Understanding the nonlinear optical response of epsilon near zero materials in the time-domain

TL;DR

This paper develops a self-consistent time-domain model to understand and simulate the nonlinear optical response of epsilon-near-zero materials, specifically TCOs like ITO, enabling improved nanophotonics design.

Contribution

It introduces a novel time-domain modeling approach for nonlinear epsilon-near-zero materials and validates it against experimental data, advancing nanophotonics simulation capabilities.

Findings

Validated model matches experimental results for ITO films.

Demonstrated nonlinear enhancement in ITO-based metasurfaces.

Enabled quantitative design of nanophotonic devices using epsilon-near-zero materials.

Abstract

The promise of active nanophotonics technology relies on the confinement and control of light at the nanoscale. Confinement via plasmonics, dielectric resonators, and waveguides can be complemented with materials whose optical properties can be controlled using nonlinear effects. Transparent conducting oxides (TCOs) exhibit strong optical nonlinearities in their near zero permittivity spectral region, on the femtosecond time-scale. Harnessing full control over the nonlinear response requires a deeper understanding of the process. To achieve this, we develop a self-consistent time-domain model for the nonlinear optical response of TCOs and implement it into a three-dimensional finite-difference time-domain code. We compare and tune our simulation tools against recently published experimental results for intense laser irradiation of thin indium tin oxide (ITO) films. Finally, by simulating intense laser irradiation of ITO-based plasmonic metasurfaces, we demonstrate the full power of our approach. As expected, we find validating the significant enhancement of the nonlinear response of an ITO-based metasurface over bare ITO thin films. Our work thus enables quantitative nanophotonics design with epsilon-near-zero materials.