Measurement of Optical Fiber Geometry Parameters with Bessel Function Fitting Method

Geometry parameters of optical fiber are crucial in evaluating the quality of the optical fiber.Near⁃field light distribution method is recommended in GB15972.20-2008 for the measurement of geometry parameters.To distinguish the boundary between fiber core and cladding,it is necessary to illuminate the fiber.The end face of the core is a bright spot with unclear edge,so the true edge of the core and the cladding cannot be accurately judged.A method is proposed in this paper to measure the geometry parameters of optical fiber by Bessel function fitting.Theoretically,the solution to the electromagnetic vector of mode field satisfies Bessel function,and the boundary between the core and the cladding can be precisely extracted by Bessel function fitting.Edges of the fiber were fitted by elliptical curves,and the geometry parameters of the fibers could be calculated.Results show that the maximum deviations of the diameters and the average differences of the fibers were decreased under normal and abnormal conditions respectively.The proposed method is an efficient way to obtain edge data and can improve the accuracy and stability of geometry parameters of optical fibers.

Bio-inspired optimization algorithms for optical parameter extraction of dielectric materials: A comparative study

Particle swarm optimization(PSO) and invasive weed optimization(IWO) algorithms are used for extracting the modeling parameters of materials useful for optics and photonics research community. These two bio-inspired algorithms are used here for the first time in this particular field to the best of our knowledge. The algorithms are used for modeling graphene oxide and the performances of the two are compared. Two objective functions are used for different boundary values. Root mean square(RMS) deviation is determined and compared.

Optical Dispersion Parameters with Different Orientations for SrLaAlO_4 Single Crystals

The different optical dispersion parameters of SrLaAIO4 single crystals have been studied by the transmission andreflection measurements at normal incidence for the three orientations 001, 100 and 101 in the spectral range400 nm^2500 nm.The optical absorption data revealed the existance of allowed indirect and direct transition. Therefractive index has abnormal behaviour in the spectral region 400~900 nm, but has a normal one in the higherwavelength region. The optical dispersion parameters, the single oscillator energy Eo and the dispersion energy Edwere determined and indicated the ionic structure of the material. The high-frequency dielectric constant, the latticedielectric constant and the electronic polarizability were determined by the free carriers and the lattice vibrationmodes. The real dielectric constant (?)1, the dielectric loss tangent (tanδ), the volume (VELF) and the surface energyloss function (SELF) have also been discussed.

Terahertz Spectroscopic Study of Standard Substances for Bituminous Coal and Anthracite

This study underscores the significance of online monitoring of standard substances for bituminous coal and anthracite,two commonly used fossil fuels.Terahertz technology emerges as a powerful non-destructive detection method capable of revealing the physical and chemical properties of measured objects.In this research,terahertz time-domain spectroscopy technology was employed to investigate the spectral characteristics of four distinct types of bituminous coal and anthracite samples.The refractive index and absorption coefficient spectra of these samples were calculated across a frequency range of 0.5 THz to 2.5 THz.Furthermore,principal component analysis was conducted using all refractive index and absorption coefficient data within this frequency band.Through the analysis and comparison with known parameters of coal standard materials,it was established that carbon content primarily influences the refractive index of bituminous coal and anthracite,while ash content predominantly affects the absorption effect.These findings underscore the potential of terahertz spectroscopy in conjunction with principal component analysis to qualitatively assess the similarities and differences between coal samples,thus offering novel insights for the online monitoring of diverse coal types and qualities.

Optics and Spectral Investigation in Dy^(3+)-Doped Borate Glasses

Dy^3＋-doped borate glasses （LBLB） with high effective visible fluorescence emission were synthesized. The absorption spectrum and fluorescence spectrum of this glass were measured and analyzed. By using J-O theory, the oscillator strengths for some absorption transitions were calculated according to the absorption spectra. The intensity parameters Ω1 （t = 2, 4, 6） of Dy^3＋ were determined by using a least-squares fitting approach, and the values are 4.04 × 10^-20, 1.30 × 10^-20 and 1.82 × 10^-20 cm, respectively. The root-mean-square deviation δrma was calculated. Under UV light excitation, Dy^3＋-doped borate glasses （LBLB） emit intense yellowish white lights. The excitation spectrum indicates that argon laser is the effective excitation source in Dy^3＋-doped LBLB glasses

