Time-domain coherent phonon spectroscopy and dynamics of structural change

我们已经建立了一个系统来测量固体中的高频相干分布，使用钛：蓝宝石脉冲激光器与~ 10个生育周期。构造系统的特征是根据各种材料和SHG信号中的相干声子的测量而进行的。16 fs的脉冲持续时间和10-7顺序的反射率变化（ΔR/R）已经出现。使用这个系统，我们可以用良好的S/N比率来衡量相干的密码，这是如此巨大的观察到它们。我们在半金属、超晶格、半导体、半导体和半导体以及半导体和材料中测试了一致性的耳机。我们研究的结果如下：（1）我们从拉曼和相干声子的比较中找到了一个比较，即相干声子的年份主要由能量放松控制，而纯减相的贡献在Bi中很小。（二） Fo ... More r Bi/Sb超晶格，我们有第一个被确认为常量层、双Sb接口模式和折叠的纵向声学模式的可见相干振荡。“计算器中相干折叠模式的观察频率的偏移，在非常薄的Bi层中表现出弹性异常现象。”（3）我们使用空间调制过滤器生产了脉冲列车，并实验性地证明了对控制相干phonons的振幅和指定的phonon模式的选择性异常是可能的Bi/Sb混合晶体。（4）我们第一次观察到GaAs和InP中的上和下分支的相干LO-phonon等离子体偶联模式。我们还确定了载波密度对双模式变化的依赖，并讨论了动力学。（5）折叠的纵向声学耳机的相干分布在GaAs-Alas超晶格中。我们已经为相干的声子提供了线索，以帮助理解一代人和检测机制。（6） We have observed coherent phonons in materials which undergo phase transitions in VイイD22イイD2OイイD23イイD2，イイD24イイD211イイD2 and GeTe and obtained much information on the mManagement isms of the generation and relaxation of the coherent phonons。Less（低）

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