Second harmonic generation with plasmonic metasurfaces: direct comparison of electric and magnetic resonances

TL;DR

This study compares electric and magnetic resonances in plasmonic metasurfaces to determine their individual contributions to second harmonic generation enhancement, revealing electric resonance's greater impact.

Contribution

It presents an experimental metasurface design allowing independent tuning of electrical and magnetic resonances for direct comparison.

Findings

Magnetic resonance provides 50% less SHG enhancement than electric resonance.

Aligning both resonances in frequency yields a conversion efficiency of 1.32 x 10^(-10).

The metasurface enables separate analysis of electric and magnetic resonance effects.

Abstract

Plasmonic resonances in metallic nanostructures have been shown to drastically enhance local electromagnetic fields, and thereby increase the efficiency of nonlinear optical phenomena, such as second harmonic generation (SHG). While it has been experimentally observed that enhanced fields can significantly boost SHG, to date it proved difficult to probe electrical and magnetic resonances in one and the same nanostructure. This however is necessary to directly compare relative contributions of electrical and magnetic components of SHG enhancement. In this paper we report an experimental study of a metasurface capable of providing electrical and magnetic resonant SHG enhancement for TM polarization. Our metasurface could be engineered such that the peak frequencies of electrical and magnetic resonances could be adjusted independently. We used this feature to distinguish their relative contributions. Experimentally it was observed that the magnetic resonance provides only 50% as much enhancement to SHG as compared to the electric resonance. In addition aligning both resonances in frequency results in conversion efficiency of 1.32 x 10^(-10).