Ge团簇组装纳米薄膜的制备及光学性质

用惰性气体凝聚淀积技术制备半导体Ge团簇及其构成纳米薄膜。利用透射电子显微镜(TEM)、原子力显微镜(AFM)及光谱分析方法对所获得的样品进行分析研究。分别在室温和液N2冷却条件下获得了具有2种不同微结构和形貌特征的氧化层包裹的Ge团簇组装薄膜。紫外一可见光光谱分析表明,这类纳米结构薄膜具有1．0～2．9eV的光学带隙蓝移,并可用量子限制效应来解释其起源。     

非晶硒化镉微区结构及光吸收性能

报道了通过实验研究淀积条件对非晶硒化镉（α－ＣｄＳｅ）薄膜的微区结构及光吸收性能的影响。在此基础上寻求该样品微区结构对光吸收性能产生影响的规律性。     

C/FePt/Fe纳米薄膜的微结构和磁特性

利用超高真空磁控溅射方法制备了一系列不同C层厚度的C/FePt/Fe纳米薄膜,然后进行原位高温退火。应用X射线衍射仪(XRD)分析了样品的晶体结构,利用扫描探针显微镜(SPM)观测了表面形貌和磁畴结构,通过振动样品磁强计(VSM)测量了磁性。结果表明,薄膜的微结构和磁特性随C覆盖层厚度的变化有着非常显著的变化。C的加入使样品表面更加光滑,使10 nm厚的C覆盖层样品获得了0.3 nm的粗糙度和3.8 nm的颗粒尺寸。C覆盖层减弱了磁性颗粒间的磁偶极作用,同时减弱了磁性颗粒间的交换耦合作用,提高了L10织构的有序化程度,进而增大了样品的矫顽力,矫顽力达到了987 kA/m。     

PbSe量子点的制备与近红外波段光学性质研究

通过化学溶液体系中反应温度与原料配比的控制获得了尺寸分布均匀的窄带隙半导体PbSe量子点。利用吸收光谱、X射线衍射（XRD）、透射电子显微镜（TEM）和高分辨透射电子显微镜（HRTEM）等手段研究了化学溶液法制备的PbSe量子点形貌、尺寸分布及红外吸收等特性。结果表明,所获得的量子点尺寸分布均匀,结晶性良好,并实现了第一吸收峰在885 nm～2 200 nm范围内可调的PbSe量子点。     

一种红外硒化物玻璃的光学常数及其增透膜

通过对不同厚度样品的红外透射比测量，经反演迭代计算得到了一种中红外硒化物玻璃的光学常数，并进行了误差模拟分析。设计出了的规整的增透膜系并给出实际的制备结果。最后给出了非规整膜系的设计结果和光学性能。     

Selenide Glass Optical Fiber Doped with Pr3+ for U‐Band Optical Amplifier

Pr³⁺‐doped selenide glass optical fiber, which guarantees single‐mode propagation of above at least 1310 nm, has been successfully fabricated using a Ge‐Ga‐Sb‐Se glass system. Thermal properties such as glass transition temperature and viscosity of the glasses have been analyzed to find optimum conditions for fiber drawing. Attenuation loss incorporating the effects of an electronic band gap transition, Rayleigh scattering, and multiphonon absorption has also been theoretically estimated for the Ge‐Ga‐Sb‐Se fiber. A conventional double crucible technique has been applied to fabricate the selenide fiber. The background loss of the fiber was estimated to be approximately 0.64 dB/m at 1650 nm, which can be considered fairly good. When excited at approximately 1470 nm, Pr³⁺‐doped selenide fiber resulted in amplified spontaneous emission and saturation behavior with increasing pump power in a U‐band wavelength range of 1625 to 1675 nm.     

