Surface Effects and Pump-Probe Studies of Nanowire Waveguides

由氧化锌(ZnO)制成的纳米线和纳米棒是未来工作在近紫外区的光电子器件的重要组成部分。通过气相外延(VPE)技术，可以在不同的衬底上生长出光学质量优良、长度和直径可调的纳米棒。一种新的低温技术，它使用水化学生长(ACG)来制造大规模纳米棒阵列，提供了像使用柔性塑料衬底一样令人着迷的可能性。在本项目中，我们将系统分析ACG和VPE在不同衬底上生长的纳米棒的线性和非线性光学性质。重点将强调在透明衬底上使用纳米棒样品作为高效非线性光学器件的可能性，如倍频器。时间分辨测量将提供对脉冲光激发下ACG纳米棒中发生的微观过程的洞察，这在文献中到目前为止还没有涉及到。这些实验应该特别解释表面态对这种新材料的光学性质的作用和性质。最后，实验分析了利用ACG在金属层上生长纳米棒是否降低了这种器件的激光阈值，从而允许在光泵浦下进行有效的相干激光发射。

Nanowires and nanorods made of zincoxide (ZnO) are promising building blocks for future optoelectronic devices operating in the near-UV spectral region. By vapour-phase epitaxy (VPE) nanorods with excellent optical quality and carefully adjustable lengths and diameters can be grown on different substrates. A new low-temperature technique which uses aqueous chemical growth (ACG) for the fabrication of large-scale nanorod arrays provides fascinating possibilities like using flexible plastic substrates. In this project the linear and non-linear optical properties of nanorod ensembles grown by ACG and VPE on different substrates will be systematically analyzed. Emphasis will be put on the possibility of using nanorod samples on transparent substrates as highly efficient non-linear optical devices like frequency doublers. Time-resolved measurements will provide insight into the microscopic processes occurring in ACG nanorods under pulsed optical excitation which up to now have not been addressed in the literature. These experiments should especially explain the role and nature of surface states for the optical properties of this new kind of material. Finally, it will be experimentally analyzed if the growth of nanorods using ACG on metallic layers decreases the lasing threshold in such devices thus allowing for efficient coherent laser emission under optical pumping.