Research on optical properties of cardiovascular tissues based on OCT data

As a high-resolution optical imaging technology,Optical Coherence Tomography(OCT)has been widely used in the diagnosis and treatment of cardiovascular diseases.It has played an important role in the detection and identification of atherosclerotic plaques and has significant advantages.In this paper,we realized to extract the optical characteristic parameters of the target sample based on the OCT data by establishing optical transmission models conforming to the OCT principle.The optical phantoms and coronary artery of domestic pig were used as research samples to study the difference between the optical properties of the cardiovascular tissues.It can provide a basic method for further study of optical characteristic parameters of atherosclerotic plaques,and also lay a foundation for realizing the quantitative evaluation of atherosclerotic plaques with multiple optical characteristic parameters in the future.

Perfect photon absorption based on the optical parametric process

The perfect photon absorption is studied in a cavity quantum electrodynamics(CQED) system, in which an optical parameter amplifier(OPA) is coupled to the cavity mode. This makes it possible to control the optical phase to realize the perfect photon absorption. It is found that in the presence of one and two injected fields, the perfect photon absorption is present in these two cases and can be controlled by adjusting the parametric phase. Moreover, different from the previous predictions of perfect photon absorption in atomic CQED systems, the perfect photon absorption can be changed significantly by the relative phase. Our work provides a new platform to use the parametric processes to make an available way to control the behaviors of photons and to take advantage of the optical phase to achieve the perfect photon absorption.

Synthesis and study the influence of yttrium doping on band structure,optical,non-linear optical and dielectric results for Ca_(12)Al_(14)O_(33) (C12A7) single crystals grown using traveling-solvent floating zone (TSFZ) method

Ca_(12)Al_(14)O_(33)(C12A7)and Y_(0.02)Ca_(11.98)Al_(14)O_(33)(Y-C12A7)single crystals were grown by using the traveling-solvent floating zone(TSFZ)method.The temperature was increased to avoid the bubbles and cracks which may be formed during the preparation of the ingot material.We have started with the flux higher than the normal to avoid the bubbles and make good treatment for the solid-liquid interface.The structures of both Ca_(12)Al_(14)O_(33)(C12A7)and Y_(0.02)Ca_(11.98)Al_(14)O_(33)(Y-C12A7)were studied by using x-ray diffraction(XRD).Optical properties for C12A7 and Y-C12A7 single crystals have been studied in order to determine the optical parameters such as optical energy gap(Eg),refractive index n,oscillating energy(Eo),dispersion energy(Ed),volume energy loss function(VELF),and surface energy loss function(SELF).Finally,a new result for these samples is that the third-order nonlinear optical susceptibility(χ(3))was determined.The results have been discussed with effect of Y-doping on the C12A7 single crystals for optical and industrial applications.

An investigation on the magneto-optic properties of terbium gallium garnet under high magnetic field

This paper reports that a series of Nd3＋：Er3＋：yb3＋ co-doped borosilicate glasses have been prepared and their absorption spectra measured. The J-O intensity parameters Ωk （k = 2, 4, 6）, spontaneous radiative lifetime Trad, spontaneous transition probability A, fluorescence branching ratio β and oscillator strength fed of the Nd3＋ ions at room temperature are calculated based on Judd-Ofelt （J-O） theory. The temperature dependence of the up-conversion photoluminescence characteristics in a Nd3＋：Er3＋：Yb3＋ co-doped sample is studied under a 978 nm semiconductor laser excitation, and the energy transfer mechanisms among Yb3＋, Er3＋ and Nd3＋ ions are analysed. The results show that the J-O intensity parameters Ω2 increase when the Nd3＋ concentration of the Nd3＋：Er3＋：yb3＋ co-doped borosilicate glasses increases. The possibility of spontaneous transition is small and lifetimes are long at levels of 4F5/2 and 4F3/2. The intensity of Nd3＋ emissions at 595, 691, 753, 813 and 887 nm axe markedly enhanced when the sample temperature exceeds 400 K. The reasons being the cooperation of the secondary sensitization from Era＋ to Nd3＋ and the contribution of a multi-phonon.

