# All-optical switching and unidirectional plasmon launching with electron-hole plasma driven silicon nanoantennas

## TL;DR

This paper introduces a novel silicon nanoantenna design that enables tunable all-optical switching and unidirectional plasmon launching through electron-hole plasma photoexcitation, advancing nonlinear nanophotonics.

## Contribution

The work presents a new geometry for silicon nanoantennas that allows efficient tuning of radiation properties via electron-hole plasma photoexcitation, enabling ultrafast all-optical modulation and unidirectional plasmon launching.

## Key findings

- Nanoantenna radiation patterns can be dramatically altered by low-intensity pumping.
- Ultrafast pumping achieves unidirectional surface plasmon-polariton launching.
- Tuning of Van Hove singularity enhances all-optical modulation capabilities.

## Abstract

High-index dielectric nanoparticles have become a powerful platform for modern light science, enabling various fascinating applications, especially in nonlinear nanophotonics for which they enable special types of optical nonlinearity, such as electron-hole plasma photoexcitation, which are not inherent to plasmonic nanostructures. Here, we propose a novel geometry for highly tunable all-dielectric nanoantennas, consisting of a chain of silicon nanoparticles excited by an electric dipole source, which allows tuning their radiation properties via electron-hole plasma photoexcitation. We show that the slowly guided modes determining the Van Hove singularity of the nanoantenna are very sensitive to the nanoparticle permittivity, opening up the ability to utilize this effect for efficient all-optical modulation. We show that by pumping several boundary nanoparticles with relatively low intensities may cause dramatic variations in the nanoantenna radiation power patterns and Purcell factor. We also demonstrate that ultrafast pumping of the designed nanoantenna allows unidirectional launching of surface plasmon-polaritons, with interesting implications for modern nonlinear nanophotonics.