Tunable intensity of the spectral reflectance of a guided-mode resonance filter with dual channels

Simulating the characteristics of a guided-mode resonance filter with rigorous coupled wave analysis, we find that, by adjusting the azimuthal angle of the grating used as a sub-layer of the guided-mode resonance filter from 0° to 90° under TE-reflectance, the intensity of the spectral reflectance of the guided-mode resonance filter monotonically increases at the wavelength of 684.6 nm, while the spectral reflectance monotonically decreases at the wavelength of 723 nm. Moreover, the spectral reflectance with TE-reflectance at 90° corresponds to the TM-reflectance at 0°. The phenomenon means that the intensity of the spectral reflectance can be easily tuned with different azimuthal angles by choosing appropriate structure parameters of the guided-mode resonance filter.     

High-efficiency guided-mode resonance filter

A high-efficiency guided-mode resonance reflection filter is reported. The device consists of a surface-relief photoresist grating and an underlying HfO (2) waveguide layer deposited on a fused-silica substrate. The spectral response measured with a dye-laser beam at normal incidence exhibited a peak reflectance of 98% at a wavelength of 860 nm with sideband reflectance below ~5% extending over the wavelength range provided by the dye (800-900 nm). At normal incidence the filter linewidth was 2.2 nm. High-efficiency double-peak resonances occurred at nonnormal incidence, with the spectral locations of the maxima vayring with the incidence angle. The filter response at various angles of incidence agreed well with the theoretically calculated reflectance curves.     

一种高精度偏振遥感探测方式的精度分析

检偏器的角度误差是影响偏振遥感探测精度的重要因素之一,是许多高精度定量化偏振遥感需要考虑的一个问题。在检偏器(0°,60°,120°)放置的测量系统中,当入射光偏振角接近于0°或180°时偏振测量易产生最大误差值,而偏振角接近30°,90°和150°时,偏振度的测量具有很高的精度;在检偏器(0°,45°,90°)放置方式中,偏振角接近45°的光束测量易具有最大误差值,而偏振角接近于0°,90°和135°时,角度误差对偏振度测量精度的影响很小。除了个别偏振角外,对高偏振度入射光束的偏振测量通常具有较大的偏振测量误差。因此,引进线偏振光的平均偏振度测量精度描述偏振测量装置的优劣,结果表明检偏器(0°,60°,120°)放置方式优于检偏器(0°,45°,90°)放置方式。     

激光入射角度对薄膜热场分布影响的数值分析

在多层介质薄膜中，激光的入射方式是影响薄膜抗损伤能力的关键因素之一.提出了一种模拟锥角高斯光入射多层介质薄膜后电场和热场分布的方法.该方法能够分析薄膜中高斯光各个角谱分量叠加形成的电场分布，进而得到由于薄膜本征吸收产生的热量沉积以及薄膜内部的温度场分布.针对中心波长为4.3 μm的中红外高反膜进行了分析，给出了高反膜系的温升峰值随激光入射角度和偏振态的变化.结果表明：对于s偏振光，斜入射时膜系的最高温升峰值高于垂直入射峰值，而p光的结果则相反.此种模拟方法克服了原有方法对激光入射角度的限制，较好地反映出斜入射情况下激光偏振态对薄膜损伤的影响. 关键词： 多层介质薄膜 高斯光 热过程 数值分析     

A Three-Dimensional Ray-Tracing Study of R-X Mode Waves during High Geomagnetic Activity

We further present a three-dimensional (3D) ray-tracing study on the propagation characteristic of the superluminous R-X mode waves during high geomagnetic activity following our recent two-dimensional results [J. Geophys. Res. 112(2007)A10214]. We perform numerical calculations for this mode which originates at specific altitude r=2.0R_E in the source cavity along a 70° night geomagnetic field line. We demonstrate that the ray path of the R-X mode is essentially governed by the azimuthal angle of the wave vector k. Ray paths starting with azimuthal angle 180° (or in the meridian plane) can reach the lowest latitude, but stay at relatively higher latitudes with the azimuthal angles other than 180° (or off the meridian plane). The results further supports the previous finding that the R-X mode may be physicallypresent in the radiation belts under appropriate conditions.     

The reflection and polarization properties of non-spherical aerosol particles

In this paper, we investigate the capability of multi-angle TOA reflectance and polarized reflectance for the retrieval of aerosol properties including aerosol mode (fine mode and coarse mode), aerosol shape (sphere and non-spherical), and aerosol optical thickness. Single-scattering parameters and phase-matrix elements were computed for randomly oriented non-spherical aerosol particles. Sensitivity indices were introduced to quantify the sensitivity of the TOA total reflectance and polarized reflectance to aerosol parameters. Finally, on the basis of the sensitivity study, this paper presents a conceptual approach toward the remote sensing of non-spherical aerosol three parameters (aerosol mode, aerosol shape, and aerosol optical thickness) using the TOA total reflectance and TOA polarized reflectance for the 0.865 μm spectral bands measured at multiple viewing angles.     

