硅基二维光子晶体耦合器理论研究

光子晶体是一种具有光子带隙的新型人工材料,利用其具有控制和限制光子运动的特性可以制成新颖的光学器件。利用硅基二维光子晶体,提出了一种4端口耦合器。采用时域有限差分法作为研究工具,TM模作为研究对象,从理论上分析了这种器件的特性。在不同的耦合长度下研究光在输出端的功率透射率。结果表明选择适当的耦合长度可以使光在器件中呈现不同的状态。进一步研究表明,通过改变器件内部介质柱的半径,可以改变光在输出端的输出功率。从而证实了这种器件不仅具有波长选择性,而且具有潜在的可调节性,这些特性使得这种器件在全光开关的应用上具有潜在的优势。     

W掺杂ZnO电子结构与光学性质第一性原理计算

采用了基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法,计算本征ZnO和不同W掺杂浓度下W:ZnO体系的电子结构和光学性质.计算结果表明:W掺杂可以提高ZnO的载流子浓度,从而改善ZnO的导电性.掺杂后,吸收光谱发生红移现象,且光学性质变化集中在低能量区,而高能量区的光学性质没有太大变化,计算结果与相关实验结果相符合.最后,结合电子结构定性分析了光学性质的变化.     

Phantom validation and in vivo application of an inversion procedure for retrieving the optical properties of diffusive layered media from time-resolved reflectance measurements

An experimental validation of an inversion procedure for retrieving the optical properties of layered media from multidistance time-resolved reflectance measurements is presented. The results cover a wide range of optical properties, showing excellent effectiveness and reliability of the procedure in reconstructing the optical properties of a two-layered medium. The optical properties of the first layer and the absorption of the second layer could be retrieved with excellent precision, whereas the reduced scattering coefficient of the second layer was reconstructed with a large error. The first layer thickness could be retrieved with an error less than 50%. An example of retrieval of the optical properties of muscle from in vivo measurements during an arterial occlusion is shown.     

Optical properties of two-dimensional perovskites

The optical properties of two-dimensional (2D) perovskites recently receive numerous research focus thanks to the strong quantum and dielectric confinement effects. In addition to the strong excitonic effect at room temperature, 2D perovskites also have appealing features that their optical properties can be flexibly tuned by alternating organic or inorganic layers. Particularly, 2D chiral perovskites and 2D perovskites based heterostructures are emerging as new platforms to extend their functionalities. To optimize performance of 2D perovskites-based optoelectronic devices, it is critical to understand the fundamentals and explore the strategies to engineer their optical properties. This review begins with an introduction to the excitons and self-trapped excitons of 2D perovskites. Subsequently, inorganic/organic layer effects on optical properties and 2D perovskites based heterostructures are discussed. We also discussed the nonlinear optical properties of 2D perovskite. We are looking forward to that this review can stimulate more efforts to understand and optimize the optical properties of 2D perovskites.     

Optical properties of normal and thermally coagulated chicken liver tissue measured ex-vivo with diffuse reflectance

The purpose of the present study is to determine the optical properties of normal and thermally coagulated chicken liver at 720, 740, 770, 810, 825 and 840 nm wavelengths of laser irradiation. So, we were able to evaluate these optical properties (absorption and scattering coefficients) with ex-vivo study using Kubelka Munk Model (KMM) from the radial dependence of the diffuse reflectance with femtosecond pulsed laser in near IR region. These coefficients were significantly increased with coagulation. The penetration depths of the diffused light have been reported to a maximum value of 8.12 ± 0.36 mm in normal liver and 2.49 ± 0.17 mm in coagulated liver at 840 nm showing increasing behavior towards IR region. The Monte Carlo simulation was used to check the theoretical validation of measured optical properties of the tissue that showed a good match with our experimental results. We believe that these differences in optical properties will be helpful for the understanding arid optimal use of laser applications in medicine and differential diagnosis of tissues by using different optical methods. Especially for the investigation of biological tissue for photodynamic therapy (PDT), the knowledge of the specific optical properties and their thermo-induced changes is important.     

