Femtosecond laser-induced sub-wavelength plasma inside dielectrics: III. Terahertz radiation emission

TL;DR

This paper investigates how femtosecond laser-induced plasmas inside dielectrics can emit terahertz radiation, revealing the role of electrostatic fields and electron populations through simulations and analysis.

Contribution

It demonstrates the mechanism of THz radiation emission from laser-induced plasmas in dielectrics, combining 3D simulations with analytical insights.

Findings

THz radiation is emitted at the critical surface due to electrostatic fields.

Hot electron populations trapped in ambipolar electric fields are responsible for the emission.

Resonantly driven electrostatic fields facilitate THz generation.

Abstract

Electromagnetic radiation within the terahertz (THz) frequency range is of great interest for applications in remote sensing and time-domain spectroscopy. The laser-induced plasmas are promising mediums for generating THz radiation. It has been recently reported that focusing femtosecond Bessel pulses inside dielectrics induces a high aspect ratio over-critical plasmas. Here we show that the intense resonantly driven electrostatic fields at the so-called critical surface lead to THz radiation emission. Through three-dimensional particle-in-cell simulation and analytical derivation, we have investigated the emission of THz radiation. We show that the THz radiation is associated with a hot population of electrons trapped in ambipolar electric fields of the double layers.