Azimuthal Correlations of Fragments with Light Charged Particles in Reaction of 25MeV/u 40Ar+115In

The large angle correlations for in-plane and out-of-plane have been measured for the pairs of the fragments and light charged particles (LCPs) in the reaction of 25MeV/u ⁴⁰Ar+¹¹⁵In. The azimuthal correlation functions and the azimuthal asymmetry factors were obtained. The azimuthal correlation functions of all pairs between fragments and a particles are of minimum value in φ=90°plane. It indicates that the LCPs and fragments formed in the reaction exhibit an enhanced emission in the reaction plane due to collective rotation-like effect induced by attractive mean field. The more heavier the masses of the coincident LCPs and fragments are, the more stronger the left-right asymmetries of the coincident particles with respect to the beam direction in the reaction plane are, the more preferential the particle emission to the direction opposite to the coincident reaction products is. Along with the increase of the mass of the coincident LCPs and fragments, the influences of the sequential decay and particle final state interactions on the azimuthal correlation functions of the correlated pairs in the φ=0° plane decrease and vanish at last, the collective rotation-like effect is enhanced, and the azimuthal asymmetries increase.     

Assessing epithelial cell nuclear morphology by using azimuthal light scattering spectroscopy

We describe azimuthal light scattering spectroscopy (phi/LSS), a novel technique for assessing epithelial-cell nuclear morphology. The difference between the spectra measured at azimuthal angles phi = 0 degrees and phi = 90 degrees preferentially isolates the single backscattering contribution due to large (approximately 10 microm) structures such as epithelial cell nuclei by discriminating against scattering from smaller organelles and diffusive background. We demonstrate the feasibility of using phi/LSS for cancer detection by showing that spectra from cancerous colon tissue exhibit significantly greater azimuthal asymmetry than spectra from normal colonic tissues.     

利用多角度光谱数据探测冬小麦氮素含量垂直分布方法研究

作物氮素具有随植株高度层垂直分布的特性,快速、无损探测作物氮素垂直分布状况,对于指导合理施肥、提高肥料利用率和减少环境污染具有重要意义。本文提出了利用偏最小二乘(partial least square,PLS)算法,运用多角度光谱数据估计冬小麦氮素含量垂直分布的方法。分别选用前向和后向不同观测角度组合形成的光谱数据组建植被指数,建立不同高度层的叶片氮素含量探测模型,其中选用±50°和±60°的组合,建立了冬小麦上层叶位叶片氮密度反演模型;选用±30°和±40°的组合,建立了中层叶位叶片氮密度反演模型;选用±20°和±30°的组合,建立了下层叶位叶片氮密度反演模型。针对氮素反演容易受到作物背景(土壤、作物残渣)影响的问题,引入R₇₀₀/R₆₇₀比值,改进七种常见的植被指数,利用改进了的植被指数建立了冬小麦上层、中层、下层叶片氮密度垂直分布模型。建模实验结果改进了叶片氮密度上层、中层、下层垂直分布估算结果,验证实验选取建模实验中表现最好的三个植被指数进行进一步研究,结果表明改进后的绿光归一化植被指数(green normalized difference vegetation index,GNDVI)在反演上层、中层、下层叶片氮密度时效果最好,达到了极显著的水平,可用于植被氮素含量的垂直分布探测。     

Nano-structural characteristics and optical properties of silver chiral nano-flower sculptured thin films

Silver chiral nano-flowers with 3-, 4- and 5-fold symmetry were produced using oblique angle deposition method in conjunction with the rotation of sample holder with different speeds at different sectors of each revolution corresponding to symmetry order of the acquired nano-flower. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM), were employed to obtain morphology and nano-structure of the films. Optical characteristics of silver chiral nano-flower thin films were obtained using single beam spectrophotometer with both s- and p-polarization incident light at 30° and 70° incidence angles and at different azimuthal angles (φ). Optical spectra showed both TM (TDM (transverse dipole mode) and TQM (transverse quadruple mode)) and LM (longitudinal mode) Plasmon resonance peaks. For 3- and 4-fold symmetry chiral nano-flowers the s-polarization extinction spectra obtained at different azimuthal angles did not show significant change in the Plasmon peak position while 5-fold symmetry chiral nano-flower showed a completely different behavior, which may be the result of increased surface anisotropy, so when the φ angle is changed the s-polarization response from the surface can change more significantly than that for lower symmetries. In general, for 3-, 4- and 5-fold symmetry chiral nano-flowers a sharp peak at lower wavelengths (<450 nm) is observed in the s-polarization spectra, while in addition to this peak a broad peak at longer wavelengths (i.e., LM) observed in the p-polarization spectra, which is more dominant for 70° incidence angle.     

