Highly efficient second-harmonic generation from indefinite epsilon-near-zero slabs of subwavelength thickness

TL;DR

This paper theoretically predicts highly efficient second-harmonic generation in ultra-thin indefinite epsilon-near-zero slabs, leveraging large longitudinal field enhancements for nonlinear optical applications.

Contribution

It introduces a novel approach using indefinite epsilon-near-zero slabs for efficient SHG, with a specific nano-structured composite design for experimental realization.

Findings

High SHG efficiency from subwavelength slabs predicted theoretically.

Efficiency driven by large longitudinal field enhancement near transparency conditions.

Design of nano-structured composite for experimental observation proposed.

Abstract

We theoretically predict efficient optical second-harmonic generation (SHG) from a few hundred nanometer thick slab consisting of a quadratic nonlinear anisotropic medium whose linear principal permittivities are, at the fundamental wavelength, very small and have different signs (indefinite medium). We show that, by illuminating the slab with a p-polarized fundamental wave (with intensity of a few MW/cm^2), a highly efficient scattering of the second-harmonic field occurs when the conditions of linear complete slab transparency for the fundamental wave are met. The high efficiency of the SHG process, stems from the large non-plasmonic enhancement of the longitudinal field, perpendicular to the slab surface, produced by the very small value of the slab dielectric permittivities. A suitable nano-structured composite is proposed and numerically designed for observing the novel non-phase-matched and highly efficient SHG process from nano-structures.