Coherent generation and control of tunable narrowband THz radiation from laser-induced air-plasma filament

TL;DR

This study demonstrates a method to generate tunable, narrowband, CEP-controlled THz radiation from air plasma using a two-color laser pulse sequence with experimental and numerical validation.

Contribution

It introduces a novel approach for coherent control of narrowband THz generation from air plasma with high tunability and CEP control.

Findings

Successful generation of CEP-controllable narrowband THz radiation.

Experimental and numerical results agree on the nonlinear interaction mechanisms.

High tunability of THz frequency achieved through pulse sequence manipulation.

Abstract

We report on the proof-of-principle experiment of generating carrier-envelope phase (CEP)-controllable and frequency-tunable narrowband terahertz (THz) radiation from air-plasma filament prescribed by the beat of temporally stretched two-color laser pulse sequence. The pulse sequence was prepared by propagating the fundamental ultrafast laser pulse through a grating stretcher and Michelson interferometer with variable inter-arm delay. By partially frequency-doubling and focusing the pulse sequence, an air-plasma filament riding a beat note was created to radiate THz wave with primary pulse characteristics (center frequency and CEP) under coherent control. To reproduce experimental results and elucidate complex nonlinear light-matter interaction, numerical simulation has been performed. This work demonstrates the feasibility of generating coherently controlled narrowband THz wave with high tunability in laser-induced air plasma.