High Reflection Ge_(0.45)Te_(0.55) Recording Films

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纳米二氧化钒薄膜的电学与光学相变特性

采用双离子束溅射氧化钒薄膜附加热处理的方式制备了纳米二氧化钒薄膜。在热驱动方式下,分别利用四探针测试技术和傅里叶变换红外光谱技术对纳米二氧化钒薄膜的电学与光学半导体-金属相变特性进行了测试与分析。实验结果表明,电学相变特性与光学相变特性之间存在明显的偏差,电学相变温度为63 ℃,高于光学相变温度,60 ℃;电学相变持续的温度宽度较光学相变持续温度宽度宽;在红外光波段,随着波长的增加,纳米二氧化钒薄膜的光学相变温度逐渐增大,由半导体相向金属相转变的初始温度逐渐升高,相变持续的温度宽度变窄。在红外光波段,纳米二氧化钒薄膜的光学相变特性可以通过光波波长进行调控,电学相变特性更适合表征纳米VO₂薄膜的半导体-金属相变特性。     

有效介质近似在Cu-MgF2复合纳米颗粒薄膜光学性质中的适用性研究

采用射频磁控共溅射技术制备了Cu体积分数分别为15%和30%的Cu-MgF2复合纳米颗粒薄膜。透射电镜形貌图像表明,薄膜由不同形状的Cu晶态纳米微粒镶嵌于主要为非晶态的MgF2陶瓷基体中构成。用椭偏光谱技术计算得到Cu-MgF2复合薄膜在270~830 nm波段的光学常数谱。用考虑颗粒形状效应的有效介质近似计算得到Cu-MgF2复合薄膜在相同波段的光学常数谱。把两样品的透射电镜形貌图像与光学常数理论谱、实验谱相结合,分析讨论了Cu-MgF2复合薄膜的光学特性。结果表明:去极化因子取值0.33的麦克斯韦噶尼特(Maxwell-Garnett)模型可以较好地解释Cu体积分数为15%的Cu-MgF2复合薄膜的光学性质,而去极化因子取值0.6的布鲁格曼(Bruggeman)模型可以较好地解释Cu体积分数为30%的Cu-MgF2复合薄膜的光学性质。     

Origin of the optical contrast in phase-change materials

Several chalcogenide alloys exhibit a pronounced contrast between the optical absorption in the metastable rocksalt and in the amorphous phase. This phenomenon is the basis for their application in optical data storage. Here we present ab initio calculations of the optical properties of GeTe and Ge1Sb2Te4 in the two phases. The analysis of our computations and experimental data reveal the correlation between local structural changes and optical properties as well as the origin of the optical contrast in these materials. We find that the change in optical properties cannot be attributed to a smearing of transition energies as commonly assumed for amorphous semiconductors: the optical contrast between the two phases can only be explained by significant changes in the transition matrix elements.     

激光位移传感器的光学系统设计

针对目前国内自主研制的激光位移传感器精度低,测量范围小等问题,提出了一种采用光学设计软件预先仿真整个激光位移传感器光学系统的方法。在分析系统各部分的光学特性的基础上,结合具体要求设计了一个激光位移传感器的光学系统,其工作范围为（50±10）mm。采用系统分割的方法,将整个光学系统分为两部分进行设计,第一部分是激光束的整形透镜,要求在有效的工作范围内得到小而均匀的出射光斑,设计结果表明,在测量范围内,光斑大小能够控制在10-1mm量级;另一部分是被测面散射光接收的成像物镜,该系统的特点是物面和像面相对于光轴都有一定的角度,实验结果表明其成像满足Scbeimpflug条件。     

Z-Scan and Absorption Study of Crocin and Rhodamine B Decolorization by Bacterial Laccase

Dye decolorization is currently measured by the reduction of dye absorption, based on its linear optical properties in solution. However, this method is not suitable for high dye concentrations with linear attributes in the absorption spectra. In this work, nonlinear optical properties are used to study dye decolorization of Crocin and Rhodamine B treated with a bacterial laccase. For this purpose, the Z-scan was used to obtain the nonlinear refractive indices and nonlinear absorption coefficient of Rhodamine B and Crocin in the presence and absence of the bacterial laccase enzyme. The results showed that nonlinear optical properties could be used to study dye decolorization in solutions.     

