# Dynamically reconfigurable metal-semiconductor Yagi-Uda nanoantenna

## TL;DR

This paper introduces a tunable Yagi-Uda nanoantenna made of metal-dielectric core-shell nanoparticles, capable of operating in two regimes with high directivity and dynamic control via ultrafast electron-hole plasma excitation.

## Contribution

It presents a novel hybrid nanoantenna design that can switch between two operational regimes with enhanced emission properties and tunability using ultrafast optical pulses.

## Key findings

- Dual operational regimes with high directivity and Purcell factor.
- Dynamic tuning of emission pattern via femtosecond pump pulses.
- Potential for flexible, high-performance nanoantenna applications.

## Abstract

We propose a novel type of tunable Yagi-Uda nanoantenna composed of metal-dielectric (Ag-Ge) core-shell nanoparticles. We show that, due to the combination of two types of resonances in each nanoparticle, such hybrid Yagi-Uda nanoantenna can operate in two different regimes. Besides the conventional nonresonant operation regime at low frequencies, characterized by highly directive emission in the forward direction, there is another one at higher frequencies caused by hybrid magneto-electric response of the core-shell nanoparticles. This regime is based on the excitation of the van Hove singularity, and emission in this regime is accompanied by high values of directivity and Purcell factor within the same narrow frequency range. Our analysis reveals the possibility of flexible dynamical tuning of the hybrid nanoantenna emission pattern via electron-hole plasma excitation by 100 femtosecond pump pulse with relatively low peak intensities $\sim$200 MW/cm$^2$.