脉冲激光退火纳米碳化硅的光致发光

采用XeCl准分子脉冲激光退火技术制备了纳米晶态碳化硅薄膜(nc-SiC),并对薄膜的光致发光(PL)特性进行了分析。结果表明,纳米SiC薄膜的光致发光表现为300～600 nm范围内的较宽发光谱带,随退火激光能量密度的增加,nc-SiC薄膜398 nm附近的发光峰相对强度增加,而470 nm附近发光峰相对减小。根据nc-SiC薄膜的结构特性变化, 认为这两个发光峰分别来源于6H-SiC导带到价带间的复合发光和缺陷态发光,并且这两种发光过程存在竞争。     

AuSi_x(x=1/2,1/7)纳米颗粒的制备及光致发光性能研究

采用射频磁控溅射法在n型单晶Si(100)衬底上制备Au/Si/Au多层薄膜,并在300℃真空原位退火30min。扫描电子显微镜(SEM)及透射电子显微镜(TEM)观察发现,退火前样品表面是一层平整的薄膜,而退火后样品表面形成均匀分布的岛状纳米颗粒,颗粒直径为10～20nm,面密度约1×1011cm-2。X射线光电子能谱(XPS)及TEM分析表明,退火后样品表面形成单晶结构的AuSix(x=1/2,1/7)纳米颗粒。室温下对退火后样品的光致发光(PL)特性进行测试,样品在580,628和700nm处出现三个发光峰,经过分析这些发光峰与样品表面的SiO2结构,AuSix纳米颗粒周围的悬挂键等缺陷以及样品表面SiO2纳米结构中的无桥联氧等因素有关。     

氢等离子体气氛中退火多孔硅的表面和光荧光特性

用电化学腐蚀法制备了多孔硅(PS),在氢等离子体气氛中不同温度下对多孔硅样品进行了退火处理,并进行了光致发光(PL)谱和原子力显微镜(AFM)表面形貌的测量。不同退火温度给PS表面形态带来较大变化,也影响了其PL谱特性。在退火的样品中观察到的PL谱高效蓝光和紫光谱带,我们认为主要源于量子限制发光峰和非平衡载流子被带隙中浅杂质能级所俘获而引起的辐射复合所产生的。在420—450℃退火处理的多孔硅的PL谱上观察到了一个未见诸于报道的紫光新谱带(3．24eV,382nm),其发光机理有待于进一步研究。     

玻璃中CdSeS纳米晶体的室温光致发光谱

对掺有过饱和的镉、硒和少量硫的玻璃在500～800℃分别退火4h,生长了不同尺寸的CdSe_1-xS_x纳米晶体。测量了纳米晶体的室温吸收光谱和光致发光(PL)光谱,550℃生长的样品在300～800nm的范围没有观察到吸收和发光峰,表明温度低于550℃玻璃中不能形成纳米晶体。生长温度在600～650℃,纳米晶体的PL光谱主要为两个宽的发光带,即带边激子发光带和通过表面态复合的发光带。随着生长温度的升高,带边复合发光的蓝移减小,通过表面态的发光逐渐消失,并出现了叠加于宽发光带上的一系列明显的弱发射峰。不同温度生长的样品中,叠加峰的能量相同。同一样品中叠加峰的能量不随激发光波长的变化而变化。     

有序ZnO纳米阵列的制备及其光学特性

纳米球刻蚀技术和磁控溅射方法在普通玻璃衬底上制备有序氧化锌(ZnO)纳米阵列。利用扫描电子显微镜对样品表面形貌进行了观测,并对样品进行荧光(PL)光谱测试。结果表明,相比于普通ZnO薄膜,ZnO纳米阵列的有序结构可以提高在紫外区域的发光性能,减少蓝绿光的发射缺陷。研究了不同ZnO纳米阵列粒径大小和不同ZnO纳米阵列的厚度对其光学性质的影响。溅射时间30min的有序ZnO纳米阵列样品的质量和结晶状态较好,随着聚苯乙烯(PS)纳米球粒径的减小,样品吸收峰和荧光光谱均发生"蓝移"。     