不同浓度Ag掺杂ZnO电子结构和光学性质的第一性原理研究

基于密度泛函理论框架下的第一性原理计算方法,研究了不同浓度Ag掺杂ZnO体系的电子结构和光学性质。计算结果表明,不同浓度Ag原子代替Zn原子后会导致电子结构和光学性质有显著的改变,能带随掺杂浓度的增大带隙渐渐变窄,光吸收、反射等也随银掺杂浓度的增大先是向高能端偏移再向低能端移动。这暗示Ag掺杂ZnO对其电子结构及光学性质有很大的影响,为进一步研究掺杂对ZnO性质的影响提供理论基础。     

温度对生物组织模拟液光学特性影响的研究

采用牛奶作为生物组织的模拟液,研究温度变化对生物组织光学特性的影响。应用双积分球技术对牛奶在光波波长为1100~1700 nm、温度25~40℃范围内的光学参量进行了测量,分析光学参量随温度的变化规律。结果表明,温度对散射作用的影响比吸收作用更大,随温度的升高,约化散射系数具有明显减小的趋势。与25℃相比,40℃下的约化散射系数下降了约10%;而吸收率的变化趋势不明显且规律复杂。以上研究结果与公开发表的人体离体皮肤组织光学参量随温度变化的研究结果基本一致,从而为深入研究温度对生物组织光学测量的影响提供了理论和实践上的指导。     

Theoretical insight into the substituent effects on linear and nonlinear optical properties of azobenzene‐based chromophores

The linear and nonlinear optical properties of 4 kinds of experimental synthesized azobenzene‐based chromophores were investigated by different density functional theories (DFTs) upon the electronic structures. The structure‐property relationship was studied on each single molecule either in the gas phase or in diethylether and tetrahydrofuran (THF) solutions. The substituent effect on optical properties was revealed by checking the positions of substituent groups, and the influence of dynamic perturbation to the optical nonlinearity was investigated by simulating the experimental excitation. The results revealed that the substituent in the meta‐position of the azobenzene group affects the optical properties more significantly than that in the ortho‐position, which is in agreement with the experimental finding. The modulation of molecular hyperpolarizability of bridge‐substituted azobenzene derived by dynamic perturbation is not recommended because of the reduced dynamic hyperpolarizability relative to the static one. The different functions of the DFT method hardly affect the calculated results, while solvent effects of diethylether and THF solutions are significant on the optical properties, especially for optical nonlinearity. The information derived from the single chromophore may be helpful in the design and preparation of high‐performance nonlinear optical materials in further.     

The study of the optical properties of the GaAs with point defects

GaAs is a common material for negative electron affinity photoelectric cathodes. It has a widely application in night vision. It is unavoidable to produce point defects in the process of the GaAs growth. In this article, the first principle method is used to calculate the formation energy and the optical properties of six types familiar point defects in GaAs. Three types of point defects (Ga vacancy defect, As antisite defect and As interstitial defect) are easier to be formed in these six types according to the formation energy calculation. In fact, crystal GaAs is grown in an As-rich environment. The Ga vacancy, As antisite and As interstitial defects are easier to be formed in reality. Hence the theoretical calculation results are in keeping with the experiments. In this article, the optical properties of these three types are compared with that of perfect GaAs. The electron structures are changed as a result of the point defects. Some of the defect levels enter into the band gap and the electron transitions become easier. It makes the optical spectra move to the low-energy region. Additionally, GaAs with Ga vacancy defect and that with As interstitial defect shows similar optical properties. Therefore both of the two types of defects can be considered as the same in the later experiments. The theoretical results in this article provide the basis for experimental study for photoelectric emission of the real GaAs material related to the optical properties and electronic structures.     

