Time-domain coherent phonon spectroscopy and dynamics of structural change

我们已经建立了一个系统，为高频率coherent oscillations of phonons和electrons in solids, using Ti：sapphire pulse lasers with ten femtosecond duration. The characteristics of The constructed systemhas been evaluated by方法of the coherent phonons in various materials and the SHGsignals. The pulse duration of 16fs and flectivity change （ΔR/R） of The order of 10-7 have been使用这个系统，我们可以measure the coherent phonons in Ge with a good S/Nratio，我们已经在semimetals，这是如此遥远的差异来观察他们。superlattices, semiconductors,semiconductor- and semimetal-and materials which undergo phase transition.The results of our studies(1)我们已经发现了Raman and coherent phonon spectra that comparison of the Raman and coherent phonon spectra thatthe decay of the coherent phonons is mainly governed by the energy relaxation and that thecontribution of the pure dephasing is very small in Bi.(2)r Bi/Sb superlattices，我们已经有了第一个监测coherent oscillations of optical modes confined in the constituent layersBi-Sb接口模式folded longitudinal acoustic modes. The deviation of The observed frequency of The coherent folded(3)我们有一个习惯的东西，是在其他方面的贡献。produced pulse trains using spatial modulation filters and a grating pair and experimentally provedthe amplitude of the coherent phonons and the selective excitation of specifiedphonon modes are possible for Bi/Sb mixed crystals.(4)我们有第一次观察both the upper andlower branches of coherent LO-phonon plasmon coupled modes in GaAs and InP. We also determinedcarrier density dependence of coupled-mode decays and discussed the dynamics.(5) the coherentoscillations of folded longitudinal acoustic phonons are observed in GaAs-AlAs superlattices. Wehave obtained a clue for the generation and detection mechanisms for the coherent(6)我们已经观察了相关的phonons in materials which undergo phase transitions in materialsD22 D2O D23 D2徐-Mo D24 D2O D211 D2 and GeTe and obtained much information on the mechanisms of the generationand relaxation of the coherent phonons. Less

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