Fine-tuning of plasmonics by Au@AuY/Au core-shell nanoparticle monolayer for enhancement of third-order nonlinearity

The manipulation of plasmonics on noble metal nanoparticles (NPs) is of great interest in developing nonlinear photonic devices, such as all-optical switches and frequency combs. An Au@AuY-core/Au-shell nanoparticle (Au@AuY/Au NP) monolayer is proposed for the fine-tuning of plasmonics and enhanced third-order nonline-arity. Based on the different thermodynamic mechanisms of Au and Y ions, the compact Au@AuY/Au core-shell architectures are designed and surface-modified in fused silica (SiO2) with enhanced free electron density, mobility, and quantum size effect. The flexible modulation of plasmonics is realized, resulting in significant absorption enhancement (165% for interband absorption and 38% for free electron absorption, respectively) and fine-tuning of the localized surface plasma resonance (LSPR) band. In addition, the physical mechanism is investigated by density functional theory (DFT) and Mie theory, which reveals a transition from size-independence to size-dependence of LSPR owing to the synergistic effect of multiple physical factors such as free electron density and mobility. With the above advantages, the third-order nonlinearity is enhanced by 4.4 times compared with traditional Au NPs. It indicates the significant potential of Au@AuY/Au core-shell NP monolayer in the performance improvement of nonlinear photonic devices.

Automated summary

By designing the structure of metal nanoparticles, the manipulation of surface plasmonics can be achieved, resulting in enhanced absorption and fine-tuning of localized surface plasmon resonance band. This offers potential for improving the performance of nonlinear photonic devices.