单模光纤SBS阈值的研究

研究了阈值增益系数与光纤长度的关系,计算了受激布里渊散射的理论阈值。设计并搭建了受激布里渊散射阈值测量系统,在常温状态下对5km SMF28的受激布里渊散射阈值进行了测量,测得的阈值为7mW,这与受激布里渊散射的经典阈值估算模型计算所得的结果存在一定差异。研究其时域特性并分析了偏振态对受激布里渊散射的影响,得到实验系统修正后的阈值计算公式。     

标准盐度下水的受激布里渊散射阈值研究

从基本的耦合波方程出发,推导出受激布里渊散射公式,同时得出了可探测到的受激布里渊散射条件,以及间接可探测受激布里渊散射的阈值方法。采用测量激光射入不同长度样品产生SBS回波信号及透过介质激光能量强度的改变,并通过特定公式得出35‰的海水标准盐度下不同长度样品对激光的衰减情况。最后在项目所处条件下,验证了35‰海水标准盐度下受激布里渊散射阈值的存在。对受激布里渊散射阈值的产生进行了分析,并在与纯水中SBS阈值的对比中,得出了相同条件标准盐度下水的阈值较纯水中大的结果。     

近远红外自由空间光通信中的误码性能分析

利用光子追踪法建立了大气直视信道模型,仿真分析了信噪比(SNR)、比特率和能见度三者对自由空间光通信误码率的影响.选用1.55 μm和10.6μm两个波长作对比分析,结果显示两种波长的误码率随SNR的增大而减小,随比特率的增大而增大.在能见度较低时,10.6 μm激光的误码性能优于1.55 μm激光,并且在低SNR和高比特率的情况下,这种优势越发明显.在能见度较高时,两种波长的误码性能相差无几.     

双频Nd:YVO4微片激光器功率均衡研究

根据微片激光器工作温度、增益介质发射谱和谐 振波长三者的关系,研究了双频Nd:YVO₄微腔激光 器的功率均衡机制。在实验中,通过温控调节双频激光波长和发射谱的相对漂移,实现了双 频激光的相对 功率可调。实验结果表明,当激光器温度在2.5～22.5℃范围增加时 ,双频激光的右峰/左峰相对功率比从 6.471变化到0.028;当温控在9. 1℃时,双频 激光的相对功率比约为1.00∶1.00,实现了功率均衡;当温控在 7.5℃时,双频激光的相对功率比为1.89∶1.00,此时双频激光的功率乘积最大,可实现最高拍频效率。     

基于MPPC阵列探测器的激光测距系统与试验

将4×4多像素光子计数器(MPPC)阵列作为回波 探测器,利用云南天文台升级后的1.2m望远 镜分光路卫星激光测距(SLR)系统,开展了地面漫反射靶和AJISAI卫星的SLR试验。地面靶目 标是60cm的 Al塑板,光程约为45m,用示波器采集单通道输出信号与16通道合并 输出信号,合并输出信号幅值明 显高于单通道输出信号,表明不止一个通道有响应;用事件计时器记录主波、回波时刻并进 行距离解算, 其RMS约为21.7cm,与激光脉冲宽度、漫 反射目标的形状效应引起的测距误差相当。实验结果表明,阵列型探测器较单 元型有一定优势,实验中采用的MPPC阵列探测器进行性能升级后可用于SLR。     

The response of Arundo donax L. (C3) and Panicum virgatum (C4) to different stresses

In this work, two perennial rhizomatous grasses (Arundo donax L. (giant reed; C₃) and Panicum virgatum L. (switchgrass; C₄)) considered as promising energy crops have been subjected to four different types of stress in two experiments: (i) both species were subjected to four salinity and water stress treatments [well-watered with non-saline solution (WW S−), low-watered with non-saline solution (WS S-), well-watered with saline solution (WW S+) and low-watered with saline solution (WS S+)]; and (ii) both species were subjected to three temperature and light treatments [ambient temperature and light (C), ambient temperature and darkness (AD) and cold temperature and darkness (CD)]. Photosynthetic and physiological parameters as well as biomass production were measured in these plants. It can be hypothesized that a higher photosynthesis rate (A_sat) was be observed in switchgrass as a consequence of its C₄ metabolic pathway. However, our results indicated a similar A_sat at the beginning of the experiment for both species. This could be due to switchgrass being an NAD-ME C₄ type whereas giant reed has been reported as a C₃ species with a high photosynthetic rate. We showed that switchgrass seems to be more resistant to stresses such as water stress, salinity and cold than giant reed in our greenhouse conditions.     

Solar energy integration into advanced building design for meeting energy demand and environment problem

The dangerous effects of burning fossil fuels on global warming, alternative energy sources will become indeed important in the future. Because of fossil fuels energy sources shall run out by the early 22nd century given the present rate of consumption. Atmospheric concentration of greenhouse gases is trapping heat radiated from the Earth's surface, which cause global warming and environmental problems such as greenhouses effect, stratospheric ozone depletion, acid precipitation, and flooding of coastal settlements. This implies that sooner or later humanity will rely heavily on renewable energy sources. Here we have introduced light energy at an idealized large‐scale application to produce solar energy, where exterior skin and roof of buildings shall be at least 25% blackbody‐assisted photovoltaic to capture solar energy during the whole year. Simply, it is a calculative reaction of solar irradiance on innovative building design to capture sunlight most efficiently that would be the cutting edge technology for the ultimate solution of global energy, environment, and climate crisis. Copyright © 2016 John Wiley & Sons, Ltd.     

Label‐Free Imaging of Nanoparticle Uptake Competition in Single Cells by Hyperspectral Stimulated Raman Scattering

Imaging and quantification of nanoparticles in single cells in their most natural condition are expected to facilitate the biotechnological applications of nanoparticles and allow for better assessment of their biosafety risks. However, current imaging modalities either require tedious sample preparation or only apply to nanoparticles with specific physicochemical characteristics. Here, the emerging hyperspectral stimulated Raman scattering (SRS) microscopy, as a label‐free and nondestructive imaging method, is used for the first time to investigate the subcellular distribution of nanoparticles in the protozoan Tetrahymena thermophila. The two frequently studied nanoparticles, polyacrylate‐coated α‐Fe₂O₃ and TiO₂, are found to have different subcellular distribution pattern as a result of their dissimilar uptake routes. Significant uptake competition between these two types of nanoparticles is further discovered, which should be paid attention to in future bioapplications of nanoparticles. Overall, this study illustrates the great promise of hyperspectral SRS as an analytical imaging tool in nanobiotechnology and nanotoxicology.