共查询到19条相似文献,搜索用时 140 毫秒
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紫外激光诱导近化学计量比钽酸锂晶体铁电畴反转 总被引:1,自引:0,他引:1
对紫外激光诱导近化学计量比钽酸锂晶体铁电畴反转进行了实验研究。波长为351 nm的连续紫外激光被聚焦在近化学计量比钽酸锂晶体的-z表面,同时沿与晶体自发极化相反的方向施加均匀外电场。实验证实紫外激光辐照可以有效地降低晶体畴反转所需的矫顽电场,采用数字全息干涉测量技术检测证实在激光辐照区域实现局域畴反转。研究表明采用紫外激光诱导可以实现对近化学计量比钽酸锂晶体铁电畴反转的局域控制。提出了物理机理的理论分析,认为外电场和激光辐照场的共同作用在晶体内部产生高浓度、大尺寸的缺陷结构,缺陷一定程度上降低畴体成核和畴壁运动所需要克服的退极化能和畴壁能,实现激光诱导畴反转。 相似文献
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用Raman散射研究了四方钽铌酸钾单晶的顺电 铁电结构相变,在相变时发现和分析了一个凝聚的软晶格振动模v5,它是产生于O2 O3键的对称弯曲振动。 相似文献
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用标量有限元方法计算了周期性极化的铌酸锂光波导中模折射率和模场分布,并在计算中引入铌酸锂晶体折射率与温度变化的关系,分析了准位相匹配铌酸锂波导倍频效率与极化反转光栅周期、基频光波长、波导器件温度等关系.理论分析与实验结果符合得很好.在此基础上,分析了波导制作参数与倍频效率、光栅周期与晶体温度,以及温度带宽与光栅通光方向长度等关系,进而对铌酸锂波导倍频器件进行优化设计.
关键词:
铌酸锂
光波导
准位相匹配
有限元 相似文献
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Electric permittivity * = ′ − i″ of nickel-hexammino nitrate (NHN) has been measured within the range of temperature from 9 to 300 K at a frequency of 8.8 GHz (X-band). It has been found that the phase transitions at Tk1 = 247 K and Tk2 = 90 K are discontinuous structural transitions between centrosymmetric phases, whereas the transition at Tc = 63 K is a continuous phase transition (glass?). 相似文献
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Bulk superconducting La2CuO4+δ single crystals are obtained by using electrochemical intercalation technique from the as-grown insulating samples. Oxidation is carried out by constant current I=10μA at temperature T=70℃ and room temperature, respectively. Structure and magnetic properties are studied by low-temperature X-ray diffraction and susceptibility measurements. A superconducting phase with Tc of 19K and δ-0.12 can be attributed to the formation of oxygen clusters. Room temperature oxidation is inhomogeneous: two superconducting phases with Tc1 of 24K and Tc2 of 8K and an antiferromagnetic phase are coexisting in the crystal. It is found that the appearance of Tc in this system has the "step" tendency. 相似文献
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Mitsuru Izumi Toshiaki Iwazumi Kunimitsu Uchinokura Ryozo Yoshizaki Etsuyuki Matsuura 《Solid State Communications》1984,51(4):191-194
The second-order structural phase transition was observed by X-ray diffraction technique in (NbSe4)3I. The transition temperature (Tc) was 274.2 K. No evidence of the formation of the charge-density wave was found out. Temperature dependence of the intensity of (0,5,12) reflection obeys the Landau theory of the second kind of phase transition near Tc. Temperature dependence of the integral breadth of (0,0,12) reflection indicates the effect of the soft-phonon mode below Tc. The existence of the structural phase transition, probably not associated with charge-density-wave formation, suggests the unique nature of (NbSe4)Z3I in the new series of compounds (MSe4)xI (M=Nb, Ta). 相似文献
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Raman scattering on single crystals of Eu3S4 does not show the allowed q=o phonon modes in the cubic phase and exhibits no new modes in the distorted low temperature phase (T<186 K). Above the Curie temperature Tc=3.8 K the scattering is dominated by a spin-disorder induced one-phonon density of states allowing for the observation of the zone boundary phonon breathing mode of the S2?ions. This mode does not show any anomaly near the charge order -disorder phase transition Tt=186 K. Temperature tunable spin fluctuations associated with the temperature activated Eu2+→Eu3+ electron hopping are detected in the scattering intensity, superimposed on the usual thermal spin disorder. 相似文献
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J.H.M. Mooy 《Solid State Communications》1981,39(12):1305-1309
Critical behaviour with dimensionality d = 2 has been observed for the 300 K antiferrodistortive phase transition in Al ur6(ClO4)3 and Ga ur6(ClO4)3 by means of the temperature dependence of the ESR parameter D. The systems exhibited d = 2 behaviour in the static critical behaviour for T<Tc?40 K for T>Tc + 40 K. From the ESR data including line width measurements the local order parameter relaxation rate ω1 has been obtained for various temperatures above Tc, with a lowest value of ω1 = 150 MHz at Tc + 15 K 相似文献
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Thermoreflectance of single-crystal HgCr2Se4 near the ferromagnetic-to-paramagnetic phase transition
The thermoreflectance of the ferromagnetic semiconductor HgCr2Se4 (Tc = 106 K) has been measured between 45 and 340 K in the photon energy range from 1.7 to 2.8 eV. The spectral line shape and the signal intensity behave critically near the magnetic phase transition. The optical transitions and the effect of magnetic ordering are discussed. 相似文献