Coherent synthesis of terahertz radiation from femtosecond laser filaments in air

Abstract

International audienceWe report on the coherent synthesis of pulsed terahertz radiation from femtosecond laser filaments organized in an array. The terahertz intensity is proportional to the square of the number of the filaments, which provides a simple method for scaling up of the terahertz energy with a powerful femtosecond laser. Moreover, directional off-axis terahertz radiation can be achieved. This paves the way for applications of this terahertz source for remote sensing

Effect of an external electric field on the coherent terahertz emission from multiple filaments in air

“…Note that there is no decrease of the THz intensity within the range studied here. This differs from the results obtained in the absence of an electric field [12], where the THz intensity starts to decrease with the increase of the spatial separation between filaments. We attribute it to the different size of the intersection areas of two THz radiation patterns from each individual filament with and without external electric field.…”

“…Terahertz (THz) radiation from plasma in air induced by laser pulses was first demonstrated by Hamster and co-workers about 20 years ago [1]. Since then, the THz radiation from a long plasma channel, a filament, generated by an intense femtosecond laser has attracted much attention [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. For a filament formed by a single femtosecond laser pulse, the THz radiation is produced by the longitudinal plasma oscillations in the wake of the moving ionization front.…”

“…In our previous letter [12], we have shown that it is possible to add coherently the THz emission from multiple filaments, leading to an increase of the radiated THz energy scaling like N², where N is the number of filaments. In this letter, we consider experimentally and theoretically the effect of a static electric field on the THz emission from multiple filaments.…”

Revealing plasma oscillation in THz spectrum from laser plasma of molecular jet

“…Broadband ultrashort terahertz (THz) pulses are generated from the laser induced plasma by two-color pulses, and it is under intensive studies owing to the potential to produce high intensity THz field and achieve the off-site detection in air [1][2][3][4][5][6][7]. From the plasma filament pumped by the two-color laser pulses, the directional photocurrents generate the enhanced supercontinuum at the THz wavelength range with the conversion efficiency two orders larger than that from single color intense laser field [8,9].…”

Terahertz generation from single and multiple filaments in air

“…We have shown that a 2D array of multiple plasma filaments in atmospheric density gases leads to the efficient increase of terahertz radiation emitted in the forward direction. As the number of filaments in an N × N array is augmented, the THz energy increase per unit polar angle in the central cone exceeds the standard gain factor N 2 [4,5]. The two-dimensional multiple filament array can be produced from an actu-EPJ Web of Conferences 195, 03013 (2018) https://doi.org/10.1051/epjconf/201819503013 TERA-2018 al non-ideal elliptical beam using a phase plate to introduce a phase barrier and block the interaction between the neighboring filaments.…”