Conversion of Direct to Indirect Bandgap and Optical Response of B Substituted InN for Novel Optical Devices Applications

Optical properties of B$_{rm x}$In$_{1 - {rm x}}$N are calculated as a function of the varying concentration of Boron and Indium. Indium is gradually replaced by Boron and optical properties of the resulting materials are studied. The fractional concentration of Boron is increased gradually from ${rm x} = 0$ to ${rm x} = 1$ in steps of 0.25. The bandgap increases with the increasing Boron concentration, from 0.95 eV for pure InN to 5.6 eV for BN. A unique behavior of BN in zinc-blend phase is observed, that is, it shifts from indirect to direct bandgap semiconductor by the substitution of In on B sites. This behavior can be used to make novel and advanced optical devices. Frequency dependent reflectivity, absorption coefficient, and optical conductivity of B$_{rm x}$In$_{1 - {rm x}}$N are calculated and found to be the constituent's concentration dependent. The region of reflectivity, absorption coefficient and optical conductivity shifts from lower frequency into the higher frequency as the material goes from pure InN to pure BN.      

超短激光脉冲在共振光子带隙结构中的存储

采用时域有限差分方法求出了麦克斯韦-布洛赫方程的孤子解,数值模拟了由共振吸收原子按布拉格结构所排列而形成的″主动光子晶体″中产生″慢光子″和″静止光子″的方法.结果证明,如果使入射脉冲面积等于一个合适的值,无须对介质作任何初始激发,具有一定包络形状的脉冲可以在共振光子带隙结构中演化为空间局域化的振荡间隙孤子或静止间隙孤子.此外,理论上也模拟了间隙孤子分裂的情况.我们研究的结果证明,多个间隙孤子可以连续地自发局域化于同一结构中,因此,有效的光能就能以原子相干态的形式在共振光子带隙结构中存储,响应时间为亚皮秒的光子操控将有可能实现.     

Microstructure Fiber Based Optical Parametric Oscillators

The current status of fiber based optical parametric oscillators is presented with a focus on pulsed systems employing microstructure fibers. It is shown based on standard expressions for parametric processes in optical fibers that systems employing short (less than a few cm) optical fibers lead to superior performance in terms of wavelength tunability and output power. Practical guidelines for realizing a working system are given. These devices are now practical as ultrafast pulsed-light sources and for extending the wavelengths of operation of existing mode-locked fiber lasers.      

溶胶-凝胶法制备掺镉ZnO薄膜及光学禁带研究

主要研究掺镉ZnO薄膜的光学禁带。采用溶胶-凝胶(Sol-Gel)旋转涂覆法,在Si(100)上生长掺镉ZnO薄膜,对薄膜的XRD分析表明,掺镉ZnO薄膜仍为六角纤锌矿结构,并沿c轴择优取向生长。通过实验优化出本工艺条件下的较佳参数:退火温度为800℃,x(Cd)=6%~8%;以普通玻璃为基片的透射光谱表明掺镉ZnO薄膜的禁带宽度约为3.22 eV,比纯ZnO晶体禁带宽度3.30 eV明显减小,适度掺镉可降低薄膜的光学禁带宽度。     

黑硅微结构与光学特性研究

利用无掩模反应离子刻蚀法制备黑硅,研究了黑硅微结构密度和高度对其光学特性的影响.采用场发射扫描电子显微镜和带积分球的紫外-可见-近红外分光光度计分别表征黑硅微结构形貌和光学特性.研究结果表明,黑硅微结构密度增大和高度增加,则黑硅吸收率增大,高度较大的微结构更加有利于增强黑硅近红外光吸收.无掩模反应离子刻蚀法制备的黑硅的吸收率在高温退火过程中保持稳定.     

Direct Observation of Bandgap Oscillations Induced by Optical Phonons in Hybrid Lead Iodide Perovskites

Hybrid organic–inorganic perovskites such as methylammonium lead iodide have emerged as promising semiconductors for energy‐relevant applications. The interactions between charge carriers and lattice vibrations, giving rise to polarons, have been invoked to explain some of their extraordinary optoelectronic properties. Here, time‐resolved optical spectroscopy is performed, with off‐resonant pumping and electronic probing, to examine several representative lead iodide perovskites. The temporal oscillations of electronic bandgaps induced by coherent lattice vibrations are reported, which is attributed to antiphase octahedral rotations that dominate in the examined 3D and 2D hybrid perovskites. The off‐resonant pumping scheme permits a simplified observation of changes in the bandgap owing to the A_g vibrational mode, which is qualitatively different from vibrational modes of other symmetries and without increased complexity of photogenerated electronic charges. The work demonstrates a strong correlation between the lead–iodide octahedral framework and electronic transitions, and provides further insights into the manipulation of coherent optical phonons and related properties in hybrid perovskites on ultrafast timescales.     

