铯蒸汽中受激电子喇曼散射

本文报导了利用微微秒脉冲系列在铯原子蒸汽中产生受激电子喇曼散射,得到强微微秒红外脉冲的实验结果.波长为527nm的绿光经喇曼频移产生2.28μm的红外输出,最大能量达1mJ,量子转换效率为16%.实验测量了红外辐射强度及受激电子喇曼散射的阈值对蒸汽压、泵浦光强度的依赖关系,并进行了分析和讨论.     

单模石英光纤中受激喇曼散射的研究

利用连续光纤激光器为泵浦源,对单模石英光纤中的受激喇曼散射进行了实验研究.在较低功率泵浦下,观察到由自发喇曼散射向受激喇曼散射演化的过程中,光谱不断变窄;当Stokes波信号功率较强时,观察到光谱峰值相对于泵浦波的频移量从440 cm－1转化到490 cm－1.在改进耦合系统后,不仅观察到一级喇曼频移,并且观察到了高阶Stokes光.在产生多级喇曼光谱时能量移动比较复杂,每两级的喇曼频移间隔并不完全相同.     

激光、激光技术 激光工作物质

TN2442006053962Nd∶LuVO4晶体的喇曼光谱研究=Raman spectrainvesti-gation of Nd∶LuVO4crystal[刊,中]/冉栋刚(山东大学物理与微电子学院.山东,济南(250100)),夏海瑞//光散射学报.—2006,18(2).—139-146采用不同的几何配置测量了Nd∶LuVO4晶体的室温喇曼光谱,根据群论对称性分类计算了该晶体的红外和喇曼活性振动模并与实验结果做了比较,指认了测定的特征谱线。测量并分析了Nd∶LuVO4晶体A1g全对称类的高温喇曼光谱,讨论了喇曼频移随温度变化的关系,认为晶体的热膨胀是引起喇曼频移变化的主要原因。图6表3参11(杨妹清)TN244200…     

光纤喇曼增益系数的简捷测量

基于小信号开关增益原理,采用抽运光-探测波法,利用SLD(超辐射激光二极管)作为宽带小信号探测光源,快速测量出了标准单模光纤(G.652)的频移为0.5～20 THz内的喇曼增益系数,测量结果和文献中已有的值基本吻合,所测得的光纤喇曼增益系数可用于光纤喇曼放大器的理论和实验研究,该方法同样可以对其他类型光纤的喇曼增益系数进行测量.     

LDS751染料的受激喇曼散射

报道了用532nm激光抽运LDS751染料产生720—780nm可调谐染料激光输出的同时,观察到喇曼频移为102和45cm-1的反斯托克斯线,前者谱线较强,后者较弱.与这两条强线对应的斯托克斯线未能观察到.另外,还观察到喇曼频移为34cm-1的一级和二级斯托克斯线与反斯托克斯线 关键词： LDS751染料 受激喇曼散射 喇曼位移 斯托克斯线 反斯托克斯线     

一种RDS实验装置的计算机系统

<正> 一、引言喇曼差分光谱学(Raman Difference Spectroscopy 简称 RDS)是七十年代初发展起来的一门实验技术,它要求通过一定的实验手段,在一次波长扫描过程中同时记录下两个或多个样品的喇曼光谱,并将这些谱图进行差减。这种方法在测量喇曼谱线的微小频移量方面特别有效,可大大提高仪器的测量精度毫.国外对 RDS 已有较多的研究,相比之下,国内对此却研究得甚少.据     

有限元法计算GaN/AlN量子点结构中的电子结构

根据有效质量理论单带模型，采用有限元方法(FEM)计算了GaN/AlN量子点结构中的电子结构，分析了应变和极化对电子结构的影响，计算了不同尺寸的量子点的能级，分析了量子点的大小对电子能级的影响. 结果表明，形变势和压电势提升了电子能级，而且使简并能级分裂. 随着量子点尺寸的增大，量子限制能减小，而压电势能起到更显著的作用，使电子的能级降低，吸收峰发生红移. 关键词： GaN/AlN量子点结构 有效质量理论 电子能级     

准分子激光束的喇曼组束

受激喇曼散射可以将紫外准分子激光辐射频移到特定的近紫外或可见光波长,采用喇曼整形技术可以改善斯托克斯光的光束质量,本文报道喇曼组束提高喇曼整形效率的实验结果.     

