Generalized nonlocal optical response in linear and nonlinear optical absorption coefficients of a semiconductor quantum dot coupled to a noble metal nanoparticle.

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.