Numerical Analysis of the Analytical Relationships between Angstrom Coefficients of Aerosols and Their Optical Properties for Four Types of Aerosols

In this paper, the authors numerically analyzed the analytical relationships between angstrom coefficients and optical properties of aerosols to the existing data extracted from OPAC at the spectral length of 0.25 μm to 2.5 μm at eight relative humidity for desert, urban, marine clean and continental clean aerosols. That is apart from their relationships with the wavelength that was determined, in this paper their relation with respect to aerosols’ type and RHs are determined. The properties extracted are scattering, absorption, and extinction coefficients and single scattering albedo. The results showed that the extinction and single scattering albedo are correct for all the aerosols but single scattering co-albedo is satisfied for only sahara and continental clean.

从全波段太阳直射辐射确定大气气溶胶光学厚度 I：理论

本文提出了从全波段太阳直射辐射信息确定０．７μｍ波长大气柱气溶胶光学厚度的一种新方法。数值试验表明，对各类气溶胶谱分布，在水汽含量±０．２ｃｍ的误差、臭氧总量±０．１ｃｍ的误差、太阳直射辐射的±１％的观测误差以及太阳常数的±２％误差范围内，对小于０．１的０．７μｍ波长气溶胶光学厚度，它的解误差一般小于０．０１７，对大于０．１并小于０．６的光学厚度，它的解误差一般小１０％。

从宽带太阳直接辐射小时或日曝辐量反演气溶胶光学厚度研究

从宽带的太阳直接辐射1天或1小时累计量(曝辐量)气象观测资料反演气溶胶光学厚度的一个有效方法是很有用的。作者把太阳曝辐量与“等效”的瞬时太阳直接辐射关联起来,建立了一个与曝辐量“等效”的瞬时太阳直接辐射的模式;应用该模式和一个“等效”波长模式,发展了一个从太阳直接曝辐量反演气溶胶光学厚度的方法。作者还从试验上比较分析了由某时刻的宽带太阳直接辐射、每小时或1天的太阳直接辐射曝辐量反演得到的气溶胶光学厚度以及由太阳光度计探测的气溶胶光学厚度。试验结果表明,由日太阳直接辐射曝辐量反演得到的气溶胶光学厚度可理解为辐射加权的日平均光学厚度。

冰云短波辐射特性参数化

该文对卷云和高层云分别构造了１５种冰晶尺度分布，３种云高和云厚，总共３０种冰水含量、９０种冰水程长模式．对尺度小于与大于３０μｍ的冰晶粒子的单次散射特性分别用表面积等效冰球Ｍｉｅ理论和射线光学理论进行计算．采用ｄｅｌｔａ－Ｅｄｄｉｎｇｔｏｎ法计算了在４种不同地面反射率下冰云的多重散射辐射传输特性，提出了冰云辐射特性的参数化公式，指出参数化公式可以用于气候模式或大气环流模式．

云天地表总辐射和净辐射瞬时值的计算方法

为减少计算机时,满足实时预报要求,全球数值预报模式中的辐射计算频率通常设定为3 h。这样处理会大大减少计算量,但同时导致较大的辐射日变化偏差,并影响模式对地面能量平衡、对流及降水的模拟。为改进这一缺陷,建立了一种辐射快速计算方案,可用于计算瞬时地面太阳总辐射和净辐射,使到达地面的太阳辐射计算可与模式积分同步进行,改善地面太阳辐射日变化模拟。本文介绍云天情况下的总辐射和净辐射计算方案,该方案所用的输入变量均为预报模式或卫星观测提供。结果表明:该方案既可用于数值预报模式,也可利用观测资料独立计算地面太阳辐射。通过使用美国能源部大气辐射观测资料检验,证明该方案的精度高,地面总辐射瞬时值的平均计算误差小于7%。