自喇曼散射及二阶色散系数对三阶飞秒孤子的影响

介绍了分步傅里叶数值方法的原理和步骤。通过数值模拟，得到随着自喇曼散射系数的增大，三阶飞秒孤子分裂的两个孤峰，左峰的超前越来越小，而右峰的延迟越来越大。从频谱上看，开始蓝移随着自喇曼散射系数的增大而增大，当增大到一定程度时，两边的频谱会中移。增加二阶色散系数，三阶飞秒孤子的裂化也会得到控制，在频域内表现为频谱中移变窄。     

飞秒光孤波传输系统中自频移的抑制

研究了飞秒光泳冲在光纤中传输时自频移的抑制问题；获得了在带宽限制放大器和非线性增益共同作用下脉宽与频移不随距离变化的近似稳态解。利用线性菌定性分析，获得了该菌态解的线性菌定条件。最后数值模拟了该稳态解在光纤系统中的传输，结果表明该菌态解在光纤系统中可稳定传输，喇曼自频移效应得到了较好的抑制。     

Relaxation of mechanical stresses in an array of Ge quantum dots obtained in Si

Raman scattering on optical phonons in Si/Ge/Si structures with Ge quantum dots grown by molecular beam epitaxy at low temperatures 200–300°C has been investigated. A pseudomorphic state of an array of Ge quantum dots to a Si matrix with an ideally sharp interface has been obtained. Features associated with the inelastic relaxation of mechanical stresses have been revealed in the Raman spectrum. Two mechanisms of stress relaxation are separated. It has been shown that the spectrum of the electronic states of the array differs significantly from the set of the discrete levels of a single quantum dot, because the relaxation is inhomogeneous.     

Resonant Raman scattering in nanostructures with InGaAs/AlAs quantum dots

Raman scattering by optical phonons in In_xGa_{1 ? x} As/AlAs nanostructures with quantum dots has been studied experimentally for compositions corresponding to x = 0.3?1 under out-resonance conditions. Features due to scattering by GaAs-and InAs-like optical phonons in quantum dots have been detected, and the phonon frequencies have been determined as a function of the dot composition. With increasing excitation energy, a red shift is observed in the frequency of the GaAs-like phonon in quantum dots, which testifies to Raman scattering selective by the size of quantum dots. Under resonant conditions, multiphonon light scattering by optical and interface phonons is observed up to the third order, including overtones of the first-order phonons of InGaAs and AlAs materials and their combinations.     

Surface enhanced Raman scattering by CdS quantum dots

Surface enhanced Raman scattering is studied in nanostructures with CdS quantum dots formed using the Langmuir-Blodgett technology. Features due to quantum dot longitudinal optical phonons are observed in the Raman spectra of both free CdS quantum dots and such dots distributed in an organic matrix. The surface enhanced Raman scattering by nanostructures with CdS quantum dots covered by an Ag cluster film is observed experimentally. Applying Ag clusters onto the nanostructure surfaces results in a sharp (40-fold) increase in the intensity of Raman scattering by optical phonons in the quantum dots. It is shown that the dependence of surface enhanced Raman scattering on the excitation energy is resonant with a maximum at the energy corresponding to the maximum absorption coefficient of Ag clusters.     

Vibrational density of states of hen egg white lysozyme

The resonant Raman scattering in GeSi/Si structures with GeSi quantum dots has been analyzed. These structures were formed at various temperatures in the process of molecular-beam epitaxy. It has been shown that Raman scattering spectra recorded near resonances with the E₀ and E₁ electronic transitions exhibit the lines of Ge optical phonons whose frequencies differ significantly from the corresponding values in bulk germanium. In the structures grown at low temperatures (300–400°C), the phonon frequency decreases with increasing excitation energy. This behavior is attributed to Raman scattering, which is sensitive to the size of quantum dots, and shows that quantum dots are inhomogeneous in size. In the structures grown at a higher temperature (500°C), the opposite dependence of the frequency of Ge phonons on excitation energy is observed. This behavior is attributed to the competitive effect of internal mechanical stresses in quantum dots, the localization of optical photons, and the mixing of Ge and Si atoms in structures with a bimodal size distribution of quantum dots.     