The influence of optical properties of paints and coatings on the efficiency of infrared nondestructive testing applied to aluminum aircraft structures

IR NDT (Infrared Nondestructive Testing) is a popular method for detecting defects in composite, ceramic, and metallic structures. The effectiveness of IR NDT depends on various thermal and optical properties of the material being tested. The thermal properties, including thermal conductivity, thermal diffusivity, specific heat and density are important and have been discussed extensively in many treatises on IR NDT. However the optical properties of the surface are equally important and while the thermal properties cannot be changed, sometimes the optical properties can be.Bare metal surfaces have high reflectivities and low emissivities, and as a result, they are generally not good candidates for IR NDT. Painted, coated, anodized, and oxidized metal surfaces can, in some cases, be successfully tested with IR NDT, but the effectiveness depends on the optical properties of the surface. It is well known by IR NDT practitioners that the easy solution to the testing of reflective materials is to paint the surface black. However, this is not always practical and it may not be permitted by the “owner” of the part.This paper demonstrates a process of analyzing the interaction of spectral curves that are relevant to the IR NDT process. This process can be used to evaluate the effectiveness of an IR NDT process for use on real parts with specific coatings and can help select a coating that may improve the effectiveness. This paper shows examples of optical properties for some typical paints and coatings that may be used on aluminum aircraft structures. It shows the spectrum of a generic incandescent radiant heat source and how the energy from this source is absorbed by several of these paints. Further, it shows the interaction between an IR camera detector response curve and the other curves. And finally, it shows how these three can be combined to produce an “IR NDT” efficiency rating for several examples.     

Spectral study of the properties of photochromic polysubstituted lactones

The spectral and photothermal properties of thermally irreversible derivatives of dihetarylethenes, lactones, whose open form shows fluorescence, are studied. It is shown that the nature of substituents determines not only the absorptive but also the luminescent properties of these compounds, as well as their photocoloration and fluorescence quantum yields. The obtained dependences of the properties of lactones on their structure are important for targeted synthesis of compounds that can be used in the creation of two-photon reversible recording media with fluorescence reading of optical information suitable for application in 3D optical memory on optical disks.     

The estimation of a unique solution for steady-state diffuse optical tomography by applying mechanical pressure

The accuracy of diffuse optical tomography (DOT) highly depends on two important factors: first, the knowledge of the tissue optical heterogeneities for accurate modeling of light propagation, and second, the uniqueness of reconstructed values of optical properties. Previous studies illustrated that the inverse problem associated with steady-state DOT does not have unique solutions. In this study, we propose a simple method that can be applied to improve this challenging problem of steady-state DOT. In this method, we study the propagation of photons through compressed breast phantoms. The applied mechanical pressure can change the values of optical properties and this pressure dependence of optical properties as a set of constraint equations can be used to improve the inverse problem. The applied pressure can help us to restrict the distribution of possible values of depth and radius of defect inside breast phantom reconstructed by inverse problem.     

Effects of quantum confined stark effect and well thickness on optical properties of double quantum wells violet InGaN laser diodes

The effects of quantum confined stark effect (QCSE) and quantum well (QW) thickness on the optical properties of violet InGaN laser diodes (LDs) have numerically been investigated. The simulation results indicated that the QCSE greatly effects the optical properties of LDs, where QCSE relates to the QW thickness and it increases when the QW thickness is wider which leads to deteriorating of the optical proprieties of the violet InGaN LD. The polarization in the active region of the InGaN LD has been estimated by the blue shift of the wavelength and it is found that the blue shift of the wavelength depends on the QW thickness. The major simulation result has shown that the best properties of violet InGaN LD can be obtained with smaller QW thickness, where more carriers can be restricted, stayed and overlapped inside the QW which leads to a larger stimulated recombination rate and optical material gain which in turn increase the output power of the LD; while decreasing the threshold current of the LD.     

Estimation of the optical properties of seawater from measurements of exit radiance

An inverse analysis for simultaneous estimation of the radiation phase function, single scattering albedo and optical thickness in natural waters, from the knowledge of the exit radiance measurements, is presented. A forward and an inverse model are utilized in our analysis. The forward model uses an analytical discrete-ordinates method for solving the radiative transfer equation and the inverse model contains an algorithm for least-squares estimation that is iteratively solved for retrieving the desired optical properties. The experimental data are simulated with synthetic data corrupted with noise. The results show that the optical properties, with the exception of the optical thickness, can be recovered with high accuracy, even for data with up to 10% noise.