卫星对地观测中大气与地表辐射贡献的参数化

卫星对地观测定量遥感地表与大气特性是当前地球科学与应用研究的关键手段之一。在定量遥感中区分大气和地表在地－气系统对空间散射辐射中各自的贡献与作用是关键的一步。这一问题的核心是基于辐射传输方程的数值计算建立起适合应用于遥感反演中分离大气与地表贡献的参数化表达式。本文对特定的气溶胶气候类型和可见／近红外波段建立起定量的表达形式，并对表达式的物理含义和拟合精度进行了分析。最后讨论了其应用的可行性和进一步的工作。

CsCl:Cr和CsBr:Cr的光谱和g因子的理论研究

文用参量化轨道理论和双自旋轨道耦合系数模型计算了掺Cr3+的CsCl和CsBr晶体的光谱和顺磁 g因子 。

导弹组合建模及电磁散射特征快速提取

该文将常规导弹目标分解为平板、圆柱、圆台和球冠等基本几何体散射单元,通过参数化组合建模、散射场解析计算和矢量场叠加的方法,快速仿真得到导弹目标的电磁散射数据,以支持其RCS、一维距离像和二维ISAR图像等电磁散射特征提取。计算结果表明,该方法基本能够满足目标电磁散射实时、高精度计算需求,开发的仿真软件为导弹目标基于方案验证需求的电磁散射特性快速计算与评估提供了有力支持。

基于纹理约束和参数化运动模型的光流估计

提出了一种基于局部小平面运动的光流估计新方法。目的是获得精确致密的光流估计结果。与以往采用亮度一致性区域作为假设平面的算法不同 ,本算法利用序列图像的纹理信息 ,在纹理分割区域的基础上 ,进行运动估计。该算法首先通过微分法计算粗光流 ,可以得到参数化光流模型的初始估计 ,然后通过区域迭代算法 ,调整初始估计 ,从而得到精细的平面分割及其对应的参数化光流模型。基于纹理信息的部分拟合算法被用于算法的每一步当中 ,保证了纹理边缘位置的光流估计值的准确性。实验采用了标准图像序列 ,结果表明 ,可以得到更为精细的光流估计结果 ,特别是对于那些有着丰富纹理信息的室外环境的图像序列 ,而且在运动边界处的结果改善尤为明显。

两种对流参数化方案对辐射能量收支的影响研究

利用中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室的格点大气环流模式(GAMIL)1.0版设计了两组数值模拟实验来研究两种不同的对流参数化方案对辐射能量收支的影响。这两种对流参数化方案分别是:Zhang and McFarlance/Hack方案(简称ZM)和Tiedtke/Nordeng方案(简称TN)。对应的数值模拟实验分别取名为EX_ZM和EX_TN。通过对实验结果的分析表明:在对流过程中,EX_ZM允许深对流和浅对流同时发生,因此两种对流同时在模式低层消耗了更多的水汽,释放了更多的潜热,引起了更大的增温;EX_TN每次只允许一种对流发生,也就避免了不同类型的对流在同一层同时消耗水汽的现象。因此对流过后,EX_ZM的环境空气相对湿度较小,而EX_TN周围空气的相对湿度较大,有利于低云云量的生成和大尺度的凝结,因此EX_TN模拟的低云云量偏多,低层的云水含量偏高,模式低层的云光学厚度偏大,这就使得EX_TN中更多的太阳短波辐射通量被云反射掉,严重低估了模式对短波波段的辐射通量的模拟。此外,不同的对流参数化方案通过改变云的长波发射率和降水,进而影响了模式对长波波段的辐射通量、感热和潜热通量的模拟。

ITO薄膜的透射谱解谱

用直流磁控溅射法在普通载波片上制备了厚度130nm左右的ITO薄膜,分别在100、200、300和400℃下退火1h。测量了退火前后几个样品的XRD和透射率,利用椭偏解谱方法对几个样品的透射谱进行建模及解谱,结果表明,未退火样品为非晶结构,退火后为多晶结构;退火温度在300℃以下的样品,随着退火温度的升高其n和k值都有明显的降低,退火温度为400℃的样品n和k值却有所增大。利用吸收系数得到了几个样品的直接带隙,其变化范围在3.7eV^3.9eV之间。