Air nonlinear dynamics initiated by ultra-intense lambda-cubic THz pulses

TL;DR

This paper demonstrates significant nonlinear effects in air caused by ultra-intense Terahertz pulses, enabling new phenomena like self-focusing and filamentation at these frequencies.

Contribution

It reports the first observation of large-amplitude nonlinearity in air at Terahertz frequencies induced by intense light bullets.

Findings

Observation of strong air birefringence at THz frequencies

Identification of third order susceptibility in air

Potential for THz-induced self-focusing and filamentation

Abstract

Air turns into a nonlinear medium for electromagnetic waves under exceptionally strong fields. However up to present, its minuscule nonlinear response has limited the exploration to the optical frequency regime owing to the availability of intense near-infrared lasers. Here, we report on the observation of large-amplitude nonlinearity in air induced by an extremely intense light bullet at Terahertz frequencies (0.1-10 THz) provoking strong air birefringence. The observed nonlinearity manifests itself as third order susceptibility. The presented nonlinear observations break the barrier for the entire exciting THz-induced nonlinear phenomena in air ranging from THz-induced self-focusing and self-phase modulation to THz solitons and filamentation.