Polarization dependence of second harmonic generation from plasmonic nanoprism arrays

K Y Raygoza-Sánchez,P Segovia,I Rocha-Mendoza,N Michieli,T Cesca,A V Zayats,A V Krasavin,R Rangel-Rojo,G Marino,G Mattei

doi:10.1038/s41598-019-47970-3

Abstract

The second order nonlinear optical response of gold nanoprisms arrays is investigated by means of second harmonic generation (SHG) experiments and simulations. The polarization dependence of the nonlinear response exhibits a 6-fold symmetry, attributed to the local field enhancement through the excitation of the surface plasmon resonances in bow-tie nanoantennas forming the arrays. Experiments show that for polarization of the input light producing excitation of the plasmonic resonances in the bow-tie nanoantennas, the SHG signal is enhanced; this despite the fact that the linear absorption spectrum is not dependent on polarization. The results are confirmed by electrodynamic simulations which demonstrate that SHG is also determined by the local field distribution in the nanoarrays. Moreover, the maximum of SHG intensity is observed at slightly off-resonance excitation, as implemented in the experiments, showing a close relation between the polarization dependence and the structure of the material, additionally revealing the importance of the presence of non-normal electric field components as under focused beam and oblique illumination.

Highlights

Nanocomposite materials, containing dielectric, semiconductor or metallic nanoparticles with typical sizes in the 1–100 nm range, have attracted considerable interest for their optical properties, and potential applications, such as optical signal processing[1], and chemical or biological sensing[2,3,4]
These nanocomposites present interfaces that break the symmetry, and allow the observation of second-order nonlinear optical effects such as second harmonic generation (SHG). These are usually surface effects, where the contribution comes only from a very thin layer of material at either side of the interface. Given their small dimensions, this can include most of its bulk, and again, local field enhancement can boost the SHG signal produced in these materials to significant levels[12]
The polarization dependence of the SHG was measured, with the polarization azimuthal angle defined in relation to the laboratory reference frame as shown in Fig. 1b, i.e. the 0° angle corresponds to the polarization direction along the x-axis

Summary

Introduction

Nanocomposite materials, containing dielectric, semiconductor or metallic nanoparticles with typical sizes in the 1–100 nm range, have attracted considerable interest for their optical properties, and potential applications, such as optical signal processing[1], and chemical or biological sensing[2,3,4]. In this article we present an experimental and numerical study of SHG from a honeycomb array of Au nanoprisms and its relation to the polarization of the fundamental light.

Results

Conclusion