YNbO4：Tm3+/Yb3+上转换发光特性研究

按照50Nb₂O₅-（46-x）Y₂O₃-4Yb₂O₃-xTm₂O₃（x=0.1,0.2,0.5,1,2）的配比方式,采用高温固相法制备出了掺杂Tm³⁺/Yb³⁺的YNbO₄晶体粉末。在980 nm红外光激发下,观测到波长为478,645,707 nm的上转换荧光,分别对应于Tm³⁺离子的¹G₄→³H₆、¹G₄→³F₄、³F₃→³H₆能级跃迁过程。利用上转换发射功率与980 nm激光器工作电流关系估算出跃迁过程吸收光子数目为2.72,2.69,2.01,从而确定出前两者为三光子吸收过程,最后一个对应于双光子吸收过程。运用Judd-Ofelt理论研究样品光谱特性,根据样品的吸收谱得到样品的谱线强度参数Ω_t（t=2,4,6）,进而得出理论振子强度及实验振子强度,二者均方根偏差δ_rms=1.299×10^-7。计算了Tm³⁺离子向下能级跃迁的跃迁几率、跃迁分支比等参数。最后得出结论：（1）³F₄能级寿命较长,适合作为上转换中间能级;（2）³H₅能级寿命较长,且³H₅→³H₆跃迁分支比（96.46%）接近100%,可用于产生1 216 nm激光。     

Correlation between Si diffusion and Si-induced disordering in AlGaAs/GaAs superlattices

Compositional disordering of AlGaAs superlattices induced by Si ion implantation and subsequent annealing has been studied by secondary ion mass spectrometry (SIMS). Distinct correlation is found between the induced disordering and the rapid Si diffusion which occurs above the critical concentration of about 3×10¹⁸ cm⁻³. The annealing-condition dependence of the disordering suggests that AlGa intermixing is induced by the vacancy flow enhanced by the Si_IIISi_V pair movement which causes the rapid Si diffusion. SIMS depth profiles of the heat treated superlattices co-doped with Si and Be do not show any appreciable Si diffusion and induced disordering. This is well-explained by the formation of SiBe pairs which prevents that of Si_IIISi_V pairs.     

Infrared problem in QED and electric charge renormalization

The electric charge renormalization in quantum electrodynamics is discussed, by taking into account the fact that an “infrared dressing transformation” is needed to go from the local states occurring in the Green's functions, to the (physical) charged states which obey Gauss' law. Apparent difficulties discussed in the literature are resolved. The construction of physical multicharged states is discussed explicitly.     

基于FP微阵列的压缩感知光谱重建研究

针对现有星载扫描光谱成像中无法同时实现高通量、高光谱分辨率的问题,提出采用法布里珀罗( FP)微阵列与压缩感知光谱成像方法.该方法通过在成像探测器前加FP微阵列, FP微阵列调制器每一单元对应不同高度,进而对输入光信号进行调制得到不同的光谱响应.结合扫描和压缩感知复原算法,最终获得高光谱图像数据立方体.该系统光谱范围为...     

Experimental and theoretical studies of the evolution of normal spectral emissivity during successive steps of tungsten oxidation

We studied the influence of oxidation on the normal spectral emissivity of tungsten in the wavelength range 1–10 μm under well-controlled conditions. The optical measurements have been performed under an oxygen pressure of 1.3 Pa and in the temperature range 800–1000 K, until the oxide was thick enough to be opaque to the radiation concerned. The experimental curves of emissivity versus exposure show an induction time followed by a maximum before a steady-state value is reached. In conjunction with a growth model, supported by X-ray diffraction and electron microscopy studies, we propose an optical model of heterogeneous media which correctly accounts for the observed variations of emissivity during the whole reaction. By inserting the optical constants of the various media into this model, we show that it is possible to characterize, by emissivity the morphology of the oxide on the surface during the reaction, until the oxide is thick enough to be opaque.     

基于PDMS薄膜的等离子体光栅仿真分析

为了实现对等离子体光栅共振波长的测量,研究光栅参数对应力的响应敏感程度,提出了一种新型的应力敏感型聚二甲基硅氧烷(polydimethylsiloxane,PDMS)薄膜等离子体光栅.基于时域有限差分(finite difference time domain,FDTD)法的原理,构造了一种结构仿真模型,即周期性等离子...     

Energy gap of some alkaline halate crystals by optical methods

Applying four optical methods i.e. Faraday rotation, optical absorption, diffuse reflection and refractive index dispersion the energy gap was calculated for LiIO₃, NaBrO₃ and NaClO₃ crystals. Preliminary discussion of electronic band structure of the crystals studied is given.     

保偏光纤和偏振器对传输光光谱的影响

保偏光纤和偏振器的参数以及它们之间的连接角度对传输光的光谱特性有重要的影响。利用琼斯矩阵建立了光波的传输模型,首次讨论了光波偏振度、光纤长度、光纤之间以及光纤与器件之间的对轴角度等对输出光谱的影响。研究表明,当光纤之间或光纤与器件之间的对轴角度不为零时,完全非偏振光的输出光谱形状不会发生改变,而偏振或部分偏振光波的输出光谱中叠加了周期函数。对轴角度一定时,光纤越长,周期函数的周期越小;光纤长度一定时,在一定的范围内,对轴角度越大,周期函数的幅值越大。通过实验对结论进行了验证。结论对采用保偏光纤和偏振器的系统具有理论指导意义。     

A combinative technique to recognise and discriminate turquoise stone

This study attempts to identify and categorize turquoise stone based on its compounds and major factors that introduces its color change. Turquoise samples which are investigated in this study have been collected from the most important turquoise mines in world. Combination of two different analysis methods assists this study for scrutinizing turquoise constituents and effects of their percent on its color change. The application of infrared spectroscopy and X-Ray Fluorescence (XRF) methods can reveal the true composition of various “turquoise” samples in range of blue color to green color. Whereas the first technique (FTIR) is especially capable in diff ;erentiating between natural samples and fake or simulant stones for prevent of jobbery. Changing percent of four compounds including CuO, Al₂O₃, P₂O₅ and Fe₂O₃, is the most effective factors of varying color in turquoise stones. In conclusion, blue turquoise stone contains great percent of light elements or blue color factors in comparison to green turquoise stone which contains jorum of heavy element.     

Amplification of Lipid Peroxidation by Regulating Cell Membrane Unsaturation To Enhance Chemodynamic Therapy

Lipid peroxidation (LPO) is one of the most damaging processes in chemodynamic therapy (CDT). Although it is well known that polyunsaturated fatty acids (PUFAs) are much more susceptible than saturated or monounsaturated ones to LPO, there is no study exploring the effect of cell membrane unsaturation degree on CDT. Here, we report a self-reinforcing CDT agent (denoted as OA@Fe-SAC@EM NPs), consisting of oleanolic acid (OA)-loaded iron single-atom catalyst (Fe-SAC)-embedded hollow carbon nanospheres encapsulated by an erythrocyte membrane (EM), which promotes LPO to improve chemodynamic efficacy via modulating the degree of membrane unsaturation. Upon uptake of OA@Fe-SAC@EM NPs by cancer cells, Fe-SAC-catalyzed conversion of endogenous hydrogen peroxide into hydroxyl radicals, in addition to initiating the chemodynamic therapeutic process, causes the dissociation of the EM shell and the ensuing release of OA that can enrich cellular membranes with PUFAs, enabling LPO amplification-enhanced CDT.