KDP晶体受激拉曼散射特性

详细比较了磷酸二氢钾(KDP)晶体的自发拉曼散射和受激拉曼散射光谱,在受激拉曼散射(SRS)中观察到了自发拉曼散射中最强的振动模的三阶Stokes光(559.43,589.74,623.50nm),由于其他振动模的受激拉曼散射增益系数较小,其SRS光谱未观察到。另外,比较了传统生长的未退火和退火后的KDP晶体及快速生长的锥区和柱区KDP晶体的受激拉曼散射增益系数,结果表明生长方法和热退火对KDP晶体的受激拉曼散射增益系数无明显影响。     

偏振拉曼散射研究ZnO单晶纳米压痕区内的晶格畸变分布

通过结合纳米压痕和偏振拉曼散射技术对压应力影响下ZnO单晶晶格出现的变化进行了研究。位错的滑移是导致ZnO单晶中出现多处塑性变形的原因而非相变。之后采用偏振拉曼Mapping成像技术以E2(high)模为对象, 监视其在整个压痕区内的强度变化分布。在压痕区中心累积的应力通过位错的滑移而释放, 同时导致压痕区中心处的晶格畸变程度最为严重。伴随着晶格失配的加剧, 拉曼选择定则放宽, 在Z(XX)配置下较弱的LO得到增强, 原本非拉曼活性的B1(high)模出现。此外, 在Z(XY)偏振下压痕区左侧的拉曼光谱中观察到位于130 cm-1处的拉曼异常振动模。此峰的出现可能与压痕区左侧由刃位错所形成的应力场吸引间隙离子导致的晶格畸变有关。     

KDP晶格振动模和生长机制的拉曼光谱研究(英文)

用空间群理论分析和指认了KDP晶体的拉曼活性晶格振动模 ,测量了晶体以及生长溶液的拉曼光谱 ,重点分析了出现在固 /液界面附近的 91 6cm- 1拉曼峰 ,该峰被指认为扭曲的P(OH) 2 集团反对称伸缩振动。依据本文的理论分析和实验测量 ,我们认为H2 PO- 4阴离子集团的二聚物可能是KDP晶体的生长基元。     

氘含量对DKDP晶体横向受激拉曼散射增益系数的影响

本文测量了不同氘含量K(H_1-xD_x)₂PO₄晶体(DKDP晶体)在Z(XX)Y散射配置下的自发拉曼散射光谱, 并详细分析了氘含量对与横向受激拉曼散射(TSRS)增益系数有关的拉曼频移、半峰宽和散射强度的影响. 然后通过与去离子水拉曼散射对比得出了不同氘含量DKDP晶体的TSRS增益系数. 结果表明随着氘含量的增加DKDP晶体的TSRS增益系数先减小至KDP晶体的40.1%, 后增大至68.9%; 本文认为掺氘后拉曼半峰宽的变化是引起TSRS增益系数随氘含量变化的主要原因.     

掺镱钒酸钇晶体的晶格振动光谱

掺镜钒酸钇晶体是一种很有应用前景的晶体材料,由于它适合于半导体激光器泵浦的全固态激光器的要求而受到人们的普遍关注。拉曼光谱是研究材料的声子能谱分布的方法。本文根据群论对称性分类,计算了掺镜钒酸钇晶体的拉曼和红外活性振动模。选择不同几何配置的拉曼光谱,获得了不同的晶格振动模并计算了不同晶格振动模的散射效率。实验证明最强的振动模来自钒氧四面体的振动。     

BaWO_4晶体的拉曼光谱分析

BaWO4晶体是一种很有应用前景的喇曼激光晶体。本文根据对称性分类,用商群理论分析了Ba-WO4晶体的喇曼光谱。一个原胞中含有两个BaWO4分子,理论上有36个振动膜,和我们用群论计算得数目一致。其中有18支拉曼活性光学膜。我们测得了10支拉曼峰,并对测得的各个配置的拉曼峰进行了指认,其中X(ZZ)X配置921cm-1处的喇曼峰强度最强,线宽较窄,对于作为喇曼激光晶体来讲是很有益的。     

