Terahertz emission from laser-driven gas-plasmas: a plasmonic point of view

TL;DR

This paper reveals how plasmonic resonances in laser-induced gas-plasmas can significantly enhance and broaden terahertz emission spectra, controllable via laser polarization and beam shape, supported by experiments and simulations.

Contribution

It uncovers a novel link between plasmonics and terahertz generation in gas-plasmas, demonstrating control over emission spectra through laser polarization and geometry.

Findings

Plasmonic resonances broaden terahertz spectra.

Resonances are identified as leaky modes.

Beam shape influences pulse duration and spectral width.

Abstract

We disclose an unanticipated link between plasmonics and nonlinear frequency down-conversion in laser-induced gas-plasmas. For two-color femtosecond pump pulses, a plasmonic resonance is shown to broaden the terahertz emission spectra significantly. We identify the resonance as a leaky mode, which contributes to the emission spectra whenever electrons are excited along a direction where the plasma size is smaller than the plasma wavelength. As a direct consequence, such resonances can be controlled by changing the polarization properties of elliptically-shaped driving laser pulses. Both, experimental results and 3D Maxwell consistent simulations confirm that a significant terahertz pulse shortening and spectral broadening can be achieved by exploiting the transverse driving laser beam shape as an additional degree of freedom.