Electron-LO-Phonon Quantum Kinetics in Wide-Gap II-VI Nanostructures with Strong Confinement

本文研究了II-VI量子阱和量子线中激子与纵向光学声子之间的相干耦合。利用亚20飞秒的超短脉冲，可以在激发时间短于lo -声子振荡周期的条件下探测耦合。除了研究强库仑相互作用和大电子- lo -声子耦合之间的内在性质和干涉现象外，所提出的具有强约束的宽间隙II-VI纳米结构还可以使激子结合能在lo -声子能量之上进行独特的调谐。结果可以观察到新的量子动力学效应。这些研究将作为扩展量子动力学模型的关键测试，并将有助于提高对极性准二维和准一维纳米结构中相干电子- lo -声子散射的理解和解释。研究生将获得与前沿技术的基础实验技术的经验。这种培训将为他们在学术界、工业界和政府的一系列职业生涯做好准备。这项工作是针对利用超短飞秒光脉冲研究宽带隙II-VI半导体纳米结构中电子激发和晶格振动之间的相干耦合。在这些实验中，光激发时间短于晶格振荡周期，因此在激发后的早期电子散射过程可以视为干涉现象。提出的研究将揭示新的相干效应，并有助于提高对可逆和不可逆电子散射界面上的光激发半导体的理解和解释。它将作为适用于这些纳米结构的扩展理论模型的关键测试。实验结果将对理论研究产生强烈的影响，对信息技术也具有重要意义。该课程的学生接受超快相干光学和半导体物理方面的严格培训，为他们在学术界或工业界的职业生涯做好准备

This research investigates coherent coupling between excitons and longitudinal optical (LO)-phonons in II-VI quantum wells and quantum wires. Using ultrashort sub-20-femtosecond pulses, the coupling can be probed under conditions where the excitation time is shorter than the LO-phonon oscillation period. In addition to studying intrinsic properties and interference phenomena between strong Coulomb-interaction and large electron-LO-phonon coupling, the proposed wide-gap II-VI nanostructures with strong confinement also may allow unique tuning of the exciton binding energy above the LO-phonon energy. As a result novel quantum kinetic effects may be observed. The investigations will serve as crucial tests of extended quantum kinetic models and will contribute to an improved understanding and interpretation of the coherent electron-LO-phonon scattering in polar quasi-two and quasi-one dimensional nanostructures. Graduate students will gain experience in fundamental experimental techniques with cutting edge technology. This training will prepare them for a range of careers in academe, industry and government. %%%This work is directed at the study of coherent coupling between electronic excitations and lattice vibrations in wide-band-gap II-VI semiconductor nanostructures utilizing ultrashort femtosecond light pulses. In these experiments the optical excitation time is shorter than the lattice oscillation period so that at early times after excitation electron scattering processes can be treated as interference phenomena. The proposed research will uncover novel coherent effects and contribute to an improved understanding and interpretation of optically excited semiconductors at the interface between reversible and irreversible electron scattering. It will serve as a crucial test of extended theoretical models appropriate for these nanostructures. The experimental results will have a strong impact on theoretical research and will also have importance for information technologies. Students in this program receive rigorous training in ultrafast coherent optics and semiconductor physics, which prepares them for careers in academia or industry.***