纳米尺寸的ZnO晶体高压相变的拉曼散射研究(英文)

Weperformedthehigh-pressureRaman measurementofthethreenanosizedZnOcrystals. Wefoundthesmallerthesize,thehigherthe pressuretoinducethephasetransitionfrom w櫣rzitetorock-saltstructure. High-pressureRamanmeasurementsof nona-shapedZnOcrystalswerepreformed.The…     

富勒稀纳米颗粒的拉曼光散射(英文)

pacc:7560J,7830WepresentresultsofRamanscatteringspec trainvestigationsinfluoroorganicnanoparticles:longzigzagmoleculesCnF2n 2withdifferentn valueandultradispersivefluoroorganicpowder.Ramanspectrahavebeenrecordedforlow-frequencyregion(0-200cm-1),whereres o…     

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, 623.50 nm),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。     

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。     

拉曼对光散射的实验研究

介绍了拉曼的生平和对物理学的主要贡献，回顾了他从观察海水的蓝色人手，继而发现气体、液体对光的散射规律，一直到发现物质的散射光不仅包含原来的波长，而且还包括与原入射光不同的其他波长的散射的研究过程，并讨论了他的成功对我们的启示．     

DKDP晶体的拉曼散射谱分析

根据空间群理论分析和指认了磷酸二氘钾晶体[K(D_xH_1-x)₂PO₄,简称DKDP]的拉曼活性晶格振动模,测量了其室温拉曼光谱。结果表明DKDP晶体的晶格振动谱主要是由D₂PO-₄阴离子团簇的内振动引起的。与H₂PO-₄阴离子稀溶液的拉曼谱和NaD₂(PO₄)₂晶体的拉曼谱比较,DKDP晶体中D₂PO-₄阴离子的四个特征内振动模可被指认为881 cm-1(ν₁),357 cm-1(ν₂),514/541 cm-1(ν₃),965 cm-1(ν₄)。     

微波布拉格衍射中立方晶体晶面衍射测量与模型选取讨论

在微波布拉格衍射实验中,通过对立方晶体模型晶格常数参量选取,测定(110)面入射角与衍射强度变化关系,来验证衍射极大值在随入射角变化而变化的过程是否满足布拉格定律.同时可在一定入射角变化范围内,限定衍射级数的大小,讨论只改变接收端角度时,(100)面与(110)面衍射极大值时晶格常数所在范围,并从理论上给出同时测定两晶面可限定的衍射级数与晶格常量的范围.     

KDP晶体拉曼散射角度特性

利用群理论详细分析了磷酸二氢钾(KDP)晶体的拉曼振动模式,得出了其拉曼振动模的归类。并采用拉曼光谱仪测量了Z切退火KDP晶体X(ZZ)珡X,Z(XY)珚Z和Y(XY)X三种散射配置和未退火KDP晶体Z(XY)珚Z配置下的拉曼光谱。根据拉曼选择定则得出X(ZZ)珡X,Z(XY)珚Z和Y(XY)X散射配置下的拉曼峰分别对应A1,B2(LO),B2(TO)对称类振动模,但在Z(XY)珚Z配置下的拉曼光谱中除了B2模,还观察到了A1模,而在Y(XY)X配置下的拉曼光谱中只有B2模,且退火和未退火晶体Z(XY)珚Z配置下的拉曼光谱无明显差别,此结果表明KDP晶体的对称性降低,在背向散射时A1模也具有角度特性,但与晶体的内应力无关,这是由KDP晶体内部结构决定的。     

Raman Scattering in Three-Dimensional Photonic Crystals

The optical properties of three-dimensional photonic crystals associated with the form of reflection spectra from their surface (appearance of a forbidden gap in the energy spectrum) and with the specific features of Raman scattering are analyzed. Idealized models of the energy band structure of photonic crystals are studied. Expressions for the group velocity of photons with energy close to the forbidden gap are derived. Experimental results on the Raman scattering in photonic crystals based on artificial opal as well as in fused silica are discussed. Bands due to quantum-size effects (presence of nanoclusters in fused silica and nanoglobules forming the lattice of globular photonic crystals) were manifested in the spectra of inelastic light scattering. It is proposed to use photonic crystals for the creation of sensitive sensors of organic and inorganic substances using modern Raman techniques.     

Raman and Hyper-Rayleigh Scattering in Lithium Tetraborate Crystals

Experimental studies of Raman scattering and the infrared reflection spectra of lithium tetraborate crystals were carried out within a broad temperature range with various polarization geometries. The crystals studied are characterized by record values of radiation resistance, transparence within a broad spectral range including the ultraviolet region, and nonlinear optical properties. A group-theoretical analysis of the vibrational spectra of this crystal was performed and fundamental vibrational terms were assigned to the symmetry types of the point group as well as the polarizations of the corresponding modes. The effective Raman cross section was measured and was found to be one order of magnitude higher than those of the known crystals, in which the stimulated Raman scattering (SRS) was observed. The nonlinear optical and electrooptical coefficients were evaluated and were found to be consistent with the results of independent measurements. The effect of a drastic increase in the intensity of quasi-elastic light scattering at 253 K was registered. It was associated with the phase transition that consists of the disordering of lithium ions with respect to the rigid skeleton. The formation energy for Frenkel defects in the lithium sublattice and the activation energy of the ionic conduction when heating the sample were calculated from the obtained temperature dependences of the intensity of quasielastic and hyper-Rayleigh light scattering.     

