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Time-domain coherent phonon spectroscopy and dynamics of structural change

时域相干声子光谱和结构变化动力学

基本信息

批准号：
09440119
负责人：
NAKASHIMA Shin-ichi
金额：
$ 9.28万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09440119/
关键词：
coherent phonons femotosecond pulse laser plasmon LO-phonon coupled mode ultra fast dynamics semiconductor semimatal semiconductor superlattice フェムト秒パルスレーザー

项目摘要

We have constructed a system for measurement of high frequency coherent oscillations of phonons and electrons in solids, using Ti : sapphire pulse lasers with 〜 ten femtosecond duration. The characteristics of the constructed system has been evaluated by measurements of the coherent phonons in various materials and the SHG signals. The pulse duration of 16fs and reflectivity change (ΔR/R) of the order of 10-7 have been obtained. Using this system we were able to measure the coherent phonons in Ge with a good S/N ratio, which was so far difficult to observe them. We have examined coherent phonons in semimetals, superlattices, semiconductors, semiconductor- and semimetal-and materials which undergo phase transition.The results of our studies are as follows :(1) We have found from a comparison of the Raman and coherent phonon spectra that the decay of the coherent phonons is mainly governed by the energy relaxation and that the contribution of the pure dephasing is very small in Bi.(2) Fo … More r Bi/Sb superlattices, we have first observed coherent oscillations of optical modes confined in the constituent layers, Bi-Sb interface modes, folded longitudinal acoustic modes. The deviation of the observed frequency of the coherent folded modes from the calculated ones is attributed to elastic anomaly in very thin Bi layers.(3) We have produced pulse trains using spatial modulation filters and a grating pair and experimentally proved that the control of the amplitude of the coherent phonons and the selective excitation of specified phonon modes are possible for Bi/Sb mixed crystals.(4) We have first observed both the upper and lower branches of coherent LO-phonon plasmon coupled modes in GaAs and InP. We also determined carrier density dependence of coupled-mode decays and discussed the dynamics.(5) The coherent oscillations of folded longitudinal acoustic phonons are observed in GaAs-AlAs superlattices. We have obtained a clue for understanding the generation and detection mechanisms for the coherent phonons.(6) We have observed coherent phonons in materials which undergo phase transitions in VィイD22ィエD2OィイD23ィエD2, η-MoィイD24ィエD2OィイD211ィエD2 and GeTe and obtained much information on the mechanisms of the generation and relaxation of the coherent phonons. Less

我们利用钛宝石脉冲激光器，建立了一个测量固体中声子和电子高频相干振荡的系统。通过测量不同材料中的相干声子和倍频信号，对所构建的系统的特性进行了评价。获得了16 fs的脉冲宽度和10-7量级的反射率变化（ΔR/R）。利用这个系统，我们能够测量Ge中的相干声子，具有良好的S/N比，这是迄今为止难以观察到的。我们研究了半金属、超晶格、半导体、半导体和半金属以及相变材料中的相干声子，结果如下：（1）从拉曼谱和相干声子谱的比较中发现，相干声子的衰减主要受能量弛豫的控制，纯退相对Bi的贡献很小。(2)Fo ...更多信息在Bi/Sb超晶格中，我们首次观察到了束缚在组成层中的光学模、Bi-Sb界面模、折叠纵声模的相干振荡。相干折叠模频率的观测值与计算值的偏差归因于极薄Bi层中的弹性异常。(3)我们用空间调制滤波器和光栅对产生了脉冲序列，并从实验上证明了Bi/Sb混晶中相干声子的振幅控制和特定声子模的选择性激发是可能的。(4)我们首次在GaAs和InP中观察到了相干LO-声子等离激元耦合模的上、下分支。我们还确定了耦合模衰减的载流子密度依赖性，并讨论了动力学。(5)在GaAs-AlAs超晶格中观察到折叠纵声声子的相干振荡。我们获得了理解相干声子的产生和检测机制的线索。(6)我们在V_（22）O_（23）O_（24）O_（21）O_（23）O_（24）O_（21）O_（24）O_少