用双周期光纤光栅实现温度和应变的同时测量

介绍了光纤光栅传感器的一般原理，分析了长周期光纤光栅和Bragg光纤光栅的应变和温度响应机理。结果表明，长周期光纤光栅和Bragg光纤光栅的温度和应变灵敏度不仅与纤芯参数和光栅周期有关，还依赖于包层参数。在同一根光纤上先后写入长周期光纤光栅、Bragg光纤光栅，利用长周期光纤光栅和Bragg光纤光栅基模与包层模耦合时温度和应变灵敏度的不同，实现应变和温度的同时测量。     

光纤光栅的温度补偿

提出了一种简单、小型的光纤光栅温度补偿器件，将光纤光栅粘贴在具有负热膨胀系数的材料上，实现了光纤光栅的温度补偿。该器件在-20～44℃温度范围内光栅波长变化0.08m，是未补偿光纤光栅的1／8。     

用于ICF的光栅特性

针对透射光栅的减反射技术、ICF系统使用的多用途光栅的性质以及部分相干光在光栅中传输的特性等方面进行了详细的分析和模拟计算，较为系统的研究了用于ICF的光栅特性。针对透射光栅的表面反射不利因素，将光栅的工作角度设置到布儒斯特角附近，利用光束成布儒斯特角入射具有的特殊性质可以达到减反射的目的。计算结果显示，对长周期的透射光栅，将其设置到布儒斯特角附近工作能降低光栅的反射率，特别是总反射率可以明显降低。ICF系统中的色分离光栅可以考虑试用这种方案减反射；对周期在波长附近的短周期光栅也能实现减反射，并能保证更高的一级衍射效率，但布儒斯特角的设置使得TM入射波的一级衍射效率的极值出现在光栅刻槽深度为102的地方，相对TE波，其深度周期被大大推迟，在实际应用中应综合考虑。     

氮化硅片上光栅耦合器的优化和实验

在785 nm激励的拉曼片上传感器结构中，氮化硅片上光栅耦合器的性能直接关系到激励光的耦合效果。首先建立了光栅耦合器的二维、三维结构模型，采用时域有限差分（FDTD）仿真软件对光栅耦合器进行数值分析。以耦合效率为主要性能指标，分析了光源入射角度、光栅常数、光栅高度、填充因子和光栅刻蚀深度各参数的影响。采用电子束光刻法制备了光栅耦合器。最后，对三维全刻蚀聚焦波导光栅耦合器进行了测试。结果表明，二维波导光栅耦合器的性能最好，其耦合效率可达39.64%，三维全刻蚀聚焦波导光栅耦合器在实际测试中的耦合效率能达19.91%。光栅耦合器能有效将光耦合进波导中，在波导传感中具有潜在的应用。     

透射光栅衍射率的实验标定和数值计算

简要介绍了实验室中使用的三种透射光栅的结构，在北京同步辐射源上实验标定了这些光栅的相对衍射效率。借助于光栅模型，得到了光栅的重要结构参数，并对光栅的绝对衍射效率进行模拟计算和讨论。     

低串扰的多波长光纤光栅色散补偿器

分析了光纤光栅色散补偿系统中的串扰，并比较了几种常用的多波长光纤光栅色散补偿器的串扰特性，结合串联的窄带光纤光栅和取样光纤光栅的优点，提出一种抑制光纤光栅色散补偿系统串扰的方法.它通过在邻近信道间引入随机时延差，既能改善取样光纤光栅的线性串扰特性，又能抑制交叉相位调制效应和四波混频等非线性串扰.使用该方法可以得到具有低串扰的多波长光纤光栅色散补偿器.     

