Second‐Harmonic Generation from Hyperbolic Plasmonic Nanorod Metamaterial Slab

Abstract

Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. In this work, second‐harmonic generation in a hyperbolic metamaterial due to a free‐electron nonlinear response of a plasmonic component of the metamaterial is studied. It is shown that owing to a rich modal structure of an anisotropic plasmonic metamaterial slab, the overlap of fundamental and second‐harmonic modes results in the broadband enhancement of radiated second‐harmonic intensity by up to 2 orders of magnitude for TM‐ and TE‐polarized fundamental light, compared to a smooth Au film under TM‐polarised illumination. Compared to the radiated second‐harmonic intensity from a bulk LiNbO3 nonlinear crystal of the same thickness, the SHG intensity from a metamaterial slab may be up to 2 orders of magnitude higher at the certain metamaterial resonances. The results open up possibilities to design tuneable frequency‐doubling integratable metamaterial with the goal to overcome limitations associated with classical phase matching conditions in thick nonlinear crystals.

Structural second-order nonlinearity in plasmonic metamaterials

“…Sample A exhibits the effective plasma frequency at around λ 0 ≃ 1500 nm, while sample B operates in hyperbolic regime throughout visible and infrared spectral ranges. The linear reflection spectra of the composites are typical of anisotropic metamaterials, showing resonances due to the Fabry-Perot modes of the metamaterial slab [23,28]. The measured spectra correspond well to the numerical models for both the full-wave solutions of the Maxwell's equations using finiteelement method (FEM) [31] and the transfer matrix formalism that approximates metamaterials as homogeneous layers with anisotropic permittivity given by Eq.…”

“…At the same time, SHG signal generated by sample B (Fig. 3) exhibits pronounced maxima associated with excitation of the metamaterial slab modes [28] for both pand s-polarized excitation. Interestingly, the SHG intensity from sample B under s-polarized excitation is approximately four times stronger than under p-polarized pump, indicating the important role of local fields inside the metamaterial, as was observed previously for the nanoparticle composites [33].…”

“…Importantly, components of the effective permittivity tensor ϵ ⊥ and ϵ zz can be of different signs (Fig. 1), tuning the nanorod composite between anisotropic dielectric, epsilon near zero (ENZ) media, and a unique "hyperbolic metamaterial," which enables propagation of waveguided modes with subwavelength light confinement that in turn enhance light-matter interactions in the metamaterial [10,12,23,28].…”

Free‐electron Optical Nonlinearities in Plasmonic Nanostructures: A Review of the Hydrodynamic Description

“…In the other type of metamaterials, hyperbolic plasmonic metamaterials formed by arrays of vertically standing metallic nanorods, coupling between the nanorods results in the formation of waveguided modes which have significant influence on the SHG spectrum and efficiency, being an analogue of the double‐resonant condition . The hyperbolic nature of the metamaterial provides an abundant spectrum of the waveguided modes with multiple resonances in infrared and visible spectral ranges.…”

Spontaneous photon-pair generation from a dielectric nanoantenna

“…For a long time, plasmonic nanoantennas have been considered as a favorable platform for enhancing single-photon emission (14,15) and nonlinear interactions (16)(17)(18)(19)(20). However, the limited volume of the plasmonic modes, the losses and the centrosymmetric nature of plasmonic materials, result in a relatively low second order nonlinear conversion efficiency.…”