值模拟与理论分析一致.     

Large spot size and low-divergence angle operation of 917-nm edge-emitting semiconductor laser with an asymmetric waveguide structure

GaInAs/AlGaAs comprehensive-strained three-quantum-well lasers with asymmetric waveguide are designed and optimized. With this design, the optical field in the transverse direction is extended, and a semiconductor laser with large spot is obtained. For a 300-μm cavity length and 100-μm aperture device under continuous wave (CW) operation, the measured vertical and horizontal far-field divergence angles are 12.2° and 3.0°, respectively. The slope efficiency is 0.44 W/A and the lasing wavelength is 917 nm.The equivalent transverse spot size is 3 μm for the fundamental transverse mode, which is a sufficiently large value for the purpose of coupling and manipulation of light.     

地下强爆炸辐射流体动力学过程的二维数值模拟

为评估强爆炸的毁伤效应,利用流固耦合界面处理方法,考虑辐射输运引起的能量沉积过程,建立同时求解辐射流体力学方程和流体弹塑性方程的二维耦合计算方法,给出地下强爆炸时,爆室内辐射波传播、辐射能量沉积到岩土表层、岩土表层膨胀、冲击波在岩土介质中传播、爆室内高压压缩爆室壁、爆室壁振荡增大的完整物理过程.     

Propagation properties of Lorentz beam in uniaxial crystals orthogonal to the optical axis

The properties of Lorentz beams propagating in uniaxial crystals orthogonal to the optical axis are studied. The diffraction field components and effective beam sizes of the Lorentz beams are derived in analytical forms. Numerical results show that, upon propagating in uniaxial crystals, a Lorentz beam loses its initial Lorentz type distribution. Also, after propagating for sufficient distances, the transverse components would finally convert into a specific four-petal profile with an axial shadow, which may find applications in the optical trapping of particles. It also shows that the Lorentz beam parameters w_0x, w_0y and the ratios of refractive indices have strong influences on the diffraction field components and on the effective beam sizes when propagating in uniaxial crystals.     

Analytical modeling and experimental investigation of laser induction hybrid rapid cladding for Ni-based WC composite coatings

Laser induction hybrid rapid cladding (LIHRC) cannot only increase the cladding efficiency, but can also eliminate porosity and cracking of ceramic–metal composite coatings. In order to obtain a deep understanding of LIHRC with rapid cladding speed and high powder deposition rate, an analytical model of LIHRC for Ni-based WC composite coatings is proposed in the paper. The predictions of cladding height and powder efficiency obtained with this model are in good agreement with experimental results. Injection angles at which the attenuation rate of laser power is relatively low are identified and crack-free composite coatings with smooth surface, good profile and metallurgical bonding to substrate can be obtained. The calculated results for the temperature of the powder particles are compared to experimental data of the microhardness profiles and show a similar trend.     

The refractive index distribution of even polygonal selfoc lens

MATLAB diffusion partial differential toolboxes are used to solve the ion diffusion equation under even polygonal boundary conditions, such as square and hexagon, and obtain the dynamic process ion concentration during ion exchange. The exact solutions of the refractive index distribution are proved by the correctness. The ion concentration equation in even polygonal glass rod is calculated by the variable separation and coordinate transformation method. The computation results are in good agreement with the measured ones in the compound eye system.     

The 2-D growth of gold on single-layer graphene/Ru(0001): Enhancement of CO adsorption

The growth and morphology of two-dimensional (2-D) gold islands on a single-layer graphene supported on Ru(0001) have been studied by scanning tunneling microscopy (STM). Our findings show that gold exhibits 2-D structures up to a gold dosage of 0.75 equivalent monolayers, and that these 2-D gold islands are thermally stable at room temperature. Parallel polarization modulation infrared reflection absorption spectroscopic (PM-IRAS) and high resolution electron energy loss spectroscopic (HREELS) studies indicate that carbon monoxide (CO) adsorbs on these 2-D gold islands at 85 K, showing a characteristic CO stretching feature at 2095 cm^? 1 for a saturation coverage of CO. The red shift of the CO stretching frequency compared to that on charge neutral gold is consistent with electron transfer from graphene to gold, i.e., an electron-rich gold overlayer. Preliminary data obtained by dosing molecular oxygen onto this CO pre-covered surface suggest that the 2-D gold islands catalyze the oxidation of CO.     

Preparation of solution-based YBCO films with BaSnO3 particles

The YBCO films with BaSnO₃ (BSO) particles were prepared on LAO (0 0 1) substrates by metal organic deposition using trifluoroacetates (TFA-MOD) via introducing SnCl₄ powders into the YBCO precursor solution. It was found that with the increase of the SnCl₄ contents, the slower decomposition and higher temperature for nucleation during the reaction were requested compared to that of pure YBCO film. The YBCO films with different contents of Sn with dense surface and well c-alignment were obtained under optimized heat treatment, and the BaSnO₃ phases were detected by XRD analysis. Litter effect of BSO particles on the T_c and J_c values of YBCO films was found. All YBCO films with BSO particles had T_c values over 90 K and J_c values over 1 MA/cm². A significant enhancement of J_c was observed for YBCO films with BSO particles compared to that of pure YBCO film by the field dependence of J_c values. The best property was obtained for YBCO film with 6 mol.% Sn at 77 K under magnetic field. The results showed that the J_c value of YBCO film with 6 mol.% Sn was enhanced by a factor of 2 in 2 T, and over a factor of 10 beyond 4 T compared to that of pure YBCO film.