基于泰伯效应的高斯光束尺寸测量

光栅用在高斯光束参数测量中的突出优点是方法简单，成本较低，全息光栅由于其制备容易，无周期误差而比一般光栅具有更多的优点。在用光栅进行光斑测量的实验中，观察到由全息光栅引起的泰伯（Ｔａｌｂｏｔ）效应携带有关光斑参数的有用信息，本文提出了一种基于泰伯效应的测量方法，只需测定条纹间隔就能确定高斯光束尺寸，因此降低了对光源或光栅定位精度，电路和光源稳定性的要求，文中聚焦高斯光束照明全息光栅时光场分布，及其     

光纤光栅激光器激射波长的研究

一般认为，用光纤光栅作选频元件的光纤激光器，激射波长与光纤光栅中心反射波长一致，本文报道了不同的实验研究结果。通过细致的实验研究，发现光纤光栅激光器激射波长相对于光纤光栅中心反射波长有一定的偏移。激射波长可以出现在光栅中心反射波长的长波端，也可以出现在其短波端。对不同腔结构的掺镱、掺铒光纤光栅激光器的深入研究证明，谐振腔的各向异性对激光器的激射波长偏移起到决定性的作用，波长最大偏移量主要受限于光纤光栅的反射带宽。通过激光腔内的偏振控制器改变谐振腔的各向异性，可以在光纤光栅的反射带宽内控制激射波长的位置。     

窄带光纤光栅的写入

改进相位掩模法写入光栅的装置，提高其机械稳定性和温度稳定性，不仅提高了光纤光栅的反射率，而且降低了带宽，特别是能在国产的光敏光纤上写出了大于９９％反射率和小于０２ｎｍ带宽的高质量的光纤光栅这种光栅特别适用于光纤光栅传感方面的应用     

横向衍射技术测量光纤光栅的特性

提出了一种用Ｈｅ－Ｎｅ激光侧面照射光纤光栅，从另一侧探测光栅的布拉格衍射效率来测量光纤光栅光谱特性的技术，并用该技术测量了光栅的折射率变化的分布。     

基于有限立体角测量的多光谱测温

辐射测温以Planck定律为基础通过测量物体表面的发射辐射来反演温度。推导了有限立体角辐射测量条件下的单色测温方程,发现多光谱辐射测温能够实现温度和光谱发射率同时求解通常需满足特定的辐射测量条件：进行微元立体角辐射测量或仅针对漫发射体的有限立体角辐射测量。引入多项式发射率模型,经过数学转化,可以摆脱以上测量限制,得到具有测量普适性的单色测温方程,但却不一定能同时测量光谱发射率。对测温方程组的多解问题进行了初步研究,提出使测量通道数大于待求变量数及采用非线性最小二乘来解决此问题。     

On the Physical Reality of Quantum Waves

The main interpretations of the quantum-mechanical wave function are presented emphasizing how they can be divided into two ensembles: The ones that deny and the other ones that attribute a form of reality to quantum waves. It is also shown why these waves cannot be classical and must be submitted to the restriction of the complementarity principle. Applying the concept of smooth complementarity, it is shown that there can be no reason to attribute reality only to the events and not to the wave or to the initial state of a given system. Thereafter, an experiment proposed by the authors is presented, where it is shown that the wave-like behaviour allows predictions that are not allowed on the grounds of a particle-like behaviour. In conclusion, we upheld that quantum waves must be real even if they do not belong to the same ontological level of events, which connected with particle detections.Institute of Philosophy, University of Urbino, Urbino 610 29, Italy; tarizzi@uniurb.it     

Entanglement and Non-Locality in Quantum Protocols with Identical Particles

We study the role of entanglement and non-locality in quantum protocols that make use of systems of identical particles. Unlike in the case of distinguishable particles, the notions of entanglement and non-locality for systems whose constituents cannot be distinguished and singly addressed are still debated. We clarify why the only approach that avoids incongruities and paradoxes is the one based on the second quantization formalism, whereby it is the entanglement of the modes that can be populated by the particles that really matters and not the particles themselves. Indeed, by means of a metrological and of a teleportation protocol, we show that inconsistencies arise in formulations that force entanglement and non-locality to be properties of the identical particles rather than of the modes they can occupy. The reason resides in the fact that orthogonal modes can always be addressed while identical particles cannot.     

Light harvesting with metasurfaces: applications to sensors and energy generation

Metasurfaces have been receiving increasing interest due to the complex array of radiation controlling properties that are possible with single-layer films. This talk and work will focus on metasurfaces that can provide light filtering according to wavelength, polarization, and other properties of an incident beam, and applied to a variety of sensors. Also, metasurfaces that exhibit light trapping and localization that can be used for energy generation will be described. One last group of metasurfaces will be discussed that display complex dispersion curves that exhibit fast- and slow-light properties that can be used to study the complex electromagnetic phenomena.     