Electronic structure, optical properties and lattice dynamics of MgSO3·6H2O

The electronic band structure, optical properties and lattice vibrations of MgSO(3)·6H(2)O were studied within density functional theory and compared to the experimental optical data and polarized Raman spectra. Due to the 'molecular' nature of the MgSO(3)·6H(2)O crystal all Γ-point phonon modes could be separated into groups belonging to specific structural blocks: Mg(H(2)O)(6) octahedra, SO(3) units and H(2)O molecules. All Raman lines in the experimental spectra are assigned to definite vibrations of the structure and reasonable agreement is found between theoretical and experimental mode frequencies. The temperature-dependent Raman spectra reveal at 60 °C a sharp transition from MgSO(3)·6H(2)O to anhydrous amorphous MgSO(3) without the noticeable presence of intermediate lower hydrates, such as MgSO(3)·3H(2)O.     

加载角度和线型缺口对锂离子电池隔膜拉伸性能的影响

锂离子电池隔膜作为防止正负极接触的物理屏障,其结构完整性对于电池安全至关重要。进行了4种商业隔膜单轴拉伸实验,分析加载角度和线型缺口对隔膜材料拉伸强度、弹性模量、断裂模式的影响。结果表明:无缺口试样在0°方向上的拉伸强度最大,90°方向上拉伸强度最小;当两个无缺口试样的加载角度互为补角时,它们的拉伸强度接近。对于缺口试样而言,缺口方向沿着90°的试样有最大破坏载荷;线型缺口试样有更高的弹性模量,但是塑性变形大幅减少。无缺口试样和缺口试样在拉伸过程中的断裂模式相同,即除0°试样沿横向断裂外,其他加载角度的试样均沿着纵向断裂。     

不同融化状态雪的偏振特性分析

在当今全球变暖的形势下,传统对于固态雪的研究已无法满足需求,文章定性分析了不同融化状态雪的偏振反射光谱,重点探讨了偏振角、方位角、光线入射天顶角和探测天顶角与不同融雪类型的关系,发现这些因素对不同融雪类型的偏振反射光谱均有影响。在可见光波段,融雪在90°偏振时的反射比最大,0°偏振时最小;探测角与入射角越大时,融雪的偏振反射比也越大;不同方位角时的融雪偏振反射光谱出现异于其他地物光谱的反常现象;某些波段的偏振光谱特征对判断融雪含水量大小具有一定意义;同时随着含水量的增加偏振反射比显著下降。这些规律为以后利用偏振光谱定量分析融雪特性奠定了基础,同时在淡水资源管理和监测春汛等自然灾害方面也有一定的现实意义。     

优化重聚脉冲提高梯度场核磁共振信号强度

缩短射频脉冲宽度, 有助于解决脉冲电力消耗大、样品吸收率高、信噪比低等极端条件核磁共振探测的关键问题. 本文首先分析射频脉冲角度对核磁共振自旋回波信号强度的影响机理, 基于Bloch方程推导了回波信号幅度与扳转角、重聚角的关系. 在特制核磁共振分析仪上采用变脉冲角度技术, 分别在均匀磁场和梯度磁场条件下实现对扳转角和重聚角与回波信号强度关系的数值模拟和实验测量. 结果表明, 梯度场中, 扳转角为90°、重聚角为140°的射频脉冲组合获得最大首波信号强度, 比180°脉冲对应的回波幅值提高13%, 能耗降低至78%. 选用该重聚角(140°) 优化设计饱和恢复脉冲序列探测流体的纵向弛豫时间T₁特性, 准确获得 T₁分布.该结果对于低电力供应、且对信噪比有较高要求的核磁共振测量, 如随钻核磁共振测井和在线核磁共振快速检测等, 具有重要意义. 关键词： 核磁共振 信号强度 重聚脉冲角度 Bloch方程     

Trace Distance of Remote State Preparation Through Noisy Channels

In this paper, we study remote state preparation (RSP) by w state through noisy channels. The trace distance is used to describe how close the original state is to the output state. Studies show the trace distance is a function of decohenrence rates and angles of the state to be prepared. At the same time, we investigate the influence of different types of noises on the trace distance and find the various types of noises have different degrees of influence on the trace distance for a definite qubit. We also study changes of the trace distance against polar and azimuthal angles.     

