Abstract
We investigate the influence of localized and propagating surface plasmons on third harmonic generation from rectangular apertures in metal films. We designed optimal aperture array structures by using finite-difference time-domain simulations with nonlinear scattering theory. From this design space, we fabricated and measured the third harmonic in the region of maximal performance. We find the highest third harmonic conversion efficiency when the localized resonance is tuned to the fundamental wavelength and the propagating (Bragg) resonance is tuned to the third harmonic; this is 2.5 times larger than the case where the both localized and propagating are tuned to the fundamental wavelength. The two remaining configurations where also investigated with much lower conversion efficiency. When the Bragg resonance is tuned to the third harmonic, directivity improves the collection of third harmonic emission. On the other hand, due to the inherent absorption of gold at the third harmonic, tuning the localized surface plasmon resonance to the third harmonic is less beneficial. All cases showed quantitative agreement with the original theoretical analysis. This work points towards an optimal design criterion for harmonic generation from thin plasmonic metasurfaces.
Highlights
Metasurfaces are of interest for nonlinear optics to achieve functionality in a thin layer, for applications including wavelength conversion [1,2], switching [1,3,4] and near-field light sources [5,6]
We investigate the influence of localized and propagating surface plasmons on third harmonic generation from rectangular apertures in metal films
This work points towards an optimal design criterion for harmonic generation from thin plasmonic metasurfaces
Summary
Metasurfaces are of interest for nonlinear optics to achieve functionality in a thin layer, for applications including wavelength conversion [1,2], switching [1,3,4] and near-field light sources (imaging) [5,6]. Among these surfaces, aperture-based structures in metal films are promising because they efficiently remove heat and localize the electromagnetic field [7,8,9]. We investigate the optimal combination of LSP and SPP resonances to maximize conversion efficiency in third harmonic generation (THG) from nanoapertures in a gold film. Our experimental results agree well with nonlinear scattering theory using finite-difference time-domain (FDTD) simulations
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