飞秒脉冲激光在铁电体中的冲击受激拉曼散射

将冲击受激拉曼散射应用于某些铁电体中 ,在时间域内分析物质晶格振动。τωα <2π是应用冲击受激拉曼散射的必要条件。使用钛宝石激光再生放大系统作为激发源 ,在LiTaO3 晶体内获得了声子电磁激元振荡模。将同种方法用于KDP ,在其铁电体相位转换点以上 5 0K的温度范围内 ,仅发现了波矢 q =6848cm- 1 ,弛豫时间常数τ0 =1 33× 10 - 1 3 s的弛豫振动软模 ,显示出KDP铁电体相位转换的弛豫特性。     

高压固相复分解反应法合成GaN晶体的拉曼散射研究

高压固相复分解(HPSSM)反应法是一种新型的金属氮化物合成方法。本文对HPSSM法合成的GaN晶体进行了高压、高温和低温原位拉曼散射研究。给出了HPSSM GaN各拉曼振动模的Grüneisen参数以及一阶拉曼频移和拉曼模半峰宽随温度变化的关系。通过SCM空间相关模型对常温常压下GaN晶体拉曼光谱拟合,得到其空间关联长度;并利用三声子耦合模型拟合变温拉曼光谱。实验所获得的物理参数同MOCVD GaN的参数进行了比较。     

Nd:LuVO_4晶体的拉曼光谱研究

采用不同的几何配置测量了Nd:LuVO4晶体的室温拉曼光谱,根据群论对称性分类计算了该晶体的红外和拉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全对称类的高温拉曼光谱,讨论了拉曼频移随温度变化的关系,认为晶体的热膨胀是引起拉曼频移变化的主要原因。     

自受激拉曼晶体Nd3+:SrMoO4的光谱性质研究

通过拉曼散射光谱,吸收光谱,荧光发射寿命和808 nm LD激发下的红外荧光光谱的实验测量,系统研究了Nd3+:SrMoO4晶体的自受激拉曼光谱性质.分析指认了拉曼散射光谱中各拉曼峰所对应的晶格振动模式,得出了其SRS活性最强的声子频率约为898 cm-1,对应于(MoO24-)离子团的完全对称光学伸缩振动Ag模;通过J-O理论对晶体的吸收谱进行了全面的光谱参数计算,得出4F3/2→I11/2跃迁的积分发射截面达O.57×10-18cm2,自发辐射概率为141.06s-1;同时,实验测得该跃迁的荧光发射寿命约为O.2 ms.最后,结合808 nm LD激发下的红外波段荧光光谱,论证了SrMoO4晶体中Nd3+离子1068 nm发射通过拉曼频移获得1180 nm一级斯托克斯激光发射的可能性,为Nd3+:SrMoO4晶体的自受激拉曼激光器研究提供了理论依据.     

GaN外延层的拉曼散射研究

ＧａＮ外延层的拉曼散射研究１李国华１韩和相１汪兆平２段树琨３王晓亮（１半导体超晶格国家重点实验室２集成光电子学国家重点联合实验室３半导体材料科学实验室中国科学院半导体研究所北京１０００８３）ＲａｍａｎＳｃａｔｅｒｉｎｇｏｆＧａＮＥｐｉｌａｙｅｒ１Ｌ...     

反斯托克斯拉曼光谱在BaTiO_3铁电相变研究中的应用

从理论上讨论了一阶和二阶斯托克斯与反斯托克斯拉曼散射截面的温度依赖关系;在２９３Ｋ至４０１Ｋ的温度范围内,测量了ＢａＴｉＯ３单晶斯托克斯和反斯托克斯过程的偏振拉曼光谱;通过对ＢａＴｉＯ３单晶斯托克斯和反斯托克斯拉曼光谱的综合分析,证实在Ｘ（ＺＺ）Ｙ几何配置下测量到的位于２７５和５１４ｃｍ－１处的强峰为一阶拉曼光谱。此结果支持了ＢａＴｉＯ３铁电相变机制的有序—无序模型。     

Bismuth-content-dependent polarized Raman spectrum of InPBi alloy

We systematically investigate the optical properties of the InP_(1-x)Bi_x ternary alloys with 0≤x≤2.46%,by using high resolution polarized Raman scattering measurement.Both InP-like and InBi-like optical vibration modes(LO) are identified in all the samples,suggesting that most of the Bi-atoms are incorporated into the lattice sites to substitute Patoms.And the intensity of the InBi-like Raman mode is positively proportional to the Bi-content.Linear red-shift of the InP-like longitudinal optical vibration mode is observed to be 1.1 cm~(-1)/Bi%,while that of the InP-like optical vibration overtone(2LO) is nearly doubled.In addition,through comparing the(XX) and Z(XY) Raman spectra,longitudinaloptical-plasmon-coupled(LOPC) modes are identified in all the samples,and their intensities are found to be proportional to the electron concentrations.     