The aging adult voice

Advancing age produces physiologic changes that may alter voice. Some of these changes are inevitable; others may be avoidable or reversible. In addition, many treatable medical conditions may cause voice changes similar to those of aging. It is essential that all voice care providers be familiar with the expected changes of aging, and be alert to reversible conditions that may adversely affect phonation and be mistaken for presbyphonia.     

北京SARS疫情走势的模型分析与预测

北京SARS疫情的公布数据表明，4月下旬以来，确诊病例的相对增加率随累计确诊病例数的增加而下降．假设这是一个线性关系，并且一直持续下去，我们发现疫情走势是一个反转的Fermi-Dirac分布，根据现有的公布数据可以预期北京平均每日新增病例数将在5月中旬下降到50人以下，在5月下旬下降到10人以下，在6月上旬下降到1人左右，疫情可望在6月中得到控制，最后的累计病例总数约为3千人左右。     

Principle of temperature,velocity and pressure of upper atmospheric wind measurement for the Voigt profile

Using the accurate expression of the Fourier transform of the pure Voigt spectral line profile, we present the principle of the passive optical method to measure temperature, velocity, and pressure of atmospheric wind for the Voigt profile. Through discussion, from the Gaussian, Lorentzian and Voigt profiles, we find that velocity will not be affected, pressure can be derived for Lorentzian and Voigt profiles, and temperature will be affected greatly. By simulation and comparison, we find that temperature derived from the Voigt profile is greater than that from the Gaussian profile, and it is less than that from the Lorentzian profile. This discussion will be significant in accurate upper atmospheric wind measurement.     

Multiparty Quantum Cryptographic Protocol

We propose a multiparty quantum cryptographic protocol. Unitary operators applied by Bob and Charlie, on their respective qubits of a tripartite entangled state encoding a classical symbol that can be decoded at Alice＇s end with the help of a decoding matrix. Eve＇s presence can be detected by the disturbance of the decoding matrix. Our protocol is secure against intercept resend attacks. Furthermore, it is eifficient and deterministic in the sense that two classical bits can be transferred per entangled pair of qubits. It is worth mentioning that in this protocol, the same symbol can be used for key distribution and Eve＇s detection that enhances the etfficiency of the protocol.     

Some theoretical and experimental aspects of the tachyon problem

In this paper, the hypothetical existence of tachyons is re-examined. It has previously been doubted whether tachyons would exist, for it can be shown with the space-time diagram used in the Special Theory of Relativity that they are moving backward in time for some moving systems, and this would contradict the principle of causality. Some scientists tried to save the tachyon theory by using the so-called reinterpretation principle, but it is considered that this can be easily refuted. This paper shows that it can be concluded from the Einstein-Planck frequency relation and the de Broglie wave equation that the absolute value of the mass of the tachyons must be much lower than the rest mass of the electrons-nearly zero. But that means that they do not have any measurable energy if they move with a finite value aboutc. But if tachyons withv>c cannot be measured they cannot cause causality paradoxes. The low mass of the tachyons has also consequences for experimental search, and it will be shown that the previous search was doomed to failure. The limits of the photo-production cross-section for tachyons in lead can be given as 1.5·10^?32?σ<7·10^?31 cm². Further, it can be shown that the kinetic energy of the tachyons is identical to their total energy. We see that tachyons cannot be regarded as ‘faster than light particles’ — they are more a new kind of luxons. If they were to be uncharged it would be nearly impossible to distinguish them from this class of particles.     

Nematic universality

In this work we will present theoretical arguments that explain why the nematic phase exhibits a universal behavior encompassing its entire range. By considering that the physical properties of the nematic molecules can be written as a product of two distinct terms, being the first a compound dependent term and the another a function characterizing the nematic phase, it will be shown that it is possible to remove from the experimental data the particularities characterizing an specific compound and a universal behavior is obtained. Furthermore, it will be shown that these universalities should be a direct consequence of a more fundamental universality, the universal geometrical shape of the nematic molecules.