Extreme THz fields from two-color filamentation of mid-infrared laser pulses

TL;DR

This paper demonstrates a method using two-color filamentation of mid-infrared laser pulses to generate extremely strong single-cycle THz pulses with high efficiency, enabling new frontiers in extreme field science.

Contribution

It introduces a novel approach for high-energy THz generation using mid-infrared pulses, achieving unprecedented field strengths and efficiencies.

Findings

Generated multi-millijoule THz pulses with high conversion efficiency.

Achieved electric fields of GV/cm and magnetic fields of kT, surpassing existing sources.

Identified a new harmonic-based mechanism for symmetry breaking in THz generation.

Abstract

Nonlinear THz photonics is probably the last frontier of nonlinear optics. The strength of both the electric and the magnetic fields of these ultrashort low frequency light bunches opens the way to exciting science and applications. Progress in the field though is slow because of the deficiency in suitable sources. Here we show that two-color filamentation of mid-infrared 3.9 um laser pulses allows one to generate single cycle THz pulses with multi-millijoule energies and extreme conversion efficiencies. Moreover, the focused THz peak electric and magnetic fields reach values of GV/cm and kT, respectively, exceeding by far any available quasi-DC field source today. These fields enable extreme field science, including into other, relativistic phenomena. Besides, we elucidate the origin of this high efficiency, which is made up of several factors, including a novel mechanism where the harmonics produced by the mid-infrared pulses strongly contribute to the field symmetry breaking and enhance the THz generation.