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Coherent Phonon Quantum Dynamics in Semiconductor Nanostructures

半导体纳米结构中的相干声子量子动力学

基本信息

批准号：
09450025
负责人：
WRIGHT Oliver B.
金额：
$ 9.09万
依托单位：
HOKKAIDO 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-09450025/
关键词：
Ultrafast Semiconductor Laser Phonon Ultrasound Superlattice Reflectance Surface

项目摘要

The main aim of this study is to extend our knowledge of ultrafast acoustic phonon generation using femtosecond light pulses to basic semiconducting materials and nanostructures. We use tightly focused excitation and probe light beams a few microns in diameter to allow the detection of coherent phonons with -1 mum lateral spatial resolution and sub-picosecond time resolution. In order to do this we have developed an ultrafast Sagnac interferometer for measurements at normal incidence.The following studies were carried out :1) Design and construction of a Sagnac interferometer for detection of coherent acoustic phonons on picosecond time scales. The design is particularly convenient for normal incidence measurements and is common path, rendering it immune to acoustic and thermal parasitic fluctuations.2) Generation and detection of longitudinal coherent acoustic phonons in bulk GaAs (100). Above band-gap excitation and probe optical beams were incident from the same side of the sample. … More The effect of coherent phonon pulses propagating into the bulk was detected.3) Generation and detection of longitudinal coherent acoustic phonons in ultrathin (<1 mum) GaAs (100) film (thickness 50 nm) on a Al_<0.3>Ga_<0.7>As (100) substrate film.(- 5 mum in thickness). Above band-gap excitation and probe optical beams were incident from opposite sides of the sample, allowing us to temporally separate phonon pulse signals from spurious thermal and purely electronic contributions to the signal.4) Generation and detection of coherent acoustic phonons in periodic GaAs/AlAs superlattices. Superlattices with atomic order repeat lengths were probed. Selective excitation of the GaAs was achieved by tuning the pump beam to around 830 nm. A new excitation configuration, in which the superlattice was cleaved at right angles to the normal direction, was attempted. Signals due to the propagation of longitudinal acoustic phonons in the in-plane direction were observed.In addition, theoretical work on metals carried out in parallel has allowed a first analytical treatment of the nonequilibrium relaxation of a free electron gas. Further work is needed to extend the technique to a wider variety of semiconductors and to higher frequency acoustic generation. up to - 10 THz. Less

本研究的主要目的是扩展我们的知识超快声学声子产生使用飞秒光脉冲的基本半导体材料和纳米结构。我们使用紧密聚焦的激发和探测光束直径为几微米，允许检测相干声子与-1妈妈横向空间分辨率和亚皮秒时间分辨率。为了实现这一目标，我们研制了一台用于正入射测量的超快Sagnac干涉仪，主要进行了以下研究：1）设计并制作了一台用于皮秒时间尺度相干声学声子探测的Sagnac干涉仪。该设计对于正入射测量特别方便，并且是公共路径，使其免受声学和热寄生波动的影响。2）体GaAs（100）中纵向相干声学声子的产生和检测。上述带隙激发光束和探测光束从样品的同一侧入射。 ...更多信息 3）在Al_ Ga_ As（100）衬底薄膜上的GaAs（<1 μ m）薄膜（厚度50 nm）中纵向相干声学声子的产生和检测<0.3><0.7>。（厚度约为5 μ m）。上述带隙激发和探测光束从样品的相对侧入射，使我们能够在时间上将声子脉冲信号与对信号的寄生热和纯电子贡献分离。4）周期性GaAs/AlAs超晶格中相干声学声子的产生和检测。探索了具有原子有序重复长度的超晶格。GaAs的选择性激发通过将泵浦光调谐到830 nm左右来实现。尝试了一种新的激发构型，其中超晶格以与法线方向成直角的方式裂开。由于纵向声学声子在面内方向的传播信号被observed.In此外，平行进行的金属的理论工作，允许自由电子气的非平衡弛豫的第一个分析处理。需要进一步的工作来扩展该技术到更广泛的半导体和更高频率的声学产生。高达-10THz。少