脉冲激光改性金属纳米薄膜的等离子体特性

在室温环境下,实验采用Nd\:YAG光纤脉冲激光器辐照银(Ag)、铜(Cu)、铝(Al)三种光滑连续的金属薄膜,制备出了对应的三种金属纳米颗粒薄膜。通过调节激光扫描速率可以实现三种金属纳米颗粒薄膜的局域表面等离子体共振(LSPR)波长和强度的调谐。其中,Ag纳米颗粒薄膜在可见光波段的等离子体吸收峰的波长和强度均表现出较宽的调谐范围,Cu纳米颗粒薄膜在可见光波段的等离子体吸收峰的波长和强度均表现较小的调谐范围,Al纳米颗粒薄膜在紫外光波段的等离子体吸收峰窄而尖锐,且LSPR波长调谐范围也较小。与激光辐照前的三种金属薄膜相比,激光辐照后生成的三种金属纳米颗粒薄膜出现了更强的表面增强拉曼散射信号。有限差分时域仿真模拟出的样品的电场强度分布与实验得到的表面增强拉曼散射结果一致。     

Microstructure and Thermoelectric Properties of Screen-Printed Thick Films of Misfit-Layered Cobalt Oxides with Ag Addition

Thermoelectric properties of thick (~60???m) films prepared by a screen-printing technique using p-type misfit-layered cobalt oxide Ca₃Co₄O_9+?? with Ag addition have been studied. The screen-printed films were sintered in air at various temperatures ranging from 973?K to 1223?K. After each sintering process, crystal and microstructure analyses were carried out to determine the optimal sintering condition. The results show that the thermoelectric properties of pure Ca₃Co₄O_9+?? thick film are comparable to those of cold isostatic pressing (CIP) samples. We found that the maximum power factor was improved by about 67% (to 0.3?mW/m?K²) for film with proper silver (Ag) metallic inclusions as compared with 0.18?mW/m?K² for pure Ca₃Co₄O_9+?? film under the same sintering condition of 1223?K for 2?h in air.     

On the Phase Composition,Morphology, and Optical and Electronic Characteristics of AlN Nanofilms Grown on Misoriented GaAs(100) Substrates

Semiconductors - Thin AlN nanofilms are produced by reactive ion-plasma deposition onto GaAs(100) substrates misoriented with respect to the 〈100〉 direction to different degrees. It...     

射频磁控溅射ZnO薄膜的微结构与光学特性

研究了膜厚对ZnO薄膜微结构和光学性能的影响。采用射频磁控溅射法在单晶硅(111)和玻璃基片上制备了不同厚度的ZnO薄膜。通过X射线衍射、原子力显微镜和紫外可见光谱对薄膜进行了表征。结果表明薄膜结晶性能良好,在(002)晶面具有明显的c轴取向。随着薄膜厚度的增加,透射率下降,吸收边红移,禁带宽度逐渐减小。     

CdS纳米薄膜的水浴法制备与表征

CdS是一种直接能隙半导体，其带隙约为2．42eV，是一种良好的太阳能电池窗口层材料和过渡层材料。化学水浴法沉积CdS薄膜具有工艺简单，成本低廉，成膜均匀、致密以及可大面积生产等优点。本文通过对化学水浴法沉积CdS薄膜的研究，阐述了CdS膜的生成和生长过程及其机理，并不断优化此方法中的各种工艺参数，得到了适合做铜铟镓硒薄膜太阳能电池过渡层的CdS薄膜，并对该薄膜的形貌、结构和性能进行了分析。     

微结构光纤光栅谐振峰的分析

利用光束传播法对微结构光纤布拉格光栅谐振特性进行了模拟研究.验证了微结构光纤光栅的多谐振峰结构,并且谐振峰数量取决于内包层直径;定量地研究了微结构光纤光栅掺锗纤芯尺寸对整体反射率、各谐振峰强度和谐振波长漂移的影响,从而为设计光敏微结构光纤提供参考依据;提出当这种光栅产生合适的线性啁啾时,可获得宽带可调谐光谱,三角形微结构光纤光栅啁啾系数等于0.0012时可产生接近15nm的3dB宽带光谱.