Low-damping epsilon-near-zero slabs: nonlinear and nonlocal optical properties

TL;DR

This paper explores nonlinear and nonlocal optical effects in epsilon-near-zero metamaterial slabs with gain media, demonstrating enhanced second harmonic generation, multistability, and all-optical switching due to damping compensation and leaky mode excitation.

Contribution

It introduces a novel approach to enhance nonlinear optical properties in ENZ metamaterials by using gain media and analyzing nonlocal effects caused by leaky modes.

Findings

Enhanced second harmonic generation near pseudo-Brewster angle

Observation of low-threshold multistability and all-optical switching

Identification of nonlocal effects mediated by leaky modes

Abstract

We investigate second harmonic generation, low-threshold multistability, all-optical switching, and inherently nonlocal effects due to the free-electron gas pressure in an epsilon-near-zero (ENZ) metamaterial slab made of cylindrical, plasmonic nanoshells illuminated by TM-polarized light. Damping compensation in the ENZ frequency region, achieved by using gain medium inside the shells' dielectric cores, enhances the nonlinear properties. Reflection is inhibited and the electric field component normal to the slab interface is enhanced near the effective pseudo-Brewster angle, where the effective \epsilon-near-zero condition triggers a non-resonant, impedance-matching phenomenon. We show that the slab displays a strong effective, spatial nonlocality associated with leaky modes that are mediated by the compensation of damping. The presence of these leaky modes then induces further spectral and angular conditions where the local fields are enhanced, thus opening new windows of opportunity for the enhancement of nonlinear optical processes.