Optical Activation of Germanium Plasmonic Antennas in the Mid Infrared

TL;DR

This paper demonstrates that femtosecond near-infrared pulses can activate germanium plasmonic antennas in the mid-infrared range, enabling ultrafast optical switching through plasma response modulation.

Contribution

It introduces a novel method to optically activate germanium plasmonic structures for mid-infrared applications using impulsive interband excitation.

Findings

Plasmonic resonance can be optically activated in germanium structures.

Activation lasts for hundreds of picoseconds before charge recombination occurs.

The behavior is accurately modeled by electron-hole plasma electrodynamics.

Abstract

Impulsive interband excitation with femtosecond near-infrared pulses establishes a plasma response in intrinsic germanium structures fabricated on a silicon substrate. This direct approach activates the plasmonic resonance of the Ge structures and enables their use as optical antennas up to the mid-infrared spectral range. The optical switching lasts for hundreds of picoseconds until charge recombination red-shifts the plasma frequency. The full behavior of the structures is modeled by the electrodynamic response established by an electron-hole plasma in a regular array of antennas.