All-optical switching of an epsilon-near-zero plasmon resonance in indium tin oxide

Justus Bohn,Ting Shan Luk,Craig Tollerton,Simon Horsley,Euan Hendry,William L Barnes,Igal Brener,Sam W Hutchings

doi:10.1038/s41467-021-21332-y

Abstract

Nonlinear optical devices and their implementation into modern nanophotonic architectures are constrained by their usually moderate nonlinear response. Recently, epsilon-near-zero (ENZ) materials have been found to have a strong optical nonlinearity, which can be enhanced through the use of cavities or nano-structuring. Here, we study the pump dependent properties of the plasmon resonance in the ENZ region in a thin layer of indium tin oxide (ITO). Exciting this mode using the Kretschmann-Raether configuration, we study reflection switching properties of a 60 nm layer close to the resonant plasmon frequency. We demonstrate a thermal switching mechanism, which results in a shift in the plasmon resonance frequency of 20 THz for a TM pump intensity of 70 GW cm−2. For degenerate pump and probe frequencies, we highlight an additional two-beam coupling contribution, not previously isolated in ENZ nonlinear optics studies, which leads to an overall pump induced change in reflection from 1% to 45%.

Highlights

Nonlinear optical devices and their implementation into modern nanophotonic architectures are constrained by their usually moderate nonlinear response
Nonlinear optics is utilized for a wide range of photonic applications such as quantum all-optical data processing[1,2], information technology[3,4] and telecommunication applications
We identify two contributions to the nonlinear signal: A dominant thermal switching process results in a shift in the plasmon resonance frequency of 20 THz for a TM pump intensity of 70 GW cm−2 when pumping resonantly, resulting in a change in reflection of the probe from 1 to 30%

Summary

Introduction

Nonlinear optical devices and their implementation into modern nanophotonic architectures are constrained by their usually moderate nonlinear response. With the rise of new computational demands such as artificial intelligence, all-optical signal processing is often seen as a breakthrough technology for the generation of computation and communication devices[5] Such applications are limited by the interaction of light signals, with extremely weak optical nonlinearity exhibited by most materials. One can excite plasmons using a high index incident prism in the Kretschmann–Raether configuration, circumventing the need for nano-structuring or the additional support of a cavity. This approach has been employed to study plasmon-based nonlinear optical dynamics in gold films[32,33,34]

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