稀土Nd,Ce掺杂硅基薄膜光致发光特性

测量了Nd,Ce稀土离了注入Si基晶片，在不同离子注入剂量、不同退火条件下的室温光致发光（PL）谱，结果表明它们均具有蓝、紫发光峰，且发光稳定。在一定范围内发光效率随掺杂浓度的增加而增大，随退火条件的不同而改变。运用原子力显微镜（AFM）对样品的表面形貌进行了观察，结果显示，样品表面颗粒大小、粗糙度将影响其发光效率。表面颗粒大小均匀，均方根粗糙度小的样品发光效率较高。通过对样品的卢瑟福背散射（RBS）能谱测量，对样品的表面结构进行了探讨，并讨论了表面结构与光致发光特性之间的联系。对样品的发光机理作了初步探讨。     

绝缘氧化层上自离子注入Si薄膜W线发光性能的调控

对SOI基片上的Si薄膜进行了一系列Si⁺自注入和热退火的改性实验,并利用低温光致发光(PL)光谱对这些Si薄膜样品的发光性能进行了测试. 在这些SOI样品的PL光谱中观察到了丰富的光学结构,包括D₁,D₂,D₃,X以及异常尖锐的W线. 通过对比在同等光谱测试条件下的W线归一化强度,获得了针对SOI基片发射W线较为理想的自注入和热退火参数. 同时,还对D系列发光峰以及W线的缺陷起源和光学性质进行了很好的讨论. 关键词： SOI结构 自离子注入 W线 近红外发光器件     

包埋于氮化硅薄膜中的硅团簇的光致发光特性

采用等离子体增强化学气相沉积(PECVD)技术,在低温下制备了富硅氢化氮化硅薄膜。利用红外吸收(IR)谱,光电子能谱(XPS)和光致发光(PL)谱,研究了在不同温度下退火的薄膜样品的结构和发光特性。在经过低温退火的薄膜中观测到一个强的可见发光峰。当退火温度较高时,随着与硅悬键有关的发光峰消失,可见发光峰位发生了蓝移。讨论了退火对薄膜中硅团簇的形成及其对发光的影响。根据Raman谱,计算了氮化硅薄膜中硅团簇的尺寸大小。通过实验结果和分析,我们认为PL谱中较强的室温可见发光峰来自于包埋于氮化硅中的硅团簇。     

ZnO∶V薄膜后退火处理前后的微结构与发光特性

利用溶胶-凝胶(Sol-gel)法在单晶硅(100)衬底上分别制备了ZnO∶V薄膜和纯ZnO薄膜。为进一步研究后退火对ZnO∶V薄膜结构和发光性质的影响,在两段式快速退火后又在800℃下进行了后退火处理。X射线衍射的结果表明:后退火处理前,钒(V)的掺入使ZnO结晶质量变差,而800℃退火处理后,从ZnO的衍射峰中可以看出,相对于无V杂样品其结晶质量变好。扫描电子显微镜形貌图中可以看出制备的样品薄膜颗粒大小均匀,薄膜致密度较高。光致发光(PL)谱的研究表明:ZnO∶V薄膜在800℃退火处理后,紫外和绿带发光峰均增强,但紫外发光峰增强得更多;与同样条件下制备的纯ZnO薄膜的PL谱比较,发现V掺杂后样品的紫外激子复合发光峰的强度明显增强且峰位发生蓝移,而缺陷引起的绿带发光峰的强度降低。     

ZnO：V薄膜后退火处理前后的微结构与发光特性

利用溶胶-凝胶(Sol-gel)法在单晶硅(100)衬底上分别制备了ZnO:V薄膜和纯ZnO薄膜。为进一步研究后退火对ZnO:V薄膜结构和发光性质的影响,在两段式快速退火后又在800℃下进行了后退火处理。X射线衍射的结果表明:后退火处理前,钒(V)的掺入使ZnO结晶质量变差,而800℃退火处理后,从ZnO的衍射峰中可以看出,相对于无V杂样品其结晶质量变好。扫描电子显微镜形貌图中可以看出制备的样品薄膜颗粒大小均匀,薄膜致密度较高。光致发光(PL)谱的研究表明:ZnO:V薄膜在800℃退火处理后,紫外和绿带发光峰均增强,但紫外发光峰增强得更多;与同样条件下制备的纯ZnO薄膜的PL谱比较,发现V掺杂后样品的紫外激子复合发光峰的强度明显增强且峰位发生蓝移,而缺陷引起的绿带发光峰的强度降低。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.