Competition between strain and confinement effects on the crystalline quality of InAs/GaAs (001) quantum dots probed by Raman spectroscopy

Self‐organized quantum dots (SOQDs) of InAs/GaAs (001) prepared at low growth temperatures have been carried out by Raman spectroscopy. The structural study performed on these samples using atomic force microscopy showed the presence of two families of quantum dots, and these results were confirmed by analysis of Raman spectra. The low temperature growth leads to smaller dots with nonuniform sizes. The disagreement between the lattice parameters violated the selection rules, and all Raman modes could be observed. SOQDs Raman spectrum shows contribution from the GaAs substrate, the wetting layer, InAs quantum dots and InGaAs alloys at InAs/GaAs interface. A spatial correlation model including the different vibration modes was used to adjust the experimental result. A good agreement of theoretical and experimental results was obtained. Copyright © 2012 John Wiley & Sons, Ltd.     

Optical investigation of CdS quantum dots in Langmuir–Blodgett films

Structures with CdS quantum dots produced by the Langmuir–Blodgett (LB) technique were investigated by Raman, IR, and UV spectroscopies. The confinement effect of longitudinal optical (LO) phonons in CdS quantum dots was investigated by Raman spectroscopy. Surface vibrational modes of CdS quantum dots were observed in IR spectra. It was shown experimentally that the frequency of the surface vibrational modes depends on the properties of the surrounding media. An average size of CdS quantum dots of about 3–6.4 nm was obtained from the analysis of UV measurements. Received: 1 February 1999 / Accepted: 1 April 1999 / Published online: 19 May 1999     

Resonant Raman scattering of ZnS,ZnO, and ZnS/ZnO core/shell quantum dots

Resonant Raman scattering by optical phonon modes as well as their overtones was investigated in ZnS and ZnO quantum dots grown by the Langmuir–Blodgett technique. The in situ formation of ZnS/ZnO core/shell quantum dots was monitored by Raman spectroscopy during laser illumination.     

Phonons in Ge/Si superlattices with Ge quantum dots

Ge/Si superlattices containing Ge quantum dots were prepared by molecular beam epitaxy and studied by resonant Raman scattering. It is shown that these structures possess vibrational properties of both two-and zero-dimensional objects. The folded acoustic phonons observed in the low-frequency region of the spectrum (up to 15th order) are typical for planar superlattices. The acoustic phonon lines overlap with a broad emission continuum that is due to the violation of the wave-vector conservation law by the quantum dots. An analysis of the Ge and Ge-Si optical phonons indicates that the Ge quantum dots are pseudoamorphous and that mixing of the Ge and Si atoms is insignificant. The longitudinal optical phonons undergo a low-frequency shift upon increasing laser excitation energy (2.54–2.71 eV) because of the confinement effect in small-sized quantum dots, which dominate resonant Raman scattering.     

Three-dimensional photon confinement in a spherical microcavity with CdTe quantum dots: Raman spectroscopy

We have studied the Raman spectra of a system consisting of a polystyrene latex microsphere coated by CdTe colloidal quantum dots. The cavity-induced enhancement of the Raman scattering allows the observation of Raman spectra from only one CdTe monolayer. Periodic structure with very narrow peaks in the Raman spectra of a single microsphere was detected both in Stokes and anti-Stokes spectral regions, arising from the coupling between the emission from quantum dots and spherical cavity modes.     

Resonant Raman scattering by strained and relaxed germanium quantum dots

This paper reports on the results of resonant Raman scattering investigations of the fundamental vibrations in Ge/Si structures with strained and relaxed germanium quantum dots. Self-assembled strained Ge/Si quantum dots are grown by molecular-beam epitaxy on Si(001) substrates. An ultrathin SiO₂ layer is grown prior to the deposition of a germanium layer with the aim of forming relaxed germanium quantum dots. The use of resonant Raman scattering (selective with respect to quantum dot size) made it possible to assign unambiguously the line observed in the vicinity of 300 cm^?1 to optical phonons confined in relaxed germanium quantum dots. The influence of confinement effects and mechanical stresses on the vibrational spectra of the structures with germanium quantum dots is analyzed.