Comparison of second harmonic generation from cross-polarized double-resonant metasurfaces on single crystals of Au

Yusuf B Habibullah,Teruya Ishihara

doi:10.1515/nanoph-2021-0677

Abstract

Abstract Second harmonic generation (SHG) from metasurfaces consisting of square array of split ring, heptagon and triangle cross-polarized double resonant resonators, is investigated both experimentally and numerically. The structures are fabricated on single crystalline Au plates using Focused Ion Beam technique. Array of the triangular structure exhibits most efficient SHG. Experimental observation is explained reasonably well by theoretical evaluation of SHG using the overlapping integral of nonlinear polarization and the microscopic field distribution on the metal surface at the SHG frequency taking phase relation between the two fields into account.

Highlights

Second harmonic generation (SHG) is one of the 2nd order optical nonlinear effects, where two photons with angular frequency ω are combined to generate one with 2ω
Second harmonic generation (SHG) from metasurfaces consisting of square array of split ring, heptagon and triangle cross-polarized double resonant resonators, is investigated both experimentally and numerically
As the light intensity from optical parametric amplifier (OPA) varies for different wavelengths, we normalize the SHG intensity based on the square dependence

Summary

Introduction

Second harmonic generation (SHG) is one of the 2nd order optical nonlinear effects, where two photons with angular frequency ω are combined to generate one with 2ω. As it is essential to break the inversion symmetry, artificial structures were designed to demonstrate SHG from noncenytrosymmetric materials [6,7,8,9,10,11,12]. Later the same group showed that its complementary structure (SRR hole in metallic film) with no magnetic resonance had similar intensity of SHG [14]. By comparing SHG intensity from SRR metamaterials with different aspect ratios, they show that metamaterials are free from the limit of so-called Miller’s rule [16, 17], which predicts a nonlinear optical susceptibility of a material from its linear ones. Note that by using the overlap integral, it is naturally understood that SHG vanishes unless overall inversion symmetry is broken, irrespective of type of interactions. SHG from complementary structures was discussed in [19]

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Discussion

Conclusion