Boosting nonlinearity of metasurfaces through decrease in number of particles

Description

Metal nanoparticles demonstrate unique optical properties dominantly due to localized surface plasmon resonances (LSPRs). In the case of metasurfaces, the nanoparticles are arranged in the array and LSPRs are modified by coupling between the particles, giving rise to surface lattice resonances (SLRs). Both types of resonances can lead to local-field enhancement and thereby boost nonlinear optical effects. For the specific case of second-harmonic generation (SHG) the sample needs to be also non-centrosymmetric, which can be fulfilled by using V-shaped nanoparticles. Increasing the number of particles typically increases the optical density, which should increase the nonlinear response with the square of the particle density. This approach, however, has its limitations because, when the particles are too close to each other, the quality of the LSPRs decreases leading to an effect opposite to the desired. We will show the counterintuitive effect that the nonlinear response can be enhanced by reducing the number of particles in the array. By removing every other particle from the array we change the lattice constant, which allows for SLR of higher quality than LSPR. This, in turns leads to significantly stronger enhancement of the SHG, compensating for the reduction in the number density of particles.

Period	2018
Event title	SPIE photonics Europe
Event type	Conference
Degree of Recognition	International