Overtone Raman Scattering in Lithium Tantalate Single Crystals

Optics and Spectroscopy - Overtone bands in the spectral range of 1300−1920 cm–1 have been found in Raman scattering spectrum of lithium tantalate single crystals. The Raman spectra...     

晶体压致非晶化的拉曼散射研究

本文主要介绍压致非晶化研究的进展，其中包括我们对β—ＢａＢ＿２Ｏ＿４，ＬｉＢ＿３Ｏ＿５，Ｐｂ＿５Ｇｅ＿３Ｏ＿１１和Ｌｉ＿２Ｇｅ＿７Ｏ＿（１５）的拉曼散射研究结果。综述了压致非晶的结构特征，压致非晶转变机制和重新晶化过程。     

Antiresonance of Raman Scattering in CdSxSe1-x Mixed Crystals

Abstract

Resonant enhancement of the Raman scattering cross section in II - IV semiconductors has recently received much attention both theoretically and experimentally. All existing theories anticipate a monotonic increase in the scattering intensities when the scattering radiation energy approaches the direct-energy gap. Contrary to them in an early Raman study of CdS¹ a cancellation of scattering efficiencies for the two TO modes prior to the onset of the resonance was pointed out. In a latter work on pure CdS Damen et al.² found even a more pronounced “antiresonance” behavior of the nonpolar E₂ phonon at 41 cm^?1. Thus, this striking feature seems to be rather common for the Raman active modes in CdS for which no electrooptic contribution to the scattering amplitude exists. The experimental data were qualitatively explained by assuming a destructive addition between nonresonant and the weaker resonant terms in LoudoN′s expression for the first-order Raman tensor³. Consequently the cancellation energy difference /E_G - hw_L/ depends on the ratio of the resonant term to the nonresonant terms.     

Inverse Raman Scattering by Polaritons in LiNbO3 Single Crystals

Experimental studies of IRS by polaritons in LiNbO₃ are reported for the first time. In compliance with the classification of IRS-scattering geometries by polaritons in uniaxial crystals [3] for different polarisation directions of laser and anti-Stokes continuum two A₁-type polaritons and also E-type-polaritons of the upper and the lower ordinary dispersion branches, respectively, could coherently be generated. Introducing a new polariton specific excitation state instead of the mechanic vibration the shortened IRS equations without small signal approximation are solved in the stationary case and for “responseless” polariton fields. The increase of the laser field and the decrease of the anti-Stokes field show for α_px ? 1 the same behaviour as Stokes growth and laser depletion, respectively, in the case of SRS by dipole inactive levels. Model calculations show the necessity of the used intra cavity arrangement for photographic registration of IRS-polariton spectra.     

硼酸锂系列晶体的高压拉曼散射研究

本文进行了硼酸锂系列晶体的高压拉曼散射及其压致相变的研究。对于三硼酸锂（ＬｉＢ３Ｏ５），我们发现在５．０ＧＰａ有一可逆的晶态到晶态的相变，在２７．０ＧＰａ有一不可逆的晶态到非晶态的相变。二硼酸锂（Ｌｉ２Ｂ４Ｏ７）不可逆压致非晶相变发生在３２．０ＧＰａ附近。对于一硼酸锂，我们研究了０—５５．８ＧＰａ范围内的高压拉曼光谱，只在２．０ＧＰａ发现了一个晶态到晶态的相变，但未发现不可逆压致非晶化现象。在硼酸锂系列晶体中，不可逆压致非晶化的压力随Ｌｉ２Ｏ的含量的增加而升高。硼酸锂晶体中Ｌｉ２Ｏ的含量越高，压致非晶化越不容易发生，这与熔体急冷法制备硼酸锂玻璃的规律是一致的。     

The Bragg Diffraction of Light at Acoustophotorefractive Holographic Gratings in Gyrotropic Cubic Crystals

We investigate diffraction of light at phase holographic-type gratings recorded by a piezoactive ultrasonic wave in gyrotropic cubic photorefractive crystals. We show that the efficiency of diffraction at a holographic grating can be increased substantially by applying a d.c. field to a crystal under the conditions of a longitudinal electrooptical effect; elliptical polarization of diffracted light is determined by electrically induced anisotropy of a crystal in the piezofield of a photorefractive grating, by the external electric field, detuning of phase synchronism, gyrotropy of the crystal, ultrasound frequency, and the time of recombination of charge carriers.