Hybrid plasmonic - all-dielectric nanodimers for second-harmonic generation

Hybrid nanoscale structures which combine properties of dielectric and plasmonic components, currently attract a lot of attention. Such structures would be particularly useful to combine nonlinear optical properties of... [ view full abstract ]

Hybrid nanoscale structures which combine properties of dielectric and plasmonic components, currently attract a lot of attention. Such structures would be particularly useful to combine nonlinear optical properties of dielectrics with linear plasmon resonances in order to enhance low-intensity signals at the nanoscale (see Fig. 1). Nowadays, it is feasible to fabricate nanodimers with a single material using the standard microelectronics techniques, but constructing hybrid nanodimers consisting of two dissimilar materials is still a challenge. Here, we demonstrate a template assisted colloidal assembly technique to fabricate nonlinear hybrid nanodimers composed of 80 nm gold (Au) and 100 nm BaTiO₃ nanoparticles. The dark-field optical images of isolated gold nanoparticles and after assembly with BaTiO₃ show a change of the scattering spectrum due to the effective nanoparticle interaction. The hybrid nanostructures benefit from the surface plasmon resonance of the Au nanoparticles at the second-harmonic wavelength to enhance a nonlinear signal originated from the BaTiO₃ nanoparticles. We measure a nonlinear signal from the hybrid nanodimers and demonstrate up to 10 times enhancement in comparison to isolated BaTiO₃ particles. The maximal enhancement is observed when the second-harmonic wavelength coincides with the resonance of localized surface plasmons of gold nanoparticle (see Fig. 2). The performed numerical calculations of both linear and nonlinear spectra of the hybrid nanodimer reveal that the Au particle in the dimer operates as a nanoantenna enhancing the emission at the second-harmonic wavelength. Moreover, we discuss the efficiency of nonlinear signal generation when the hybridization plasmonic and all-dielectric modes takes place. 

The work has been supported by the Russian Ministry of Science and Education (project #RFMEFI58416X0018). The authors also acknowledge the Swiss National Science Foundation (SNSF) (grants IZLRZ2_163916 and PP00P2_150609) and the Australian Research Council.