High‐pressure polarized Raman spectra of Gd2(MoO4)3: phase transitions and amorphization

Polarized Raman spectra of a single crystal of gadolinium molybdate [Gd₂(MoO₄)₃] were obtained between 1 atm and 7 GPa. Using a mixture of alcohols as the pressure‐transmitting medium, YY, ZZ, XY components of scattering matrices were measured. The ZZ spectra were also obtained in argon. Five phase transitions and amorphization were identified. The first and second transitions are reversible, while amorphization is not. In alcohol, amorphization is observed above 6.5 GPa. With argon as the pressure‐transmitting medium, amorphization is progressive and begins above 3 GPa. The spectral changes with pressure affect the high wavenumber bands attributed to symmetric and antisymmetric MoO₄ stretching modes as well as the very low wavenumber modes such as librations of the tetrahedra. This means that both short‐range and long‐range organizations of the tetrahedra are involved in these phase transitions. The amorphization mechanism and its dependence on the pressure‐transmitting medium are discussed, and the steric hindrance between polyhedra is believed to be the most relevant mechanism. The TO and LO low wavenumber modes of A₁ symmetry, observed in the Y(ZZ)Y and Z(YY)Z geometries, respectively, below 50 cm⁻¹, soften continuously through the first three phases when increasing pressure. The strong A₂ mode observed in the Z(XY)Z spectra exhibits the same anomalous behavior by decreasing from 53 to 46 cm⁻¹ at 2 GPa. The softening of these modes is related to the orientation change of tetrahedra observed by ab initio calculations when the volume of the cell is decreased. These orientation changes can explain the wavenumber decrease of the Mo O stretching modes above 2 GPa, which indicates an increase of Mo coordination. Copyright © 2010 John Wiley & Sons, Ltd.     

The pH effects on the growth rate of KDP (KH2PO4) crystal by investigating Raman active lattice modes

We report on the dependence of the pH value on the growth rates of KDP single crystals. Extensive experimental work has been carried out in order to find the optimum pH ranges for growing KDP single crystals with suitable sizes and high optical quality. Different techniques including micro‐Raman back‐scattering spectroscopy, UV/vis/IR transmission spectroscopy and X‐ray diffraction have been employed for this investigation. Deuterated substituted single crystals of KDP and DKDP also have been grown for the investigation of growth rates and Raman active mode identification purposes. The molecular vibration modes of the grown crystals, including internal modes of PO₄ tetrahedrons molecular vibrations, external modes of optical phonons and hydrogen bonding modes have been determined exactly by micro‐Raman back‐scattering spectroscopy. The best pH values of the solution for the KDP crystal growth with reasonably higher growth rates from aqueous solutions that have been supersaturated ata temperature range of 30–50 °C have been found to be in the pH range of 3.2–5.4. Copyright © 2007 John Wiley & Sons, Ltd.     

Polarized Raman scattering and lattice eigenmodes of antiferromagnetic NdFeO3

The first‐ and second‐order Raman‐active phonons in the orthorhombic Pbnm NdFeO₃ single crystals were studied by means of polarized Raman scattering and lattice dynamics computations (LDC). The zone‐center phonons of A_g symmetry were distinguished from the B_1g eigenmodes by performing polarized Raman scattering experiments using two parallel polarization configurations, X′(ZZ)X′ and Z(X′X′)Z. With the help of LDC, we were able to assign most of the observed Raman‐active modes, including phonons of B_2g and B_3g symmetry. The LDC results indicated that among the 16 force constants employed, the one corresponding to the stretching vibration between the central Fe cation and the axial oxygen atom in a FeO₆ octahedron unit had the largest value. This suggests that the B‐site Fe cation is more tightly bound to the axial O1 ion than the other two equatorial O2 ions. It was further shown that at higher wavenumbers, the displacement of oxygen atoms contributed dominantly to the zone‐center vibrations. Copyright © 2008 John Wiley & Sons, Ltd.