Shlykov Alexander I, Baimuratov Anvar S, Baranov Alexander V, Fedorov Anatoly V, Rukhlenko Ivan D
Opt Express. 2017 Feb 20;25(4):3811-3825. doi: 10.1364/OE.25.003811.
Chiral molecules made of coupled achiral semiconductor nanocrystals, also known as quantum dots, show great promise for photonic applications owing to their prospective uses as configurable building blocks for optically active structures, materials, and devices. Here we present a simple model of optically active quantum-dot molecules, in which each of the quantum dots is assigned a dipole moment associated with the fundamental interband transition between the size-quantized states of its confined charge carriers. This model is used to analytically calculate the rotatory strengths of optical transitions occurring upon the excitation of chiral dimers, trimers, and tetramers of general configurations. The rotatory strengths of such quantum-dot molecules are found to exceed the typical rotatory strengths of chiral molecules by five to six orders of magnitude. We also study how the optical activity of quantum-dot molecules shows up in their circular dichroism spectra when the energy gap between the molecular states is much smaller than the states' lifetime, and maximize the strengths of the circular dichroism peaks by optimizing orientations of the quantum dots in the molecules. Our analytical results provide clear design guidelines for quantum-dot molecules and can prove useful in engineering optically active quantum-dot supercrystals and photonic devices.
由耦合的非手性半导体纳米晶体（也称为量子点）构成的手性分子，因其有望作为光学活性结构、材料和器件的可配置构建块，在光子应用中展现出巨大潜力。在此，我们提出一种光学活性量子点分子的简单模型，其中每个量子点都被赋予一个与受限电荷载流子尺寸量子化态之间的基本带间跃迁相关的偶极矩。该模型用于解析计算一般构型的手性二聚体、三聚体和四聚体激发时发生的光学跃迁的旋光强度。发现此类量子点分子的旋光强度比手性分子的典型旋光强度高出五到六个数量级。我们还研究了当分子态之间的能隙远小于态的寿命时，量子点分子的光学活性如何在其圆二色光谱中显现，并通过优化分子中量子点的取向来最大化圆二色峰的强度。我们的解析结果为量子点分子提供了清晰的设计指南，并可能在工程光学活性量子点超晶体和光子器件中发挥作用。
