共查询到19条相似文献,搜索用时 78 毫秒
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研究了多种Rh:BaTiO3和Ce:BaTiO3晶体样品的受激背向光折变散射自抽运相位共轭特性和响应时间特性.结果表明,入射光与晶体a面或b面法线的夹角较大时,自抽运相位共轭光有更高的反射率、更快响应时间.利用前向二波耦合特性和相向二波耦合特性对实验现象给予合理的解释.实验结果表明,多数Ce:BaTiO3晶体比Rh:BaTiO3晶体的共轭光反射率高.
关键词:
钛酸钡晶体
二波耦合
自抽运相位共轭
响应时间 相似文献
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研究了纯及掺杂LiNbO3(下简写为LN)晶体z向通光的锥光干涉图。纯LN,在45℃和75℃附近,双折射率均有异常变化,晶体由单轴变为双轴晶。掺杂(Fe,Cr,Cu)LN也有类似的变化,但变化的温度范围被加宽。分别测量了折射率n0和ne,在这两个温度附近有异常跳变。通过与x方向加电场的室温锥光图相比较,可以认为在75℃附近的双折射异常变化是相当于离子位移在x方向产生105V/m量级的内电场所引起的。
关键词: 相似文献
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Laevorotatory crystals of isomorphous Bi12SiO20 and Bi12GeO20 are shown, by use of the anomalous X-ray scattering component in the structure amplitudes, to have identical chirality (handedness of atomic arrangement) in contrast with the case of NaC103 and NaBrO3, in which crystals of the same chirality rotate plane polarized light in opposite senses. 相似文献
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S. A. Sveleba I. V. Karpa I. M. Katerynchuk O. V. Semotyuk R. M. Shymkiv I. M. Kunyo O. I. Fitsych 《Journal of Applied Spectroscopy》2011,78(2):228-233
This a study of the optical transmission of [N(CH3)4]2ZnCl4 and [N(CH3)4]2CuCl4 crystals in the incommensurate phase when a defect density wave is present. It is found that an anomalous reduction in the
transmission coefficient is caused by scattering of light owing to a realignment of the superstructure during transitions
between metastable states. When a defect density wave is present, the anomalous optical transmission of the crystal is related
to the scattering of light on superstructure inhomogeneities produced by a superposition of existing modulation waves. 相似文献
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S.I. Marennikov V.A. Orlov Yu.N. Fomin B.I. Kidyarov 《Solid State Communications》1978,26(10):649-652
The experimental investigation of the temperature dependence of spectra of spontaneous Raman light scattering on polaritons in α-LiJO3 crystal has been carried out. An anomalous broadening of the frequency-angular spectrum of scattered radiation was found in the region of phase transition α→γ→β at 256°C. It is assumed that this phenomenon is due to an anomalous increase of non-linearity of the third order and, hence, of the probability of the four-particle scattering process at which a pumping photon is decayed into a photon and two polaritons during a common act. 相似文献
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V. N. Molchanov B. A. Maksimov A. F. Kondakov T. S. Chernaya Yu. V. Pisarevskii V. I. Simonov 《JETP Letters》2001,74(4):222-225
Precision X-ray structural studies of the La3Nb0.5Ga5.5O14 and Sr3Ga2Ge4O14 single crystals were carried out. The space group P321 was confirmed. The anomalous X-ray scattering was taken into account to establish the absolute structures (chirality) of the crystals; they proved to be of different sign. The structural features responsible for the optical activity of crystals were revealed, and the dependence of the magnitude and sign of specific rotation on the structural parameters of these compounds were determined. 相似文献
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The specific features of diffuse X-ray scattering in BaTiO3, KNbO3, and PbTiP3 perovskite crystals have been investigated. The former two perovskite compounds in cubic, tetragonal, and orthorhombic phases exhibit anomalous sheets due to diffuse X-ray scattering, whereas no similar sheets are observed in the case of diffuse X-ray scattering in PbTiO3. For these compounds, the phonon spectra are calculated in the quasi-harmonic approximation within the polarizable-shell model, and the mechanism of stabilization of the soft mode above the temperature of the phase transition to the ferroelectric state is considered. It is demonstrated that, in the cubic phase of BaTiO3 and KNbO3 crystals, there exist quasi-one-dimensional “soft” modes of vibrations of ions in M-O-M-O- chains, where M = Ti or Nb. In PbTiO3, this feature of the soft mode has not been revealed. The pair correlation functions of simultaneous atomic displacements in BaTiO3, KNbO3, and PbTiO3 are determined and used to calculate the intensity of diffuse X-ray scattering. The results obtained are in good agreement with experimental data. This is a strong argument in support of the hypothesis that the specific features of diffuse scattering are associated with the existence of quasi-one-dimensional correlations of atomic displacements in the soft optical mode and that the ferroelectric transition in perovskites is a displacive ferroelectric phase transition. The possible influence of the specific features revealed in the phonon spectra of the perovskite crystals on the processes of nuclear magnetic resonance and X-ray absorption (extended X-ray absorption fine structure spectra) is briefly discussed. 相似文献