Theoretical analysis of double-differential neutron emission cross sections for n+56Fe reactions at incident energies of 7-13 MeV

The double-differential neutron emission cross sections for n+56Fe reactions at incident energies of 7-13 MeV at different angles are calculated by the UNF(abbreviation for unified,2009 Version)code,which is based on the unified Hauser-Feshbach and exciton model.The results indicate that the higher the incident energies,the better the results,although there are some discrepancies between the calculated results and the measured data for natural iron.These discrepancies are analyzed in detail in this paper.In addition,the calculated results are also compared with the evaluated results of ENDF/B VII.O and JEFF-3.1.1 near the angle of 90°at incident energies of 8.17 and 11.5 MeV,respectively.     

盐渍化土壤偏振高光谱信息与土壤线的关系初探

正确评价土壤盐渍化对地区农业生产与生态环境具有重要意义。土壤线对土壤盐渍化程度具有一定的指示作用,但在不同角度下观察获得的土壤光谱特征会发生变化,土壤线的参数值也会随之变化。依据以实验室测定的盐渍化土壤多角度偏振高光谱反射率,分析并确定土壤盐渍化程度与土壤线参数之间的关系,初步探求在偏振反射条件下土壤线最佳的获取方式。结果表明：(1)土壤光谱反射率随波段的增加逐步缓慢上升,趋于平缓。随着盐渍化程度的增强,土壤的光谱反射率先逐步降低至某一临界值后又逐步升高;(2)土壤的盐渍化程度与土壤线的斜率和截距均呈线性相关,随着盐渍化程度的增强,土壤线的斜率变小,截距变大;(3)探测天顶角影响偏振状态与土壤线参数的关系,当探测天顶角一定时,偏振状态与土壤线参数之间具有规律性。探测天顶角在0°-50°之间,随角度的变大,土壤线斜率变大,截距变小;(4)偏振状态影响土壤线参数与土壤盐渍化程度的相关性程度,初步确立偏振角度为90°,探测天顶角为25°状态下,建立的土壤盐渍化程度与土壤线参数关系模型较优。为定量反演土壤盐渍化程度提供新的途径。可以用于土壤的盐渍化程度评价。     

Standing Waves along a Microwave Generated Surface Wave Plasma

Two surface wave plasma columns, generated by microwave power in argon at gas pressures of 0.05 torr to 330 torr, interact in the same discharge tube to form standing surface waves. Radial electric field Er and azimuthal magnetic field H? outside the discharge tube are measured to be 90° out of phase with respect to axial position and to decay exponentially with radial distance from the tube axis. Maximum light emission occurs at the position of maximum H?, and minimum Er. Electron temperature and density are measured at low pressures with double probes inserted into the plasma at a null of Er. Measured electron densities compare well with those predicted by Gould-Trivelpiece (GT) surface wave theory. Measured electron temperatures are the same order of magnitude as temperatures predicted by positive column theory.     

基于近红外反射光谱的洋葱可溶性固体物检测

研究利用近红外(924～1 720 nm)反射光谱预测了洋葱的可溶性固体物含量。实验选取了三种不同产地和不同采收期的洋葱为样本(268)。在重复采集光谱数据之后,榨取对应光谱采集处洋葱块汁,测定可溶性固体物参考值。研究对比了Savitzky-Golay平滑、散射校正和微分处理等预处理方法,同时基于偏最小二乘回归方法建立了统计模型。结果表明,带S-G平滑的微分处理在平滑窗口为32,跨度为10时效果最佳。一阶微分比二阶微分的预处理效果要好,预测复相关系数R2为0.87,均方根误差RMSEP为2.42 °Brix。对比显示,无平滑处理光谱数据散射校正预处理得到的结果最好,预测复相关系数R2为0.88(RMSEP=2.31 °Brix)。采用交叉验证得到的PLSR模型预测复相关系数R2为0.90,RMSEP为1.84 °Brix,其相对分析误差RPD为3。说明加散射校正处理的近红外反射光谱可用于洋葱的可溶性固体物检测。     

夹持方式对频率转换KDP晶体面形的影响

针对惯性约束聚变（ICF）系统中大口径超薄KDP晶体在不同夹持和不同姿态下的面形变化,采用有限元分析软件ANSYS,建立了大口径超薄KDP晶体在不同夹持和不同姿态下的应变模型及其边界条件的确定方法,计算了四周简支正面点力、四周固支正面压条、四周简支侧面点力、四周固支侧面压条4种夹持方式在30°和垂直姿态下大口径超薄KDP晶体的面形变化,并给出了面形变化的P-V值和RMS值。在此基础上,通过对不同夹持和不同姿态下KDP晶体面形变化的分析和比较,给出了四周固支正面压条是引起晶体面形变化相对较小的夹持方式的结论。