尺寸依赖的半导体量子点非线性光学性质研究

To explore the origin of the quantum dots' (QDs’) size-dependent nonlinear optical (NLO) property is a challenging task and has great significance to describe the surface structures of these colloidal nanostructures as well as to improve the performance of QDs’ devices. Once bound in an atom, the exciton's motion becomes highly confied and semiconductor QD's optical nonlinearity increases sensitively with the size of QD decreases. However, in contrast, recent studies observed the decrease in nonlinear absorption in QDs. To explore the origin of the QDs’ surface-dependent nonlinear optical (NLO) process is a challenging task. The experimental and theoretical studies clearly demonstrate the effect of the surface states on the steady-state and time-resolved PL spectra of colloidal quantum dots (QDs) in multifarious situations, but comparatively little is concerned about the two-photon absorption and refraction involved in the surface traps. In this project, the surface-dependent NLO absorption and refraction of the QDs will be investigated by Z-scan technology and other nonlinear optical measurements. The QDs will be synthesized by chemically colloidal method whose sizes will be controlled by reactive conditions, and the QDs' sizes and surface states will be characterized by transmission electron microscopy (TEM)/ high-resolution transmission electron microscopy (HRTEM)/ X-ray diffraction (XRD) and absorption/fluorescence spectrum. This work will shed light on comprehending the physical mechanism of the exciton states and size-dependent optical nonlinearity of semiconductor QDs.

研究量子点尺寸依赖的非线性光学过程的机制对描述激子状态和提高量子点器件性能都非常重要。激子受限时，量子点的光学非线性随尺寸减小而增强。而近来的研究发现，量子点的光学非线性随尺寸的减小而减小，可见研究尺寸依赖的量子点非线性光学性质是一项有挑战性的工作。由于有大的表面积-体积比，量子点的表面态在非线性光学过程中起重要的作用，然而很少被关心涉及。本项目中拟通过控制反应物配比和反应条件，如温度、时间等，合成尺寸范围涵盖强限域和中等限域的量子点。用形貌、结构、光谱和动力学等多种手段表征量子点尺寸和表面结构，用Z扫描等多种非线性技术测量尺寸依赖的量子点非线性光学性质，在充分考虑表面态作用的情况下，理论拟合结合实验分析机制。为深入揭示量子点激子态、非线性光学机制与表面结构提供重要实验手段和理论依据。

研究量子点尺寸依赖的非线性光学过程的机制对描述激子状态和提高量子点器件性能都非常重要。激子受限时，量子点的光学非线性随尺寸减小而增强。而近来的研究发现，量子点的光学非线性随尺寸的减小而减小，可见研究尺寸依赖的量子点非线性光学性质是一项有挑战性的工作。由于有大的表面积-体积比，量子点的表面态在非线性光学过程中起重要的作用，然而很少被关心涉及。本项目中拟通过控制反应物配比和反应条件，如温度、时间等，合成尺寸范围涵盖强限域和中等限域的量子点。用形貌、结构、光谱等多种手段表征量子点尺寸和表面结构，用Z扫描等多种非线性技术测量尺寸依赖的量子点非线性光学性质，在充分考虑表面态作用的情况下，理论拟合结合实验分析机制。为深入揭示量子点激子态、非线性光学机制与表面结构提供重要实验手段和理论依据。