Terahertz Radiation from Laser-Ionized Plasmas

TL;DR

This paper demonstrates through simulations that laser-ionized plasmas can generate terahertz electromagnetic pulses with characteristics determined by plasma parameters, revealing new insights into laser-plasma energy transfer mechanisms.

Contribution

It introduces a combined simulation and modeling approach to understand terahertz pulse generation from laser-ionized plasmas, highlighting the dependence on pulse length and plasma frequency.

Findings

Terahertz pulses radiate with frequency set by plasma frequency.

Energy losses to wakefield are independent of pulse width when matching plasma wavelength.

Losses to EMP decrease as pulse width increases.

Abstract

Numerical simulations of laser-plasma interactions demonstrate the generation of axially polarized electromagnetic pulses (EMPs) that radiate away energy with a characteristic frequency determined by the plasma frequency, in the THz range for typical laser wakefield acceleration experiments. This is confirmed by full 2D electromagnetic particle-in-cell simulations, as well as by a ponderomotively-driven reduced model that captures the EMP generation essentials. When the laser's pulse length matches the plasma wavelength, that pulse's fractional energy losses to the wakefield are independent of the pulse width, while the losses to the EMP are inversely dependent on the pulse width.