Liu Guanghui, Liu Yecai, Chen Gengyan, Wu Feng, Zheng Yunbao, Guo Kangxian, Lu Liangliang
Opt Express. 2025 Mar 10;33(5):9523-9538. doi: 10.1364/OE.544893.
Hybrid nanostructures composed of a semiconductor quantum dot (SQD) and a metal nanoparticle (MNP) are appealing candidates for the investigation of exotic optoelectronic properties and their potential applications due to the coupling between exciton in SQD and surface plasmon in MNP. In most studies on the SQD-MNP hybrid nanostructures, the conventional local response approximation (LRA) is deployed to model the MNP, but the classical LRA fails to interpret experimental results such as the size-dependent frequency shifts and damping of surface plasmon in quantum-sized MNP for decreasing the MNP size. The generalized nonlocal optical response (GNOR) model is a generalization and an extension of the hydrodynamic Drude model, and it can explain surprisingly well the aforementioned experimental results of noble MNP. In this paper, we provide a comparison of the linear and nonlinear optical absorption coefficients (OACs) of the hybridized SQD based on the GNOR model and the LRA model, where silver MNP is adopted. In contrast to the LRA model, the GNOR model not only suggests an enhancement in the peak values of the linear and nonlinear OACs of the hybridized SQD but also causes a blue shift and a smaller spectral linewidth in the linear and nonlinear OACs of the hybridized SQD, the feature for which is more pronounced for small SQD-MNP surface distance. Our work also demonstrates the convergence of the GNOR model to the LRA model for the linear and nonlinear OACs of the hybridized SQD by increasing the SQD-MNP surface distance or increasing the MNP radius. Moreover, the linear and nonlinear OACs of the hybridized SQD as a function of the distance are discussed based on the two models, thereby allowing us to find stronger linear and nonlinear OACs. In addition, the impact of the incident optical intensity on the total OACs of the hybridized SQD under strong and weak exciton-plasmon couplings is discussed based on the two models. Our findings pave the way for optimized designs of linear and nonlinear nanophotonic devices with small footprints by utilizing such hybrid nanostructure made of SQD and quantum-sized noble MNP.
由半导体量子点（SQD）和金属纳米颗粒（MNP）组成的混合纳米结构，由于SQD中的激子与MNP中的表面等离子体之间的耦合，是研究奇异光电特性及其潜在应用的有吸引力的候选材料。在大多数关于SQD-MNP混合纳米结构的研究中，传统的局部响应近似（LRA）被用于对MNP进行建模，但经典的LRA无法解释实验结果，比如量子尺寸的MNP中表面等离子体的尺寸依赖性频移和阻尼，随着MNP尺寸减小。广义非局部光学响应（GNOR）模型是流体动力学德鲁德模型的推广和扩展，它能很好地解释上述贵金属MNP的实验结果。在本文中，我们基于GNOR模型和LRA模型，对采用银MNP的杂交SQD的线性和非线性光学吸收系数（OAC）进行了比较。与LRA模型相比，GNOR模型不仅表明杂交SQD的线性和非线性OAC峰值增强，而且导致杂交SQD的线性和非线性OAC出现蓝移和更小的谱线宽度，对于小的SQD-MNP表面距离，这一特征更为明显。我们的工作还表明，通过增加SQD-MNP表面距离或增加MNP半径，GNOR模型对于杂交SQD的线性和非线性OAC会收敛到LRA模型。此外，基于这两个模型讨论了杂交SQD的线性和非线性OAC作为距离的函数，从而使我们能够找到更强的线性和非线性OAC。此外，基于这两个模型讨论了在强和弱激子-等离子体耦合下入射光强度对杂交SQD总OAC的影响。我们的研究结果为利用由SQD和量子尺寸的贵金属MNP制成的这种混合纳米结构，优化设计具有小尺寸的线性和非线性纳米光子器件铺平了道路。
